Engineer S. Balakshin

ELECTRIFICATION

OF MILLS

“Steam plant are doomed
in the milling industry”

Tomsk

1930

Contents

	Page
Introduction	1
Chapter I. The present state of electrification of mills in the USSR	5
Chapter II. Technical foundations of mill electrification	→
Energy consumption by various types of mills and its distribution	10
Chapter III. Transmission of power from the mill by electricity	—
Direct-current motors	35
Alternating-current motors	37
General arrangement of electric transmission in flour mills	59
Chapter IV. Electric lighting of mills	65
Chapter V. Economic foundations of mill electrification	81
Chapter VI. Examples of mill electrification	92
Chapter VII. Electrification of agricultural mills	109
Chapter VIII. Prospects for the electrification of mills	104
Chapter IX. Conclusion	110
Appendix. General data and tables	111
Résumé	117
Literature on the electrification of mills	119
Alphabetical index	120

PREFACE

The complete reconstruction of the industrial economy of the USSR on new socialist principles, with the implementation of a broad plan for the electrification of the entire republic, has urgently raised the question of the electrification of our mills.

The rapid growth of mill electrification and the need to have data elucidating this question, in the almost complete absence of literature in Russian on this subject, were the reason for the appearance of the author’s present work.

By the electrification of mills one should, strictly speaking, understand not only the transition of mill machines and mechanisms to electric drive and the use of electric lighting, but also, in general, the broadest application of electrical energy in flour milling—for example, its use for removing dust, electric sieves, etc.; but since in practice this is still a matter for the future, the author has devoted primary attention only to the first two questions.

In the present work the author’s aim was chiefly to acquaint workers in the flour-milling field with this comparatively new and extremely important problem, providing both a general introduction and the principal technical and economic data for the transition to electric power and for the operation of electrified mills.

In view of the fact that the question of the expenditure of energy for driving a mill and its distribution is of chief importance in electrification, special attention has been devoted to it, with the presentation of a number of data and generalizing conclusions for mills of both the agricultural type and the commercial type.

The author also wished in this work to provide students studying flour milling with an aid in designing the electrification of mills.

As head of the Department of Flour Milling at the Siberian Technological Institute in Tomsk and having experience in the construction of mills, the author made use, as far as possible, of his familiarity with questions of flour milling and power engineering, also making extensive use of the latest literature—especially foreign literature—and of successes and experience abroad.

In the present work it was also desirable to give a number of practical data relating to the electrification of mills in the USSR, which was made possible thanks to the assistance of our largest economic organizations, “GET” and “Soyuzkhleb,” which stand in the vanguard of carrying out the electrification of mills in the Republic.

For supplying these valuable data I consider it necessary here to express my gratitude to the head of the Construction Administration of Soyuzkhleb in Moscow, K. D. Lel, and to the engineers V. I. Kuznetsky and I. B. Manasevich; to the manager of the Industrial Installations Department of “GET” in Moscow, engineer G. P. Levi, and to engineer L. G. Zilov.

Undoubtedly, these data, together with the latest data from foreign literature, will be of particular interest to readers in the USSR.

If this work convinces even a few workers in the flour-milling field of the need for the earliest possible transition of mills to electric power, and serves as an impetus for carrying out their electrification in the near future, and helps students, then the author will consider himself satisfied.

The author is fully aware that this work of his, being the first attempt to illuminate the question of the electrification of mills as a whole, has a number of shortcomings and omissions, and he will be grateful to all who send him their comments in this regard.

Associate Professor S. Balakshin.

Tomsk, January 1930.

INTRODUCTION

The importance of power engineering for the flour-milling industry. A brief history of it. The importance of the electrification of mills. The power economy of the factory-and-plant industry of the USSR and its comparison with the power economy of the chief Western countries. General characteristics of the flour-milling industry of the USSR.

“Cheap and reliable power has always
been of first concern in flour milling” *).

From time immemorial, the conversion of grain into flour has presented mankind with a mass of cares and difficulties, since this process requires a rather considerable expenditure of energy. Initially grain was pounded in mortars; then hand millstones began to be used, employing slaves for the work.

The great difficulties involved in grinding grain were one of the first impulses toward the invention of engines.

Water wheels and windmills appeared; then came the more powerful steam engine, independent of place and time, internal-combustion engines, and roller milling. This type of mill, with mechanical transmission of motion directly from engines located near the mills, predominated, and in some countries, including our own, in the USSR, still predominates to this day.

But then transmission by means of electricity appears. At first very primitive and imperfect, in recent decades it has attained a high degree of perfection. It becomes possible to transmit energy from large central power stations, often located directly at the sources of energy, over hundreds of kilometers. A mass of conveniences is created in the installation and operation of industrial enterprises, and energy is obtained at a very low cost. The flour-milling industry, where expenditure on energy constitutes one of the principal component parts of the cost of milling, begins at first cautiously, and then ever more rapidly, to shift—especially in America—to electric power. And it is enough to say that at the present time in the U.S.A. more than half of all mills are already electrified.

In the form of electricity, flour mills have received not only a universal, cheap, convenient-to-use energy; for them there has also appeared the possibility not only of using this energy according to need, but, in certain combinations, at moments of stoppage and when they have their own engines, even of returning this energy back. Thus, in the largest flour-milling center of America, the city of Minneapolis, there are mills where a synchronous alternating-current electric motor, driven by the energy of a central power station, has its rotor mounted on one shaft with the runner of a water—

*) Cheap and conveniently applicable energy has always been the first fundamental condition for the development of the flour-milling industry.

of the turbine, can by a simple switching be converted into a generator, which can supply energy to other mills or rotate the station backward when the mill has no grinding to do, while these switchings are made automatically, without the participation of human hands. The transmission of energy to flour mills by electricity is at present so technically perfected and convenient and so economically advantageous that the question of the broad electrification of mills is one of the most urgent questions.* “Steam plant are doomed in the milling industry” (steam installations have outlived their time in mills), say the Americans.

Undoubtedly, in our USSR as well the question of the electrification of mills, especially in connection with the implementation of the broad plan for the electrification of the entire country, is fully ripe. True, as we shall see below, electric motors are already being used in mills, and electrified mills are even appearing (Dnepropetrovsk, Tashkent, and others), but so far the use of electrical energy in the flour-milling industry as a whole is still very insignificant, amounting to only 5.8%, and in this respect, in the very near future, much work lies ahead of us, as indeed in the field of power engineering and electrification in general.

To illustrate this, we shall cite here a number of figures on the power economy of industry, borrowed by us from the recently published valuable work of our Central Statistical Administration: Factory and Plant Industry of the USSR (Moscow, 1929).

The power economy of the industry of the USSR and its comparison
with the power economy of the main Western countries.

Before proceeding to characterize the state of the electrical economy of the flour-milling industry of the USSR, we shall present the principal data characterizing the power economy of the factory and plant industry of the USSR as a whole.

According to the data of the C.S.A., the total capacity of the operating engines installed in the factory and plant industry of the Union at the beginning of 1926–27 was 2,010 thousand h.p. ** (in all, 2,495 thousand h.p., i.e., the nonoperating portion was 1/5). In addition, there were installations at public electric power stations with a total capacity of 859.0 thousand h.p. Thus, the indicator illustrating the centralization of our power economy, consisting in the ratio of the capacity of the prime movers of public electric stations to the capacity of the prime movers installed in industry at the beginning of 1926–27, was 1:0.304; or the capacity of the prime movers in industry was 74.3%, and that of public electric stations 25.7%.

About 3/5 of the capacity of engines serving working machines falls, in industry, on electric drive, and about 2/5 on mechanical drive.

* For clarity we add that it is understood that this mill, of course, first of all uses the energy of its water engines, applying electrical energy in case of a shortage of water.

* C.S.A., Factory and Plant Industry of the USSR*, issue 2, p. 10.

Table No. 1.

Comparative characteristics of the energy base of industry in the USSR and the principal Western countries.

No.	NAME OF COUNTRIES	Total capacity of engines serving working machines (through mechanical and electrical drives), in thousands of h.p.	Level of electrification; ratio of the capacity of electric-station engines in industry to the capacity of engines of public-use electric stations	Capacity of primary engines of power stations for public use, in thousands of h.p.	Capacity of primary engines of power stations for public use, relative to USSR
1	USSR, 1925–26	3.410	1 : 0.30	859	1
2	U.S.A., 1925	36662	1 : 1.63	32600	38
3	England, 1924	14868	1 : 0.56	5382	6.3
4	Germany, 1925	18099	—	7031	8.2
5	Norway, 1925	684	1 : 3.94	1514	1.8
6	Sweden, 1925	1532	1 : 1.15	1020	1.2
7	Canada, 1924	—	1 : 1.81	2424	2.8

Table No. 1 presents a comparative characterization of the energy base of industry in the USSR and the principal Western countries. It is plainly evident from it “that the initial bottleneck in our energy sector, as compared with the world energy sector, is, in the final analysis, the comparatively insignificant—both in absolute and relative terms—magnitude of the capacity falling to power stations. In this determining fact lie the principal reasons why we occupy a place in the last rank according to the most important indicators that qualitatively characterize the energy base of the country.

Herein lie the roots of the comparative insignificance of the national-economic efficiency of the entire energy system of our industry in comparison with the advanced countries of the world economy. Here undoubtedly are also embedded the roots of a number of basic factors slowing the principal tempo of the unfolding curve of industrialization of our national economy.

Until the reconstruction process shifts the center of gravity of the energy axis of the national economy closer to the system of planned super-power stations; until the latter dominate in the energy economy of our country—we shall still trail at the tail of the energy sector of the advanced countries of the world. But all the basic data are present in the Soviet country for crossing this Rubicon in the nearest period and for moving the energy link of the country’s productive forces onto the highest technical foundation and thereby taking a place in the first rank of world-economic energy.”

Thus we face the great task of carrying out the broad electrification of industry, including the flour-milling industry, as one of the largest consumers of energy.

The energy economy of the flour-milling industry of the USSR and its role in the energy economy of all factory and plant industry of the Union.

Having set forth above the general data on the energy economy of the industry of the USSR and its comparison with the energy economy of the principal Western countries, we shall, using the same materials of the Central Statistical Administration, present here data characterizing the state of the energy economy of the flour-milling industry ) in 1926–27*, and compare it with the general energy economy of all factory and plant industry of the USSR. Table No. 2 gives a general characterization of the flour-milling industry studied. It shows that the total capacity of the power apparatus of the flour-milling industry amounted to 6.7% of the capacity of the power apparatus of all industry of the USSR, while gross output was 8.3%, which indicates the significance of the flour-milling industry.

Table No. 2.

General characterization of the flour-milling industry of the USSR
at the beginning of 1926–27.

No.	Indicator	Flour-milling industry of the USSR — Total	Flour-milling industry of the USSR — In % of all industry of the USSR	All factory and plant industry of the USSR
	Total number of flour mills	1564	18.4%	8533
	Average number of workers	39810	1.9%	2091451
	Man-days worked, in thousands	8523	1.53%	558990
	Man-hours worked, in thousands	66262	1.57%	4239821
	Total capacity of the power apparatus, in effective h.p.	185147	6.7%	2765002
	Gross turnover, in thousand rubles	843388	6.5%	13123404
	Gross output, in thousand rubles	824129	8.3%	9934063
	Idle establishments with engines	98	—	617
	Idle establishments without engines	16	—	462

*) Commercial flour milling.

CHAPTER I

The State of Electrification of Mills in the USSR at the Present Time

Composition of electric drives. Distribution of energy. Principal indices of power supply and electrification of industry. Coefficients of utilization of apparatus.

Having presented above the general data on the power supply of factory industry, let us now consider the present state of the electrification of the power economy of our mills and of all our factory industry. Table No. 3 gives data on electric generators and electric motors at mills of the USSR. It shows that the total number of electric motors

Table No. 3.

Composition of electric drives in the flour-milling industry and in all industry of the USSR at the beginning of 1926–27.

	Flour-milling industry	In % of all industry	In % of this branch of industry	All industry	In % of all industry
I. Electric generators.
1. Total.
Number	986	—	—	6971	—
Power, kW	17939	2,3	—	782966	100,0
I. Including those in operation.
A) Total.
Number	972	—	—	6860	—
Power, kW	17535	—	—	774927	—
II. Electric motors.
1. Total.
Number	578	—	0,548%	103528	—
Power, kW	16030	1,1	1,105%	1449530	—
Including those in operating establishments.
Number	574	—	—	102983	—
Power, kW	15918	—	—	1439251	100,0
Including
A) using their own current:
Number	335	—	—	46153	—
Power, kW	6677	41,7	—	794646	51,8
			100%

	Flour-milling industry	In % of the entire industry	In % for this branch of industry	All industry	In % of the entire industry
B) Purchased current:
Number	243	—	—	52144	—
Power, kW	9353	58.3	—	570016	39.3
C) Mixed current:
Number	—	—	—	5231	—
Power, kW	—	—	—	84868	5.9

at operating mills there are 578, which amounts to 0.548% of the total number (102983) of electric motors*) in all industry. All 578 electric motors have a total power of 16030 kW, which amounts to 1.105% of the total power (1,439,251 kW) of electric motors in all industry of the USSR.

Table No. 4 gives the consumption of energy. From it one can see that, of the total amount of energy of 594,596 thousand horse-power hours used in 1925–26 for production purposes in the flour-milling industry, electric energy amounted to 34,469.1 thousand h.p.-hours, or 5.8%, while for all industry of the USSR it was 6,317,614.2 thousand h.p.-hours, including electric energy 2,867,973.5 thousand h.p.-hours, or 45.5%.

Hence it is clear that the flour-milling industry, in comparison with other branches of industry of the USSR, is still extremely little electrified.

Table No. 4.

Energy consumption in the flour-milling and factory-plant industry of the U.S.S.R.

No.		Flour-milling industry	Flour-milling industry, %	All industry of the USSR	All industry of the USSR, %
	Energy consumed for production purposes, in thousand horse-power-hours.
	I. For servicing working machines.
1	Mechanical energy	560,095.9	—	3,449,640.7	—
	electric (motor) energy
2	Own	5,988.6	—	1,837,944.2	—
3	Purchased	27,172.3	—	978,341.6	—
4	Total	32,166.9	—	2,816,285.8	—
5	Total for servicing working machines	593,256.8	—	3,265,926.5	—
6	Electric, non-motor	1,308.2	—	51,687.6	—

) Collection of the C.S.U., p. 208, table 2 A.
*) Table 2A, p. 119.

Nos.	Type of indicators	Flour-milling industry	Flour-milling industry %	Entire industry of the USSR	Entire industry of the USSR %
7	Total for production purposes	594565,0	100%	6317614,2	100%
8	Including electric power	34460,1	58%	28679735	45,5%
9	II. Electric power consumed for economic needs	14345,4	—	271949,5	—
10	Total energy consumed, in thousand horse-power-hours	608910,4	—	6589563,7	—
11	Including electric power: own	20230,1	—	2057384,5	—
12	Purchased	28587,3	—	1082558,1	—
13	Energy supplied to outside consumers	2220,4	—	248623,3	—
14	Energy losses	2469,8	—	253812,5	—
15	Total expenditure of energy, in thousand horse-power-hours	613600,6	—	7091999,5	—

Table No. 5 gives the principal indicators of the energization of labor and the electrification of industry. It shows that the potential coefficient of the energization of labor, expressed as the ratio of the power of the motors intended to service working machines to the number of industrial workers, is 10,94 for the flour-milling industry and 2,74 for the entire industry of the USSR.

The actual coefficient of energization is the ratio of the energy actually consumed for production purposes to the number of hours actually worked by production workers—respectively 11,86 and 1,88. Hence it is clear, as indeed should have been assumed, that the coefficient of energization of labor in the flour-milling industry is considerably higher than the average for the entire factory-and-plant industry of the USSR.

Table No. 5.

Principal indicators of the energization of labor and the electrification of industry*).

Nos.	Type of indicators	Flour-milling industry of the USSR	Entire industry of the USSR
	I. Coefficient of energization of labor, A. Potential:
1	Ratio of the power of motors of working machines to the number of production workers in 1 shift	10,94	2,74
	B. Actual:
2	Ratio of energy expended for production purposes to the number of hours worked by production workers	11,86	1,88

*) p. 171, table 2-A Ts.S.U.

No.	INDICATORS	Flour-milling industry of the USSR	All industry of the USSR
	II. Electrification coefficients in %. A. Potential (by capacity).
3	1. Ratio of the capacity of generators to the capacity of prime movers	12.7%	44.3%
4	2. Ratio of the capacity of all electric motors to the capacity of the engines intended to serve working machines	11.6%	59.6%
	B. Actual (by operation).
5	1. Ratio of all electric energy (one’s own and outside) to all energy (generated by prime movers + received from outside)	8.7%	51.4%
6	2. Ratio of the energy converted into electric energy to all energy generated by prime movers	4.3%	42.5%
7	3. Ratio of motor energy to the energy consumed by the engines intended to serve working machines	5.6%	44.9%

If, however, we compare these coefficients with the coefficients of power mechanization for foreign mills, they will be still higher there.

Kupritz*) calls the potential coefficient of power mechanization of labor the coefficient of mechanization, and gives the following figures: for Germany, from 8 to 13 h.p.; for the U.S.A., where in 1925 commodity mills had 669,910 h.p. with 31,988 production workers, or 21 h.p. per worker.

As regards the electrification coefficients of the mills of the USSR, then, as is evident from Table No. 5, the potential electrification coefficient, i.e. the ratio of the capacity of all electric motors to the capacity of the engines intended to serve working machines, amounts to 11.6% for the flour-milling industry of the USSR and 59.6% for all industry.

The actual electrification coefficient (by operation), i.e. the ratio of all electric energy (one’s own + outside) to all energy (generated by prime movers + received from outside), is 8.7% for flour milling and 51.4% for all industry of the USSR.

These figures show us the considerable backwardness of electrification in our flour-milling industry, especially if we recall that in the U.S.A. more than 50% of all mills are already electrified.

Load factor of the power equipment of the flour-milling industry of the USSR.

The load factors of power equipment are also of interest. Here three types of these coefficients may be distinguished**).

) Kupritz. Rational Mill, p. 192.
) Factory-Plant Industry of the USSR*, issue 2, p. 104.

1. Integral load factor.

\[ = \frac{\text{Average actual power} \times \text{Number of working hours}} {\text{Working power} \times 8760\;(\text{number of hours in a year})} \]

1. Intensive load factor.

\[ = \frac{\text{Average actual power}} {\text{Power of the motors that were operating}} \]

1. Extensive factor.

\[ = \frac{\text{Number of hours of operation}}{8760} \]

Note: 8760 is the number of hours in a year.

It is thus obvious that:

Integral factor = intensive factor × extensive factor.

It is also obvious that the integral factor is nothing other than the utilization factor of the power installation, as it is usually called in the power economy of a central electric station.

From Table No. 6 one can see the values of the named factors for the milling industry and for all industry of the USSR.

It is also evident from it that, although the value of these factors for the milling industry is higher than for all industry of the USSR, in comparison with the utilization factors of electric motors in foreign mills they are very low, since Engineer Bell gives the annual utilization factor of electric motors in mills of the U.S.A. as, on average, 80%, which exceeds our 17.5% by more than 4.5 times.

Table No. 6.

Utilization coefficients of power apparatus, in %.

	For the milling industry	For all industry of the USSR
A) Operating primary motors.
Intensive coeff. *)	87.7	74.5
Extensive coeff.	44.1	46.2
Integral coeff.	38.7	34.5
B) Electric generators.
Integral coeff.	10.7	24.9
C) Electric motors.
Integral coeff.	17.5	16.4

Such a small utilization among us of the electric motors installed in the milling industry is apparently explained by the fact that electric motors are installed among us chiefly for auxiliary purposes, for machines that operate for an insignificant part of the time.

It is clear that such a small, irrational utilization of electric motors must be eliminated.

) 104, *) pp. 108 and 184, table 3-A.

Chapter II

Technical Principles of the Electrification of Mills

In considering the technical principles of the electrification of mills, two basic questions stand out here first of all, namely: 1) the energy consumption of mills, and 2) the transmission of energy within a mill by electricity.

The energy consumption of mills is, in general, one of the ordinary questions of the flour-milling industry, since the cost of energy constitutes one of the most important component parts of the cost of milling. It is therefore understandable that, in carrying out the electrification of mills, this question is one of the principal ones.

Bearing this in mind, below we assign this question its proper place, citing various data from foreign and Russian literature and from our own experience.

In considering the energy consumption of flour mills, it is necessary to identify clearly two main questions: 1) the total energy requirement, and 2) the distribution of energy among the separate parts and machines of the mill.

In addition, it is clear that individual types of mills also have different energy consumption.

Taking all this into account, we proceed with the further exposition.

Part A

Energy Consumption by Various Types of Mills and Its Distribution

General characteristics of the energy consumption of flour mills. 1) Energy consumption of ordinary rural s.-kh. mills with one-break grinding. 2) Energy consumption at mills for low-grade milling (seyanka). Energy consumption of commercial mills—high-grade milling (large-capacity), etc.

Energy consumption and its dependence on various factors according to data from various authors. Average energy consumption by high-grade milling mills and its distribution. Diagrams. Power required when starting the mill.

General Characteristics of the Energy Consumption of Flour Mills

We have already noted above the significance of this question for the flour-milling industry in general and for the electrification of mills in particular.

Here, however, we must once again note that, despite the importance of this question for the flour-milling industry, it has not yet been worked out with sufficient completeness: signif—

study of the individual factors affecting energy consumption in milling has still not been sufficiently clarified, which undoubtedly explains a certain diversity in the data of various authors, standards, etc., which we cite below.

One of the principal factors influencing energy consumption in milling is the type of grinding, which is usually connected with the type of mill; in view of this, below we consider this question separately for the three principal types of mills, namely: 1) agricultural mills with simple break grinding, 2) agricultural mills with bolting grinding, and 3) commercial mills with high-grade grinding (i.e., groat mills), etc.

Besides the type of mill and the kind of grinding, energy consumption depends on the size of the mill, its general arrangement and equipment and the condition of the equipment of the given mill, on the kind, quality, and condition*) of the product being processed, on the kind and grades, the quantity and their ratio, of the product being produced, etc.; and, of course, it varies even for one and the same mill depending on changes in these factors.

And although below we attempt to give average data on energy consumption for milling, it is clear that the figures we cite must be regarded as average guide figures for average conditions in the USSR.

In order to make it more convenient to compare the various data, below we everywhere give the specific energy consumption, by which we mean the energy consumption per 1 ton (1000 kg) of the daily (24-hour) capacity of the mill.

1. Energy consumption by ordinary break-type agricultural mills.

So-called break-type agricultural mills usually grind the grain produced by peasants into plain flour. This grinding is usually performed on millstones, without any preliminary cleaning of the grain.

The capacity of such mills is usually, with 2–3 runs, from 12 to 25 tons (800–1500 poods) per day, reaching in rare cases 40–50 tons.

According to Wiebe, 1 actual horsepower grinds in 1 hour: \(N_0\).

Product	Ground in 1 hour	\(N_0\)
Wheat	26.2 kg	1.59
Rye	25.7 kg	1.62

According to Baumgartner:

Product	Ground in 1 hour	\(N_0\)
Wheat	29.8 kg	1.40
Rye	22.8 kg	1.83
Raw rye	19.6 kg	2.12

Depending on the coarseness of the products produced, the Americans distinguish:

No.	Product	Output of 1 actual hp	\(N_0\)
1)	Flour (Meal)	20.5–27.3 kg in 1 hr	1.53–2.04
2)	Coarse flour (Corn. Meal)	49.0 kg	0.84
3)	Feed flour (Feed)	98.0 kg	0.43

*) Moisture content of the product being processed has an especially great effect here.

According to the summary data given below, compiled on the basis of the design of the Joint-Stock Company Soyuzkhleb, the specific energy consumption in milling at mills depends chiefly on the moisture content of the grain.

The energy consumption for simple milling at large mills with grinding on roller mills, according to this instruction, is as follows.

Specific energy consumption \(N_0\) for simple milling according to the “Soyuzkhleb” instruction (see below), with grain moisture content of

Grain	14%	16%	18%
For rye	\(N_0 = 1.35\)	1.55	1.93
“ wheat	\(N_0 = 1.10\)	1.27	1.40
“ barley	\(N_0 = 1.85\)	1.90	2.64
“ oats	\(N_0 = 2.15\)	2.47	3.06
“ buckwheat	\(N_0 = 1.2\)	1.38	1.72
“ maize	\(N_0 = 1.8\)	2.07	2.28

From this it is seen how the specific energy consumption \(N_0\) for simple milling varies depending on the type of grain being ground and its moisture content, ranging within

\[ N_0 = 1.1 \text{ to } 3.06. \]

Undoubtedly, the overall capacity of the mill is also of importance here. At small agricultural mills the specific energy consumption will be greater; at large mills, less.

According to the author’s numerous observations and experiments, when grinding on millstones various grains of average quality and average dryness (wheat, rye, and more rarely barley, oats, and buckwheat) into flour of average quality by simple flat-sifting milling at agricultural flat-sifting mills, with a daily capacity of 12–25 tons (without applying grain cleaning), it may be considered that 1 effective horsepower grinds 24.57 kg (1.5 poods) per hour, or that the specific energy consumption is \(N_0 = 1.7\) effective horsepower per 1 ton of daily mill capacity.

It is clear that with dry grain or coarse milling the output per 1 h.p. increases, and conversely—with very damp grain it falls considerably.

The author believes that the above-mentioned specific energy consumption \(N_0 = 1.7\), or the output of 1 effective h.p. per hour of 24.57 kg, may be adopted as an average value when designing the electrification of flat-sifting agricultural mills.

Below, in Chapter VI on the electrification of agricultural mills, the author gives a number of further data on the energy required, productivity, number of revolutions of millstones, and so forth, by which he recommends that the reader be guided when designing the electrification of agricultural mills and selecting the power of electric motors.

Sometimes, at agricultural flat-sifting mills, scourers are also installed, with preliminary cleaning of the grain and grinding it into scoured flour. In these cases the specific energy consumption will, undoubtedly,

is undoubtedly somewhat greater than for simple milling and may be adopted on average.

For rye . . . . . \(N_0 = 2.00\)
For wheat . . . \(N_0 = 1.55\)

When designing commercial mills for simple and break milling with large capacity (50–100 tons per day), in determining the required power one may be guided by the data of the Soyuzkhleb instructions given below*), selecting the power depending on the kind of grain being ground and its moisture content. In this, 16% may be taken as the average moisture content; when processing different kinds of grain, the corresponding change in power or capacity should be allowed for according to the data of the instructions mentioned.

2) Energy consumption at mills for sifted milling (sifting mills) ).

A type of agricultural mill, the so-called “sifting mill,” for grinding locally delivered peasant wheat grain into sifted flour, is fairly widespread in the USSR.

Here grain cleaning is already obligatorily used (trieur, scourer). Grinding is most often carried out on two systems of rollers, with the bran being ground on millstones, and the flour sifted on a sieve to obtain 1–3 grades of sifted flour. The daily capacity of such mills is usually about 11–15 tons.

It is clear that, owing to a somewhat more complex arrangement than that of mills of the 1st type, the energy consumption here per unit of grinding is somewhat greater.

According to our experiments, 1 horsepower in 1 hour grinds here on average 16.38 kg of grain (1 pood), or for 1 ton of grain ground per day the specific energy consumption required here is \(N_0 = 2.54\) h.p.

This energy consumption includes the requirement for driving the hoisting devices, grain-cleaning machines, and all working machines and mechanisms of the mill (electric lighting not included). This specific consumption may be taken as the basis in selecting the power of the electric motor.

The consumption given, as already stated, is an average one. With changes in the quality of the wheat and its moisture content it changes.

The energy consumption for producing sifted milling of rye and wheat in considerable quantities at commercial mills of the USSR may be determined according to the data of the aforementioned and fully reproduced below instructions of “Soyuzkhleb.”

Specific energy consumption (h.p. per 1 ton daily capacity) for producing sifted milling according to the Soyuzkhleb instructions for 1923.

Kind of grain	Grain moisture 14%	Grain moisture 16%	Grain moisture 18%
Rye	\(N_0 = 2.45\)	2.82	3.50
Wheat	\(N_0 = 2.10\)	2.22	2.66

) See p. 26.
*) See also Chapter VI, electrification of agricultural mills.

At an average moisture content of wheat grain of 16%, the specific consumption here is \(N_0 = 2.25\), i.e., somewhat lower than the value we cited, \(N_0 = 2.54\), for agricultural mills of sifted grinding, which is explained by the greater productivity of commercial mills.

3) Energy consumption by commercial mills of high-grade grinding (middlings) and others

Middlings mills, being the most complex of all three types, consume the greatest amount of energy per unit of processed grain.

Here a fairly complex cleaning of the grain is employed; grinding is usually conducted according to a fairly complex scheme; repeated reduction, sifting, cleaning, sorting, and transfer of products are used, which also consumes a considerable amount of energy.

As was already indicated above, energy consumption depends on many factors and is subject to fluctuations, which explains a certain diversity in the data we cite below.

We consider it necessary, however, to present here a number of data from foreign and Russian literature and practical data from operating mills and then, after analyzing this material and taking into account our own experience, to offer the reader our general conclusions, which may serve as a basis in determining the power of electric motors and in the electrification of mills.

According to F. Kettenbach*) the energy consumption of commercial mills per unit of their output is greater for small mills.

To Tables No. 7 and No. 8, based on F. Kettenbach’s data on the energy consumption of German mills of various capacities for high-grade wheat and rye grinding, we have also added \(N_0\), the specific energy consumption.

It is evident from them that for mills of high-grade wheat grinding \(N_0 = 2.6\) to \(3.3\), and for rye mills \(N_0 = 2.9\)—\(4.5\), i.e., somewhat greater for rye-grinding mills.

Table No. 7.

Energy consumption by mills of high-grade grinding for wheat
(Germany), according to F. Kettenbach.

Output, in tons per 24 hours	20	30	40	50	60	80	100	120	150	200
Energy consumption, hp	from 60 to 65	from 90 to 95	from 120 to 150	from 145 to 150	from 175 to 180	from 220 to 240	from 270 to 300	from 320 to 340	from 400 to 425	from 520 to 560
Energy consumption per 1 ton of daily output	3.3	3.2	3.0	2.9	3.0	2.0	2.8	2.8	2.7	2.6

*) F. Kattenbach, Müllerei & Mühlenbau, 1922.

Table No. 8.

Energy consumption of automatic rye-grinding mills
(Germany) according to F. Kettenbach.

Production, in tons in 24 hours	10	20	30	40	50	60	80	100	150	200
Energy consumption in h.p.	45	from 75 to 80	from 105 to 110	from 140 to 150	from 170 to 175	from 200 to 210	from 250 to 260	from 300 to 320	from 450 to 475	from 550 to 600
Energy consumption per 1 ton of daily output	4.5	4.0	3.7	3.7	3.5	3.5	3.3	3.2	3.0	2.9

As regards the distribution of energy in the mill, it is evident from the following:

The distribution of energy according to Kettenbach is given in Table No. 9; there too are given interesting data on the expenditure for idling of the separate departments of the mill.

Table No. 9.

Distribution of energy in the mill according to F. Kettenbach.

No.	Department	Work	Idle running
1)	Grain-cleaning department	22%	13%
2)	Break rolls (6 systems)	20%	14%
3)	Grinding and reduction (10–12 pairs of rolls)	25%	8%
4)	Sifting on plansifters and reels (sifting on reels 6%)	16%	9%
5)	Fans	6%	6%
6)	Transmissions	6%	6%
7)	Elevators and screws	5%	4%
	Total	100%	50%

The total energy consumption for idle running is 50% only with well-arranged transmissions; with poor transmissions the consumption rises to 55–60%.

The distribution of energy among the individual break systems (with 6) is as follows:

Break	Energy consumption
1st break	2.3%
2nd break	4.8%
3rd break	4.0%
4th break	4.0%
5th break	3.4%
6th break	1.5%
Total	20%

Energy consumption is not proportional to the length of the rolls. Kettenbach also gives interesting data to the effect that machines of insufficient dimensions, when overloaded, consume 20–25% more energy than normally loaded machines, and that by a corresponding, timely reconstruction of the mill it is possible to save in energy consumption, to obtain a product of better quality, and to have less wear of the machines than under overload.

The energy consumption of individual machines, in particular of rollers, varies depending on the length and diameter of the rollers, the speed, the kind and quantity of the product being ground, etc.

On average, the following data may be given.

Table No. 10.

Energy consumption by roller mills according to F. Kettenbach.

	500	600	750	1000	1250	1500
1) Length of shafts in mm with roller diameter 220–250 mm	500	600	750	1000	1250	1500
2) Average energy consumption of grooved rollers, hp	2.7	3.3	4.0	5.0	6.0	7.5
3) Rollers per smooth horsepower	3.3	3.5	4.5	5.5	—	—
4) Reduction rollers, hp	2.7	3.3	4.0	5.0	—	—

A millstone for grinding bran, with a diameter of 125–1300 mm, requires 7–8 horsepower.
A bolter 3–4 m long—0.6–0.7 hp.
A centrifugal bolter 2.5–3.0 m long and 780–800 mm in diameter, 0.8–0.9; a double middlings purifier, about 1.3–1.5 hp.

In general, it may be considered that 1 horsepower in 1 hour grinds, in rye mills, 10–11 kg (or 3.95 to 4.15 hp per 1 ton of daily output), and in wheat mills—13–16 kg (or from 2.62 to 3.12 hp per 1 ton of daily output).

The energy consumption of high-grinding mills, according to data from another well-known German author, Baumgartner*) varies depending on the kind of grinding, the kind of grain, its condition, etc.

With high grinding (Hochmüllerei), in small mills, for grinding 1 ton in 24 hours, \(N_0 = 5.15\) hp is required, and in large mills \(N_0 = 4.3\) hp; here the energy expenditures for lighting are not included.

Table No. 11.

Energy consumption of high-grinding wheat mills according to Baumgartner.

	5	10	15	20	25	50
Mill output in 24 h, tons	5	10	15	20	25	50
Number of effective horsepower	26	51	72	90	110	215
Per 1 ton of daily output	5.2	5.1	4.8	4.5	4.4	4.3

For rye-grinding mills Baumgartner gives the output of 1 hp in 1 hour as 10 kg, or \(N_0 = 4.15\) hp per 1 ton of daily output.

Baumgartner gives the following distribution of energy in mills with an output of 35 tons in 24 hours (6 break systems)

) Baumgartner, p. 634, Handbuch des Mühlenbanes*.

with an energy consumption of 3.55—3.60 h.p. per 1 ton of daily capacity:

Department	Share
Break rolls	21.0%
Reduction rolls	27.2%
Sifting	17.3%
Fans	5.4%
Transmissions	4.9%
Elevators	4.2%
And the grain-cleaning department	20.0%
Total	100%

For the calculation of a mill with a capacity of 48 tons per day, Baumgartner (p. 638) assumes 1 h.p. per hour per 14.0 kg (3.14 h.p. per 1 ton of daily capacity); with 23 hours of operation, 148.57 PS ≈ 150 PS are required.

Americans consider that, under continuous operation, the energy consumption of a gradual-reduction mill depends on its daily capacity and amounts on average to about 0.33 daily h.p. per 1 barrel (88.9 kg) of the mill’s daily flour output. Since Americans reckon the daily capacity of mills in barrels of flour and not in grain, in order to convert to the capacity, customary with us and in Europe, in tons of grain, it is necessary to make a recalculation according to the nature of the grain and the flour yields.*

Taking the average quality of American wheat as 60 lb per bushel, or 78 kg per hectoliter, and the average flour yield as 77%, for converting the daily capacity of mills from American barrels of flour to 1 ton of grain it is necessary to multiply the barrels by the ratio

\[ \frac{88.9}{100 \cdot 0.77} = 0.1155 \]

or \(t = 0.1155\,B\).

To obtain the specific consumption \(N_0\) of horsepower per 1 ton of grain, it is necessary to divide the specific consumption \(Nb\) of horsepower per 1 barrel of flour by 0.1155, or

\[ N_0 = \frac{Nb}{0.1155} \]

Thus the average power consumption per 1 ton of grain processed in high-grade milling mills, according to American data, will be

\[ N_0 = \frac{Nb}{0.115} = \frac{0.33}{0.1155} = 2.86 \text{ daily h.p.} \]

At the same time Americans consider that the principal energy consumption (about 70%) goes to setting in motion the reduction rolls, sifters, fans, dust collectors, and elevators (\(N_0 = 2.00\) per 1 ton (24 hours)); 11% to 16% of the total power is consumed by the grain-cleaning department (or \(N_0 = 0.315—0.457\) daily h.p. for grinding grain).

The remaining 14—19% of the power is consumed by auxiliary devices.

According to M. D. Bell, in old American mills 1 h.p. grinds 2.5—3.0 barrels of flour per day (0.33—0.40 daily h.p.

* According to G. C. Meyer Eng for the Kansas City Power & Light Co.
** For more detail on this, see at the end of the book in the section of general data and tables.

per 1 barrel), which will correspond to \(N_0 = 2.86\) to \(3.46\) h.p. per 1 ton of daily grain capacity; in modern electrified mills the energy consumption is from 6.0 to 7.5 kWh per 1 barrel of daily output (flour), or from 52.0 to 65.0 kWh per 1 ton of daily mill capacity (grain).

If we assume that the electric-energy meter is installed in the mill, and that the efficiency of the electric motor is \(\eta = 9.92\) and the transmission through wires in the mill is \(\eta = 0.96\), i.e. the overall efficiency is

\[ \eta = \eta_1 \times \eta_2 = 0.92 \times 0.96 = 0.88, \]

then the actual consumption of mechanical energy per 1 ton of daily mill capacity (grain) will be

\[ N_0 = \frac{52.0 \times 0.88}{24} = 1.91 \text{ kW, to} \]

\[ N_0 = \frac{65.0 \times 0.88}{24} = 2.39 \text{ kW.} \]

or \(N_0 = 2.6\) to \(3.25\) h.p.

The well-known American professor Dedrick*) points out that energy consumption depends on the type of transmissions used.

Table 12.

Energy consumption of a high-grade wheat mill in America, depending on the type of transmissions.

Type of transmission	Consumption per American barrel (89 kg), daily output, h.p.	Consumption per 1 ton daily output, h.p. \(N_0\)	%% ratio
1. Ordinary bearings . . .	0.4	3.46	112.5%
2. Ring-oiling bearings . .	0.36	3.12	100.0%
3. Ball bearings . . .	0.26	2.25	73.0%

From this it is evident how greatly energy consumption is reduced when ball bearings are used in all machines and transmissions.

Prt. Dedrick (P 309) determines the general calculation of energy consumption in the following manner:

Energy consumption by high-grade mills

\[ C = \frac{\pi D \times n \times L}{f \cdot b}, \quad J = \frac{L}{C} \quad N = C \times P \]

where

\(C\)—the mill output in 24 hours, in barrels of flour (at 89 kg).

\(D\)—diameter of the rolls in dm.

\(n\)—number of revolutions of the fast roll.

*) Pr. Dedrick Practical Milling.

\(\pi\) — 3.14.
\(L\) — total length, size of the roll gap of all rollers, in dm.
\(f\) — constant = 109
\(b\) — 196 (number of English pounds in 1 barrel)
\(P\) — number of horsepower per 1 barrel of mill output in 24 hours.

\[ \begin{array}{ll} 0.4 & \text{with plain bearings} \\ 0.36 & \text{with ring lubrication} \\ 0.26 & \text{with ball bearings} \end{array} \]

\(N\) — total energy consumption at the mill in horsepower, according to Dedrick.

Example: A mill has 15 four-roller stands \(9'' \times 30'' = 900''\); the number of revolutions of the fast roll is \(n = 450\) revolutions per minute; then

\[ \frac{\pi D \times n \times L}{f \cdot b} = \frac{\pi \cdot 9 \cdot 450 \times 900}{109 \times 196} = 540 \text{ barrels} \]

or

\[ J = \frac{L}{C} = \frac{900}{540} = 1.666 \text{ dm/1 barrel.} \]

Energy consumption.

\[ \begin{aligned} N = C \times P &= 540 \times 0.40 = 216 \text{ hp, with simple transmission} \\ &= 540 \times 0.36 = 183.6 \quad \text{” with ring lubrication} \\ &= 540 \times 0.26 = 130.4 \quad \text{” with ball bearings.} \end{aligned} \]

As for the distribution of energy in American mills, according to Dedrick it is as follows:

Table No. 13.

Distribution of energy in a medium-capacity mill in the U.S.A., according to Dedrick.

No.	Item	Share
1)	Grain cleaning, including receiving	16%
2)	Roller stands	40%
3)	Sifting and bolting machines	14%
4)	Auxiliary machines (bran finishers, exhausters, etc.)	13%
5)	Bucket elevators, screws, belts, transmissions	17%
	Total	100%

According to the data of engineer E. A. Hall, head of the milling-machinery department of the largest milling-machinery plant in America, Allis-Chalmers Manufacturing Co., the total energy consumption required for mills with an output, for example, of 3500 barrels (about 310 tons) in 24 hours will be approximately 0.4 double hp per barrel (\(N_0 = 3.46\) per 1 ton). This figure per barrel must, however, be increased by 10% for mills with an output of 100 barrels (9 tons) or less per day.

Energy consumption in mills varies within considerable limits depending on the quality of the wheat and the fineness of grinding. Damp and hard wheat and fine grinding require greater expenditure of energy. Hard varieties of spring wheat require more energy than soft winter wheat.

The energy consumption by individual machines at the American mill is shown in Table No. 14.

Table No. 14.

Energy consumption by individual machines of high-grinding wheat mills in America, according to Eng. Hall

I. Grinding department.

No.	Name, type, and principal dimensions of machines	Number of machines	Horsepower: each machine	Horsepower: total
1	10″ × 42″ rolls, type AA, corrugated	19	17	327
2	10 × 36 rolls, old type AA, smooth	20	20	400
3	80″ × 70 vibrating circular vertical sieves	12	3	36
4	8 ft × 32″ centrifugal reels	20	4	80
5	8 ft × 32″ round reels	4	3	12
6	7 ft × 30″ scalpers	22	2.5	55
7	7 ft × 32″ same	10	2.0	20
8	Aspirators for scalpers 7 × 40	5	0.5	2.5
9	8 ft × 32 round flour reels	4	3.0	12.0
10	No. 7 vertical brush machines for bran	6	8.0	48.0
11	Double fans, 70 dm	2	27.0	54.0
12	Same, 55 “	2	15.0	30.0
13	Single fans, 40 dm	1	8.5	8.5
14	Elevators	53	1.0	53.0
14	Dust collectors	25	0.33	9.0
	Total	77	2%	1144

II. Grain-cleaning department.

No.	Name, type, and principal dimensions of machines	Number of machines	Horsepower: each machine	Horsepower: total
1	No. 4 receiving separator (double)	1	8	8.0
2	No. 5 ” ” ”	2	10	20.0
3	Mill separators No. 90	8	10	80.0

No.	Name, type, and principal dimensions of machines	Number of machines	Horsepower: each machine	Horsepower: total
4	Automatic magnetic apparatus No. 7	1	0,125	0,125
5	Automatic magnetic apparatus No. 8	1	0,125	0,125
6	Automatic magnetic apparatus No. 10	2	0,375	0,75
7	Bolter No. 82, high	1	40,0	40,0
8	Bolter No. 92, high	2	50,0	100,0
9	Star filters No. 31 for roller mills	1	0,33	0,33
10	Star filters No. 32 for roller mills	3	0,33	1,00
11	Star filters No. 33 for roller mills	4	0,33	1,33
12	Star filters No. 36 for roller mills	1	0,33	0,33
13	Star filters No. 46 for roller mills	4	0,50	2,00
14	32 in. × 8 ft. round bolting reels	2	3,0	6,0
15	30 in. mill for grinding bran	1	60,1	60,0
16	45 in. double fan	1	14,0	14,0
17	Conveyors	16	—	6,0
	Total	22,8%	—	340

And for the whole mill, 1484 horsepower. Counting from 0.33 to 0.40 h.p. per barrel, we obtain a mill capacity of 3700 to 4500 barrels (of flour) per day, or from 427 to 520 tons of grain.

The distribution of energy in this mill is shown in Table No. 15.

Table No. 15.

Distribution of energy in a mill with a capacity of about
400–500 tons in the U.S.A.

No.	Department / operation	Share
1	Grain-cleaning department, 340 h.p.	21,0%
2	Break rolls, 324 h.p.	20,0%
3	Grinding and reduction rolls, 400 h.p.	25,0%
4	Sifting, 36 + 80 + 12 + 12 + 48 = 188	12,0%
5	Winnowing machines, 55 + 20 = 75	5,0%
6	Movement of product, 53,0; elevators and screw conveyors	3,0%
7	Ventilation, 2,5 + 54 + 30 + 8,5 + 9,0 = 104	6,0%
8	Transmissions, 90	6,0%
9	Flour packing, 28	2,0%
	Total	100,0%

In the following table are given data by A. Marsh*) on 17 American mills producing 25,914 barrels of flour per day, with a total length of the roll line of 28,656 English inches, or 1.106 inches per barrel. The energy consumption is 7,426 hp, or 3.49 barrels per 1 hp, or 0.2863 hp per 1 barrel. This amounts to only about 72% of the energy consumption usually accepted, namely 0.4 hp per barrel. The average consumption of electric energy per barrel for the 17 mills cited is 5.16 kWh.

Energy consumption by mills in America according to A. Marsh.

Mill no.	Output, barrels per day	Length of roll line, English in.	Inches of roll capacity per 1 barrel	Horsepower	Barrels per 1 hp	Horsepower per 1 barrel	kWh per 1 barrel
1	950	1068	1.124	293	3.25	0.308	5.51
2	1050	1152	1.097	306	3.43	0.291	5.22
3	1050	1212	1.059	315	3.34	0.300	5.36
4	1158	1224	1.057	319	3.63	0.275	4.90
5	1134	1224	1.079	301	3.76	0.265	4.75
6	1200	1656	1.380	408	2.94	0.340	6.10
7	1224	1656	1.353	393	3.21	0.321	5.75
8	1248	1656	1.327	377	3.31	0.302	5.41
9	1500	1692	1.126	384	3.90	0.256	4.59
10	1600	1896	1.122	436	3.66	0.272	4.88
11	1500	1800	1.200	415	3.61	0.277	4.96
12	1800	1800	1.000	463	3.88	0.257	4.61
13	1700	1956	1.151	489	3.48	0.288	5.14
14	2000	1884	0.942	578	2.46	0.289	5.18
15	2000	1884	0.942	558	3.59	0.279	4.99
16	2000	1884	0.942	537	3.72	0.268	4.81
17	2800	3012	1.097	854	3.27	0.308	5.46
Total	25914	28655	1.106	7426	3.49	0.2865	5.15

According to Kuprits**), Americans reckon 0.3 hp per 1 barrel of daily output for large mills, and 0.4 hp for small mills, or \(N_0 = 2.6\) to 3.47. The mills: Russel Milling

) See A. Marsh, Flour Mill Power, National Miller, 1929, p. 20.
) Kuprits. Rationalization of Flour-Milling Production*, p. 182.

Thus, in Buffalo, with 68 roller mills and 7 bran-finishing machines, 370 tons per day, with 30% hard wheat, consumed 1,100 h.p., or 2.87 daily h.p. per 1 ton of daily output. The Acme Evans mill, with an output of 246.6 tons, working on medium wheats, consumed 610 h.p., or 2.47 daily h.p. per 1 ton.

According to Kuprits, the Americans reckon energy consumption (p. 185) from 50 to 60 kWh per 1 ton of grain, or

\[ \frac{50}{24}\times 1.36 = 2.82\ \text{daily h.p. to}\ \frac{60}{24}\times 1.36 = 3.40\ \text{daily h.p.} \]

per 1 ton of daily output.

The distribution of energy in American mills is given in Table No. 18.

Table No. 18.

Distribution of energy in mills with an output of 200–700 tons per day in the U.S.A. (Kuprits, p. 188).

No.	Department	Share
1)	Receiving grain into silos	5%
2)	Cleaning departments	12%
3)	Roller mills	40%
4)	Sifters and winnowers	14%
5)	Aspiration	13%
6)	Bran-finishing apparatus	3%
7)	Self-discharging devices and transmissions	13%
	Total	100%

Energy consumption by commercial mills in the USSR.

We shall now present a number of data on the energy consumption of commercial mills (high milling, etc.) in the USSR.

Prof. Kozmin*) (see Table 17) gives the following energy consumption for mills in the USSR.

Table No. 17.

Energy consumption by mills in the USSR according to Prof. Kozmin.

No.	Type of milling	Number of horsepower per 100 tons of daily output	\(N_0\)
1	Once-through	140	1.4
2	Simple milling	165	1.65
3	Dehulled	183	1.83
4	Sifted	214	2.14
5	Bolted	244	2.44
6	Peklevanny	305	3.05
7	High wheat	336	3.36

) Prof. P. A. Kozmin, Flour-Milling Business*, pp. 427–28.

From the report of the Trostyanets estate, b. Koenig*) it is seen that, with a daily output of the middlings mill of 67 tons (4,000 poods) of grain, the energy consumption is expressed as 195.5 effective horsepower, or 2.92 e.h.p. per 1 ton of daily output.

In this case:

at idle running	114.9 h.p.	58.8%
useful work	80.5 h.p.	41.2%
		100%

Of this useful work:

for the grain-cleaning department	18.1 e.h.p.	22.47%
for the grinding department and offal department	62.4 e.h.p.	77.53%
	80.5 e.h.p.	100%

Engineer A. M. Borinsky,**) who determined the energy expenditure, gives the following data (see Table No. 18).

Table No. 18.

Energy consumption by high-grinding mills according to the experiments of Engineer Borinsky.

Nos.	Description of items	Mill No. 1	Mill No. 2
1	Daily output	106 tn. (6500 p.)	74 tn. (4500 p.)
2	Engine	Diesel 500 e.h.p.	Paramash. 300 ind. e.h.p.
3	Working mechanisms: 1) Roller mills, total length	20 pcs. four-roll	13 pcs. four-roll
	a) grooved	20 m. (800″)	9.2 m. (388″)
	b) smooth	20.6 (824″)	14.45 m. (578″)
	2) Millstones	2 sets, 32″ each	1 millstone 1100 mm
4	Full load	512.4 e.h.p.	264.5 e.h.p.
5	Load of rollers: a) break	34%	—
	b) smooth	24%	—
6	Full load of rollers and millstones	59%	67.5%
7	Specific energy consumption	4.85	3.56

The test of the mill of the Stalin District Flour-Milling Trust in Yasinovataya, carried out by order of Melstroy, gave the following results.

With a daily output of the mill of 100 tn. (6,160 p.) with production of graded middlings grinding, the required power was determined as 288.47 ind. e.h.p., which, at a coefficient of useful—

*) Report of the Trostyanets estate, b. Koenig.
**) Eng. A. M. Borinsky, Sov. Muk. i Khlebopechenie, 1928, No. 5.

…of the steam engine, 84.5%, gives 243.0 effective h.p., or \(N_\phi = 2.43\) effective h.p. per 1 ton of daily capacity.

From the experiments it turned out that, for the idle running of the mill and steam engine, 140.4 indicated h.p. (118.63 effective h.p.) were expended, or

\[ \frac{140.4}{288.47}=48.65\% \]

If, however, 45 indicated h.p. are excluded for the idle running of the steam engine, then for the idle running of the mill itself there were expended

\[ \frac{140.4-45.0}{288.47-45.0}=\frac{95.4}{243.47}=39.17\% \]

The scouring department during operation consumed 39.0 indicated h.p., or 13.6% of the power.

Table No. 19 gives data on the energy consumption by the individual parts of the mill.

Table No. 19.

Data on the energy consumption of the grist mill at Yasinovataya
at idle running.

Idle running	Indicated h.p.	%	Of total power 288.47 effective h.p.	Of the power expended directly by the mill: \(288.47-45.0=243.47\)
1) Steam engine (with dynamo at idle)	45.0	28.4	15.59%	—
2) Mill transmissions	25.8	19.4	8.94	10.59
3) Scouring department	15.4	10.9	5.34	6.32
4) Grinding department	54.2	38.7	18.78	22.26
Total	140.4	100	48.65	39.17

Specific energy consumption (horsepower per 1 ton of daily capacity) for different grindings and the conversion coefficients of different grindings to a standard grinding (rye meal) according to the data of the Soyuzkhleb instructions.

By the Joint-Stock Company “Soyuzkhleb,” on September 12, 1928, special instructions and norms were issued for the power installations of mills.* In these instructions interesting data are given on the specific energy consumption for different grindings and on the change of this specific consumption as a function of changes in the moisture content of the grain.

* See Instructions and Norms for the Power Installations of Mills, Joint-Stock Company “Soyuzkhleb,” 1928.

As can be seen from the table given below, the specific consumption varies, according to this instruction, depending on the type of milling, amounting to:

Simple milling of wheat — 1.10 hp per 1 ton of daily output.
rye — 1.35
Sifted milling of wheat — 2.10
High-grade milling of wheat — 3.05

In the second column are given the coefficients for conversion to standard milling, which is here taken to mean wholemeal rye milling.

Table of specific energy consumption for different millings and coefficients for conversion to standard milling (wholemeal rye), according to the instruction of “Soyuzkhleb,” 1928

Type of grain	Type of milling	Specific energy consumption, hp per 1 ton daily output	Coeff. for conversion to standard milling	Note
Rye	Simple	1.35	0.89	When processing rye into wholemeal flour on a high-grade mill, one may take 1.98 hp, coefficient 1.3; and when processing wheat into wholemeal flour, 1.60 hp and coefficient 1.05.
Rye	Wholemeal	1.52	1.00	When processing rye into wholemeal flour on a high-grade mill, one may take 1.98 hp, coefficient 1.3; and when processing wheat into wholemeal flour, 1.60 hp and coefficient 1.05.
Rye	Hulled	1.70	1.11	When processing rye into wholemeal flour on a high-grade mill, one may take 1.98 hp, coefficient 1.3; and when processing wheat into wholemeal flour, 1.60 hp and coefficient 1.05.
Rye	Tailings	2.00	1.31	When processing rye into wholemeal flour on a high-grade mill, one may take 1.98 hp, coefficient 1.3; and when processing wheat into wholemeal flour, 1.60 hp and coefficient 1.05.
Rye	Sifted	2.45	1.61	When processing rye into wholemeal flour on a high-grade mill, one may take 1.98 hp, coefficient 1.3; and when processing wheat into wholemeal flour, 1.60 hp and coefficient 1.05.
Rye	Peklevan	2.75	1.81	When processing rye into wholemeal flour on a high-grade mill, one may take 1.98 hp, coefficient 1.3; and when processing wheat into wholemeal flour, 1.60 hp and coefficient 1.05.
Wheat	Simple	1.10	0.72	Henceforth, until the matter is clarified, it is accepted that in the case of processing wheat with an admixture of rye, maize, barley, etc., into high-grade flour, the power consumption per ton and the conversion coefficient increase in inverse proportion to the decrease in processing.
Wheat	Wholemeal	1.25	0.82	Henceforth, until the matter is clarified, it is accepted that in the case of processing wheat with an admixture of rye, maize, barley, etc., into high-grade flour, the power consumption per ton and the conversion coefficient increase in inverse proportion to the decrease in processing.
Wheat	Tailings	1.65	1.08	Henceforth, until the matter is clarified, it is accepted that in the case of processing wheat with an admixture of rye, maize, barley, etc., into high-grade flour, the power consumption per ton and the conversion coefficient increase in inverse proportion to the decrease in processing.
Wheat	Sifted	2.10	1.38	Henceforth, until the matter is clarified, it is accepted that in the case of processing wheat with an admixture of rye, maize, barley, etc., into high-grade flour, the power consumption per ton and the conversion coefficient increase in inverse proportion to the decrease in processing.
Wheat	High-grade	3.05	2.00	Henceforth, until the matter is clarified, it is accepted that in the case of processing wheat with an admixture of rye, maize, barley, etc., into high-grade flour, the power consumption per ton and the conversion coefficient increase in inverse proportion to the decrease in processing.
Barley	Into flour	1.85	1.22	Henceforth, until the matter is clarified, it is accepted that in the case of processing wheat with an admixture of rye, maize, barley, etc., into high-grade flour, the power consumption per ton and the conversion coefficient increase in inverse proportion to the decrease in processing.
Oats	Into flour	2.15	1.41	Henceforth, until the matter is clarified, it is accepted that in the case of processing wheat with an admixture of rye, maize, barley, etc., into high-grade flour, the power consumption per ton and the conversion coefficient increase in inverse proportion to the decrease in processing.
Buckwheat	Into flour	1.20	0.71	Henceforth, until the matter is clarified, it is accepted that in the case of processing wheat with an admixture of rye, maize, barley, etc., into high-grade flour, the power consumption per ton and the conversion coefficient increase in inverse proportion to the decrease in processing.
Buckwheat	Into groats	1.00	0.66	Henceforth, until the matter is clarified, it is accepted that in the case of processing wheat with an admixture of rye, maize, barley, etc., into high-grade flour, the power consumption per ton and the conversion coefficient increase in inverse proportion to the decrease in processing.
Millet	Hulled millet	0.90	0.59	Henceforth, until the matter is clarified, it is accepted that in the case of processing wheat with an admixture of rye, maize, barley, etc., into high-grade flour, the power consumption per ton and the conversion coefficient increase in inverse proportion to the decrease in processing.
Millet	Crushed millet	1.25	0.82	Henceforth, until the matter is clarified, it is accepted that in the case of processing wheat with an admixture of rye, maize, barley, etc., into high-grade flour, the power consumption per ton and the conversion coefficient increase in inverse proportion to the decrease in processing.
Maize	Simple	1.80	1.18	The present figures are adopted for mills of high-grade wheat milling converted to the processing of maize. For special mills one should take 3.5 hp and coefficient 2.3.
Maize	High-grade	4.00	2.63	The present figures are adopted for mills of high-grade wheat milling converted to the processing of maize. For special mills one should take 3.5 hp and coefficient 2.3.
Maize	Into groats	1.20	0.79	The present figures are adopted for mills of high-grade wheat milling converted to the processing of maize. For special mills one should take 3.5 hp and coefficient 2.3.
Peas	Into flour	1.80	1.18	The present figures are adopted for mills of high-grade wheat milling converted to the processing of maize. For special mills one should take 3.5 hp and coefficient 2.3.

Further, in the above-mentioned Instruction of “Soyuzkhleb,” on p. 24, very interesting data are given on the coefficients of increase in the specific energy consumption when the moisture content of the grain being processed is increased. These coefficients serve as additional correction coefficients when converting to standard milling, if the grain moisture exceeds 15% for wheat and 14% for rye, buckwheat, and millet.

Table of coefficients of increase in the specific consumption of energy and fuel with an increase in grain moisture (inversely proportional to the decrease in productivity). According to the Instruction of “Soyuzkhleb,” 1928.

Moisture, %	14	14.5	15	15.5	16.0	16.5	17.0	17.5	18.0	18.5	19.0	19.5	20
KIND OF GRAIN:
Wheat	1	1	1	1.03	1.06	1.10	1.15	1.20	1.27	1.33	1.43	1.54	1.66
Rye, buckwheat, millet	1	1.03	1.06	1.10	1.15	1.20	1.27	1.33	1.43	1.54	1.70	1.88	2.22

Note: The grain moisture is taken in the receiving pit.

For greater clarity, we have plotted this increase in specific consumption with increasing moisture in the form of curves (see Fig. 1).

Fig. 1. Increase in the specific consumption of energy for grinding as a function of grain moisture.

From the table and Figure 3 it is clear that if, for example, the specific energy consumption in graded milling of wheat at a moisture content of 15% is \(N_0 = 3.05\) h.p. per 1 ton of daily output, then at 16% moisture it will increase by a factor of 1.06, at 17% by a factor of 1.15, etc.

Unfortunately, the Instruction contains no data indicating for what daily capacity of the mill the specific energy consumption is given, nor does it indicate how it changes as this capacity changes. Meanwhile, as will be shown below, the specific consumption changes considerably, decreasing as the daily capacity of the mill increases.

Assuming that the data on specific consumption in the Instruction of Soyuzkhleb are given for a mill with a daily capacity, in graded milling, of 100 tons, then, at the average moisture content of wheat grain processed in commercial mills for graded milling of 16%, according to the data of the Instruction, we obtain an average specific energy consumption for mills of this capacity of \(3.05 \times 1.06 = 3.23\) h.p., which almost completely coincides with the average data given by us below (3.2 h.p.) for mills of this capacity.

Average Energy Consumption by High-Grade Milling Mills and Its Distribution

From all the data presented above by us and other materials—some of which the scope of the present work does not permit us to include here—as well as from the data of our own experience, we arrive at the following basic conclusions concerning the energy consumption of high-grade milling mills and its distribution. It is necessary to stipulate that the data presented are average approximate figures, but we believe that they may be taken as a basis in designing the electrification of mills and in selecting electric motors for them.

1) The energy consumption of high-grade milling mills depends on many factors, among which the most important are: a) the kind, quality, and condition (chiefly moisture content) of the product being processed; b) the construction, equipment, capacity, and degree of loading of the mill, and the milling systems employed; c) the kind, grades, and qualities of the products being produced.

Thus, for example, the grinding of hard grain requires more energy than that of soft grain, as does damp grain compared with dry grain. A mill equipped according to the latest word in technology, with ball-bearing transmissions, requires less energy than a mill of ordinary construction. The greater the capacity of the mill, the lower the specific energy consumption for grinding, etc., etc.

2) The actual average specific energy consumption at high-grade milling mills in the USSR—that is, the number of effective h.p. per 1 ton of grain processed at mills in 24 hours—may be taken in accordance with the table No. 20 compiled by us. From it, and still more clearly from the diagram in Fig. 2, it is evident that the specific energy consumption decreases as the daily capacity of the mill increases.

Table No. 20.

Actual average specific consumption of high-grinding mills in the USSR.
By S. Balakshin.

Daily output of the mill, tons	Specific energy consumption, d. h.p.	Daily output of the mill, tons	Specific energy consumption, d. h.p.
10	4.20	200	3.10
30	3.85	250	3.08
50	3.60	300	3.05
100	3.20	460	3.00
150	3.15

In determining this actual specific energy consumption, we have taken into account the energy consumption solely for driving the grain-cleaning and grinding departments of an average-equipped mill. The energy consumption for the elevator and for electric lighting is not included here.

The energy consumption given by us in Table No. 20 refers to modern mills in the USSR of average arrangement (transmissions with ring lubrication) when grinding grain of average moisture content of 16%; with a change in the moisture content of the grain being processed, this consumption will change, and in determining it in this case one may use the conversion coefficients of the above-cited instruction of Soyuzkhleb (see table).

Thus, for example, if for a mill with a daily output of 200 tons, according to Table No. 20, \(N_0 = 3.10\) d. h.p. at 16% grain moisture, then with grain of 14% moisture this consumption will be

\[ N_0 = \frac{3.10}{1.06} \times 1.0 = 2.93 \text{ d. h.p.} \]

In Fig. 2 we have also given the specific energy consumption according to German data of Kettenbach, which, in our opinion, are insufficient (as averages) for our conditions and may be considered minimal, and the data of Baumgartner and American data on actual consumption by electrified mills of America (according to Bell, Dedrick).

From Fig. 2 it is evident that the actual average specific energy consumption by American high-grinding mills closely approaches our data for mills of the USSR on actual energy consumption, but is considerably reduced when ball bearings are used (see the lower line according to Dedrick).

This gives us reason to pay special attention to the use of ball-bearing transmissions in all newly constructed mills and to the gradual replacement of sta-

transmissions in existing mills in order to obtain a considerable saving of energy, and consequently also a reduction in the cost of grinding.

Fig. 2. Energy consumption per 1 ton of daily grain grinding capacity in high-grade grinding mills.

3) The average actual energy consumption directly by mills of various capacities and the power of the necessary

Table No. 21.

Average actual energy consumption and required power of electric motors for fine-grinding mills.

Average daily output of mills, tons	For USSR mills according to Valakshin: actual energy consumption, hp	For American mills according to Beli: actual consumption of all energy, hp (minimum)	For American mills according to Beli: actual consumption of all energy, hp (maximum)
10	50	—	—
30	110	—	—
50	170	—	—
100	320	260	325
150	470	390	487
200	620	520	650
250	760	650	815
300	910	780	975
400	1200	1040	1140

The power of the electric motors can readily be obtained by using Table No. 21 and the curves in Fig. 2.

These curves have been plotted by us in accordance with the data on specific energy consumption explained in detail above in the preceding paragraph (§ 2).

Moreover, these data also refer to the processing of grain with an average moisture content of 16%. If the moisture content changes, the required power will change; it can be determined by using the transition coefficients of the Soyuzkhleb instructions, as was explained in the preceding paragraph.

It should be noted that the above data on energy consumption at a fine-grinding mill refer only to the energy consumption for driving the mill itself. The energy consumption for electric lighting*) of the mill, and also for driving conveying and other devices in separate elevators attached to mills, is not included here and must be taken into account separately when calculating electrification.

4) Consumption of electrical energy.

The above data on consumption (§ 2 and Fig. 2) and on actual consumption (§ 3 and Fig. 3) of energy give the consumption of mechanical energy by mills.

To obtain the consumption of electrical energy, it is also necessary to take into account losses in the electric motor, wires, etc., depending on where the meter is installed**), i.e., also to take into account the efficiency of these individual component elements of the transmission, as well as the additional consumption of electrical energy when starting the mill.

) On the consumption of electrical energy for electric lighting of mills, see Chapter IV, electric lighting of mills.
*) For details on the transmission of energy by electricity, see Part III, Transmission of energy to mills by electricity.

Thus, if, for example, the electric-energy meter is installed at the electric motor itself that drives the mill, and the efficiency of the electric motor is \(\eta = 0.9\), then, with a specific energy consumption of a mill with a daily capacity of 100 tons at 16% moisture of \(N_0 = 3.2\) (Table 20), the consumption of electric energy in kW-hours per ton is determined from:

\[ E_0=\frac{N_0 \times 24}{1.36 \times \eta} =\frac{3.2 \times 24}{1.36 \times \eta} =62.9\ \text{kW-hours per 1 ton,} \]

where

\(N_0\) — specific energy consumption per 1 ton in h.p.
24 — number of hours in a day
1.36 — number of h.p. in 1 kilowatt
\(\eta\) — efficiency coefficient of the electric motor.

The actual consumption of electric energy will be somewhat greater, since we have not taken into account here the additional consumption of electric energy when starting up the mill, and have assumed that the mill operates continuously around the clock, with a uniform, full load; when the load changes, the specific consumption and the efficiency of the electric motor change, which in turn, of course, affects the energy consumption.

The average actual consumption of electric energy may, according to American data, be taken as from 50.0 to 65.0 kW-hours per 1 ton of daily capacity (grain) of the mill.

5) Distribution of energy.

We believe that, on the average, the following distribution may be adopted for the energy consumed by the individual operations of merchant mills (Table 22).

Table 22.

Distribution of energy in mills of high grinding, according to S. Balakshin.

	From—to %	Average %	At idle running
1) Grain-cleaning department	21.0—23.0	22.0%	12.0%
2) Break rolls	14.0—20.0	17.0%	4.0%
3) Reduction and sizing rolls	22.0—26.0	24.0%	8.0
4) Sifters (plansifters, reels)	12.0—16.0	14.0	7.0
5) Fans	5.0—7.0	6.0	5.0
6) Product conveying (elevators, augers)	3.0—7.0	5.0%	3.0
7) Ventilation	4.0—6.0	5.0%	4.0
8) Transmissions	4.0—8.0	6.0%	6.0
9) Discharge	1.0—3.0	1.0	1.0
Total	—	100%	50%
10) Service at the mill elevator with a grain reserve	7.0—13.0	10%
11) Electric lighting	6.0—10.0	8%
	—	18%

For greater clarity, we show table No. 22 in Fig. 3 in the form of a diagram. From Fig. 3 the energy consumption is clearly visible for minimum, average, and maximum values, as well as for idling.

1. Grain-cleaning department.
2. Breaking rolls.
3. Reduction rolls.
4. Sifting.
5. Veikas.
6. Product conveying.
7. Ventilation.
8. Transmissions.
9. Millstone.

In addition:

1. Elevator at the mill.
2. Electric lighting.

Legend:

• idling
• minimum working energy
• average working energy
• maximum working energy

Fig. 3. Distribution of energy in high-grinding mills.

In Fig. 4 we have shown, in the form of a diagram, the general distribution of energy in high-grinding mills.

1) Rolls, plansifters, veikas, dust collectors, elevators — 66%
2) Grain-cleaning department — 22%
3) Ventilation, transmissions, millstone — 12%

Fig. 4. General distribution of energy in high-grinding mills.

Power required when starting a mill.

It is known that when starting a mill, especially after a more or less prolonged shutdown in winter, when the lubricant in the bearings thickens, the expenditure of considerably more energy is required than after the mill has begun running and all its mechanisms have warmed up.

This question has still been investigated comparatively little; nevertheless, in the electrification of mills it is of especially great importance. Whereas steam and similar engines can develop, for a short time, torques considerably exceeding the working ones, electric motors, as a rule, do not permit too great an overload; as a result, here it is necessary to resort to the use of coupling clutches that gradually engage the working mechanisms, or to special electric motors with a high initial torque.

According to American data, the torque when starting a high-grinding mill after prolonged stoppages (for example, on rest days) usually exceeds by 200%—300% the normal torque during continuous operation of the mill.

An original device has been applied at one American mill. The main electric motor is arranged there in such a way that its stator (which is stationary during operation) can rotate and can gradually be braked by a special brake. When, after a prolonged stoppage of the mill, it is desired to start it, the stator brake is released and the electric current is switched on. The stator begins to rotate gradually and, as it is braked, sets the rotor in motion. Care is taken that the current strength, as indicated by the ammeter, does not exceed certain limits permissible for the electric motor; and when its rotor has reached the normal number of revolutions, the stator is completely stopped, the brake being secured for the entire period of operation of the mill.

In Fig. 5 the change in power when starting a mill is clearly shown, as given by A. M. Marsh*).

Fig. 5. Change in power when starting the mill.

In the first seconds, as can be seen from the diagram, double power is required—300 h.p. as against the 150 h.p. usually required for driving the mill. By the end of 5 seconds this power falls to 206 h.p.; by the 10th second, to 130 h.p.; and at 25 seconds, to 110 h.p. In other words, 110 h.p. is required here in order to rotate the mill before grain has been admitted, after which the load rises to 150 h.p.

As has already been said above, and as will be explained by us in more detail below, in order to overcome this initial resistance of mills, special electric motors are used whose initial starting torque is 2—2.5 times greater than the normal working torque.

) A. M. Marsh, “Flour Mill Power,” National Miller*, September 1929, p. 20.

CHAPTER III.

Part B.

Transmission of Energy in Mills by Electricity.

1. Direct-current motors. General principles of transmission and operating features of direct-current motors.
2. Alternating-current motors: a) general principles of transmission arrangement, efficiencies. Power. Diagrams: a) types of alternating-current motors: asynchronous, synchronous, etc. General arrangement. Characteristics and peculiarities of electric motors for flour mills and their types. Examples. Electric motors of GET plants for mills.
3. General arrangement of transmission by electricity in flour mills. Individual and group electric motors. Installation of electric motors in mills. Transmission of motion from electric motors. General basic arrangements of electric transmission in mills.

As has already been indicated above, the transmission of energy in mills by electricity—“the electrification of mills”—has recently, especially in America, been gaining ever wider and wider application.

In mills, both direct-current and alternating-current motors (synchronous and asynchronous) have found use, in view of which we shall touch briefly below upon the advantages and disadvantages of these principal types of electric motors and their peculiarities for flour mills.

1) Direct-current motors.

Direct current has, as is known, the major disadvantage that it is impossible to change its voltage by simple technical means, owing to which, in the transmission of energy, comparatively low voltages have to be used; this in turn necessitates a considerable cross-section of conductors and makes them comparatively expensive.

Therefore, direct current at the present time has found application for the transmission of energy only over comparatively very short distances and in mills almost exclusively for motors of comparatively low power (for fans, conveyor belts, etc.).

The strength of electric current is measured in amperes, and the voltage in volts.

The voltage of direct current is at present usually taken as

\[ V = 110, 220 \text{ or } 440 \text{ volts.} \]

The power of a direct-current electric motor is determined by the formula

\[ P = E \times J \times \eta \text{ watts, or } W = \frac{E \times J}{1000}\eta \text{ kilowatts.} \]

where \(P\)—power of the electric motor in watts.
\(W\)—the same, in kilowatts
\(E\)—current voltage in volts.
\(J\)—current strength in amperes.
\(\eta\)—efficiency coefficient of the electric motor.

To convert the power of an electric motor into effective horsepower, it is necessary to divide the number of watts \(P\) by 736, or to multiply \(W\)—the number of kW—by 1.36, i.e.

\[ N_e=\frac{P}{736} \]

or \(N_e=1.36W\) effective horsepower.

Example. We have a direct-current electric motor operating at the exhaust fan of a mill, which, at a current voltage \(V=220\) volts, consumes \(J=10.2\) amperes.

The efficiency coefficient is

\[ \eta=0.8. \]

Then

\[ P=E\times J\times \eta=220\times 10.2\times 0.8=1910\ \text{watts} \]

or

\[ W=1.910\ \text{kW}, \]

or

\[ N_e=1.36W=\sim 2.6\ \text{effective horsepower}. \]

Fig. 6. Housing of a direct-current electric motor.

A direct-current electric motor consists of a housing (see Fig. 6), inside which there are a number of electromagnets and the armature placed within it (Fig. 7).

The armature of direct-current electric motors always has a commutator, along which, during rotation of the armature, brushes slide, transmitting electrical energy to the electric motor.

This is a major drawback of direct-current electric motors for mills, since the brushes usually produce sparks, from which mill dust may ignite.

Fig. 7. Armature (rotor) of a direct-current electric motor.

The electrical energy entering a direct-current electric motor must, on the one hand, pass through the winding of the electromagnets, and on the other hand through the brushes and commutator and the armature winding.

Three types of connections are used (Fig. 8).

1. Shunt circuit.
2. Series (sequential).
3. Compound.

Fig. 8. Basic circuits of direct-current electric motors.

Most often a shunt winding system is used; moreover, in the wire supplying current to the electromagnets there is usually placed a rheostat (resistance), which, after the motor begins to reach its normal number of revolutions, is gradually switched out.

2) Alternating-current electric motors.

a) General principles of the transmission arrangement.

Alternating-current electric motors, owing to the convenience and economic advantages of transmitting energy by this kind of current, have found the widest application for mills.

In the electrification of a mill, energy is usually obtained from central electric stations, sometimes located at a fairly considerable distance from the mill. Almost exclusively three-phase current is used.

The general scheme for the transmission of electrical energy here is usually as follows (see Fig. 9).

Fig. 9. General scheme for the transmission of energy by alternating current.

As can be seen from the diagram in Fig. 9, the electric generator, driven at the power station by a steam turbine (or water turbine, diesel, etc.), develops three-phase current (in Fig. 9 the voltage is 2000 volts). The voltage, by means of a transformer at the power station, is raised in accordance with the transmission distance (in the figure, 10000 volts), and by means of wires the current, along the energy-transmission line (wires suspended on insulators from wooden or metal poles), is transmitted to the mill.

Here, by means of a transformer, the current voltage is reduced to the limits of safe use, and the electrical energy is supplied to the working electric motors of the mill.

The standard working current voltages adopted at present for the USSR are:

220, 380, 500; 3000 and 6000 volts.

The last two voltages, 3000 and 6000 volts, are used for the main, separately installed electric motors of the mill.

The working current voltage adopted at present in America is: \(V = 2300\) volts for the main motors of the mill, \(V = 440\) for secondary, smaller electric motors.

It is clear that in the transmission of energy by electricity, losses of it are inevitable, both in the prime mover, the generator, the transformers and the wires, and in the electric motor. These losses (and consequently also the coefficient of useful effect) vary with changes in load, as can easily be seen from the characteristics given by us in Fig. 10.

Fig. 10. Characteristics of the variation of the coeff. of useful action of the individual elements of electric transmission, depending on the variation of load.

As an example of losses in the transmission of alternating current we cite the losses in the transmission of electrical energy by water power.

The total coefficient of useful action of the whole transmission is always equal to the product of the c.u.a. of all its component parts.

Coefficient of useful action in the transmission of water energy.

1. Water turbine . . . . . . . . . . . . . . . . . $\eta_1 = 0.8—0.935$
2. Electric-current generator . . . . . . . . . . $\eta_2 = 0.92—0.94$
3. Step-up transformer . . . . . . . . . . . . . $\eta_3 = 0.96$
4. Transmission line . . . . . . . . . . . . . . $\eta_4 = 0.9$
5. Step-down transformer . . . . . . . . . . . . $\eta_5 = 0.96$
6. Electric motor . . . . . . . . . . . . . . . . $\eta_6 = 0.90—0.94$

Full coeff. of useful action:

\[ \eta = \eta_1 \times \eta_2 \times \eta_3 \times \eta_4 \times \eta_5 \times \eta_6 = 0.548—0.691 \]

It is clear that when a steam or some other engine is used, other coefficients and their efficiencies will enter in.

Counting the energy on the busbars of the power station, without transmission over a distance, the coefficient of useful action of the transmission will of course be higher,

\[ \eta = \eta_3 \times \eta_4 \times \eta_5 \times \eta_6 \]

and on the busbars in the mill still higher,

\[ \eta = \eta_5 \times \eta_6. \]

Before proceeding to the description of the principal types of alternating-current electric motors, we shall allow ourselves to give the basic formulas for alternating current.

Basic formulas for alternating current.

Number of periods of alternating current.

At the present time it is accepted:

In Europe $c = 50$ in 1 second.
In America $c = 60$ ” ” ”

If:

\[ \begin{aligned} n&\text{—number of revolutions of the generator per min.}\\ p&\text{—number of poles}\\ c&\text{—number of periods in 1 sec.,} \end{aligned} \]

then:

\[ n=\frac{120\cdot c}{p} \qquad \text{for example}\quad c=60,\quad p=20 \]

Then

\[ n=\frac{120\cdot 60}{20}=360 \text{ revolutions in 1 min.} \]

Three-phase wires may be connected either according to the star scheme (see Fig. 11), or according to the delta scheme (see Fig. 12).

Fig. 11. Star connection.

Fig. 12. Delta connection.

Power Developed by Alternating Current.

In determining the power developed by alternating current, it is also necessary to take into account the so-called \(\mathrm{Cos}\,\varphi\), or the cosine of the angle between the current intensity and the voltage.

If:

\[ \begin{aligned} P&\text{—number of watts.}\\ W&\text{—kilowatt}\\ E&\text{—current voltage in volts.}\\ J&\text{—current intensity in amperes}\\ \varphi&\text{—angle between }E\text{ and }J. \end{aligned} \]

Then the theoretical power in watts is \(P=E\cdot J\cdot \mathrm{Cos}\,\varphi\) for single-phase alternating current, \(P=2EJ\mathrm{Cos}\,\varphi\) for alternating two-phase current.

\[ P=\sqrt{3}EJ\mathrm{Cos}\,\varphi \qquad \text{”}\quad \text{three-phase.}\quad \text{”} \]

Or:

Kilowatts = kilovolt-amperes \(\mathrm{Cos}\,\varphi\)

\[ \text{kw.}=KVA\,\mathrm{Cos}\,\varphi \]

If, for example, we have electrical power of \(P=100\) kilowatts, then, with \(\mathrm{Cos}\,\varphi=0.8\), the power will be

\[ \frac{\text{kw}}{\mathrm{Cos}\,\varphi}=\frac{100}{0.8}=125 \]

kilovolt-amperes

\[ 1\ \text{kw.}=1000\ \text{watts.}\quad 1\ \text{horsepower}=736\ \text{watts.} \]

Example. A three-phase electric motor driving the mill rollers consumes \(J=50\) amperes at \(E=2300\) volts. Then the power developed by it will be:

\[ N_e=\frac{\sqrt{3}E\cdot J\cdot \mathrm{Cos}\,\varphi}{736}\times \eta \]

assuming \(\cos \varphi = 0.8\)

\[ \eta = 0.92 \]

We obtain:

\[ N_e = \frac{\sqrt{3}\times 2300 \times 50 \times 0.8}{736}\times 0.92 = 218\ \text{h.p.} \]

c) Types of alternating-current motors.
The alternating-current motors used at the present time may be divided into two main types:

1. Asynchronous*) motors (“Induction motor”), where the rotation of the rotor does not coincide with the rotation of the magnetic field, and

2. Synchronous motors (“Synchron motor”), where the rotation of the rotor almost coincides with the rotation of the magnetic field and, depending on this, the number of revolutions remains almost constant at all times.

1. Asynchronous motors.
Asynchronous motors, in turn, are divided into three principal types, namely:

a) asynchronous motors with a simple winding,
b) ” ” with a double ”
c) ” ” with a phase rotor.

Characteristics of the Principal Types of Alternating-Current Motors

For a better understanding of the special features during starting and operation of alternating-current motors, we shall give below the characteristics of their principal types.

a) Asynchronous motor with a short-circuited winding.

The rotor (armature) is a so-called squirrel cage: in the form of two copper rings \(m\) and \(n\) (see Fig. 13), connected by a series of copper bars of the winding.

These bars are made either inclined with respect to the axis of the rotor, or the number of winding sectors is made somewhat greater or smaller than in the stator, in order to avoid pulsations. The iron body of the rotor is made, to avoid Foucault currents, from separate laminations.

The winding bars are usually held in it by means of wooden wedges (see Fig. 13), etc.

Fig. 13. Diagram of an asynchronous motor with a simple winding.

*) Which in Greek means: “non-simultaneous.”

The stator winding is placed in the slots of its frame.
Fig. 14 shows the principal parts of an asynchronous three-phase electric motor with a squirrel-cage rotor.

Fig. 14. Three-phase asynchronous electric motor with a squirrel-cage rotor (principal parts).

Its advantage is that it has neither a commutator nor rings with brushes, and can be completely enclosed.

Its disadvantage, as is evident from the characteristic given below, is the small starting torque. To obtain the normal torque that occurs during operation, it is necessary to increase the current at starting by 6–7 times.

As is seen from Fig. 15, an asynchronous motor with a single winding is characterized by the following features:

1. Large current at starting.
2. Low efficiency coefficient at starting.
3. Low \(\cos \varphi\) at starting.
4. Low torque \(M\) at starting, gradually increasing.

Fig. 15. Characteristic of an asynchronous motor with a single winding.
Rotor speed in % of the speed of rotation of the magnetic field.

1. Ratio of torque

\[ \frac{M \max}{M \text{ norm}} = 2 \div 2.5 \div 3. \]

1. Slip

\[ \text{Slip} \begin{cases} 1\% & \text{in motors of } 100 \text{ h.p.},\\ 2\% & \text{” } 10,\\ \text{up to } 5\text{–}6\% & \text{” } 1\text{–}2 \text{ h.p.} \end{cases} \]

c) Asynchronous motor with double winding.

To increase the starting torque and at the same time increase \(\cos \varphi\), asynchronous motors with double winding are made. Each rotor winding is made, as in asynchronous motors with a simple winding, of a series of rods connected at the ends.

by separate rings. For the indicated increase in starting torque, the outer winding of the rotor (see Fig. 16) is made with greater ohmic resistance (nickeline, tombac, etc., are used for it) than the inner one.

Fig. 16. Diagram of the rotor of an asynchronous motor with a double winding.

In Fig. No. 17 one can clearly see the change in torque as the motor is loaded—both for the separate windings and for the total torque.

Fig. 17. Change in the torque of an asynchronous motor with a double winding.

The efficiency here is small at first, but gradually increases. \(M\) at starting is 2–2.5 times greater than in asynchronous motors with a single winding. Here the commutator is completely absent.

c) Phase-wound asynchronous motor (with slip rings).

A phase-wound asynchronous motor for three-phase current is characterized by a rotor winding consisting of three separate sections, with one set of ends of the phase windings connected together, while the other ends go to three rings of a special commutator on the rotor shaft; from its brushes wires go to the rheostat (see the diagram in Fig. 18).

Fig. 18. Diagram of a phase-wound asynchronous motor with slip rings.

When starting the motor, the greatest resistance of the rheostat is switched into the circuit, which gives the greatest torque. Then they switch to a somewhat smaller resistance, then still smaller, and when the motor has come up to speed, the rheostat is switched off, and the brushes can then even be lifted completely from the commutator.

Figure 19 shows clearly:

1. The greatest resistance of the rheostat.
2. Reduced resistance.
3. Still smaller.
4. Rheostat switched off.

The upper thick line is the gradual change in torque, which remains high throughout.

Fig. 19. Change in torque of a phase asynchronous motor.

In a phase asynchronous motor, the rotor and stator have identical windings (the difference is only in the number of turns and the thickness of the wire).

Motors of this type have no projecting poles (the air gap between the stator and rotor remains constant).

Figure 20 shows the principal parts of a phase asynchronous electric motor for three-phase current with three rings.

Fig. 20. Phase asynchronous electric motor for three-phase current with slip rings.

When, by means of a special device, the armature winding is short-circuited, it continues to operate like an ordinary short-circuited armature. Electric motors of this type are the most suitable for mills, where the work proceeds continuously, but where a considerable initial torque is required. The voltage of the current in an electric motor is not

must vary by more than \(+5\%\). When the voltage is lowered, the power drops; when it is raised, overheating of the iron in the motor occurs.

Synchronous motors.

Synchronous motors are characterized by a constant number of revolutions corresponding to the number of poles and periods.

Motors of this type have a constant magnetic field, produced by direct current passed through the winding. To obtain this, these motors usually have special exciters.

When starting, synchronous motors usually have first to be set into rotation until they acquire synchronous speed.

A feature of synchronous motors is that here, for the most part, there are salient poles (a non-uniform air gap).

The convenience of synchronous motors consists in the fact that they can be reversed into generators of electric current, in consequence of which, as already indicated above, they are sometimes used in mills by putting the rotor, for example, on the shaft of a water turbine and using it either as an electric-current generator (when it is necessary to deliver energy in the form of electricity) or as an electric motor (when there is little water and it is necessary to operate with electrical energy obtained from outside).

In general, however, owing to a number of shortcomings inherent in synchronous motors and to the advantages of asynchronous motors, the latter are used chiefly in mills.

Supersynchronous motors.

(Supersynchronmotors).

In America a number of firms are building and installing on mills so-called supersynchronous motors.

These are, properly speaking, asynchronous motors with double feed and double synchronous speed. The double feed consists in the fact that alternating current is supplied from the network to the stator and, through a slip-ring commutator, to the rotor.

A supersynchronous motor has no exciter whatever.

Its starting characteristic is analogous to that of asynchronous motors.

c) Features of electric motors for flour mills.*)

As indicated above, electric motors for mills, in addition to all ordinary qualities (high coefficient of efficiency; high power factor—\(\cos \varphi\), etc.), must possess the following three special features:

1. Have, as far as possible, a large starting torque.
2. The lowest possible number of revolutions (for direct connection with mill machines and transmissions).
3. Not be afraid of the dust of mill premises.

The absence of electric motors with these features, as Bell indicates,**) for a long time even served as an obstacle to the broad

*) See also below: electric motors for mills of the GET plants in the USSR.
**) Bell, Mechanical Engineering, 1928, p. 83.

electrification of mills in America, and only after prolonged efforts and many years of work did American electrical engineers succeed in creating electric motors satisfying the above-mentioned conditions for mills.

We shall give here a description of the types now being built.

Types of casings for three-phase-current electric motors.

Fig. 21 shows the normal open form of a three-phase electric motor with 3 rings.

Sometimes, to reduce friction, ball bearings are used, which makes the electric motor about 10% more expensive. It is clear that the use of such electric motors in mill premises, where there is dust or where they may be subjected to blows or jolts, is inconvenient; in view of this, electric motors of the closed type with ventilation are built. In this case either a series of openings (with screens) is arranged directly in the casing of the electric motor, or, if the room is very dusty, branch pipes are fitted (Fig. 22), one of which may be connected with clean outside air.

Fig. 21. Three-phase electric motor of open type.

Fig. 22. Three-phase electric motor of closed type with ventilation.

A special exhaust fan, installed in the casing of the electric motor, draws in this air, expelling it through another branch pipe into the mill room. The suction duct is provided with a special dust-separating screen. This design has the advantage that the motor, on the one hand, is not contaminated by flour dust harmful to it and, on the other, a lighter and cheaper construction is obtained owing to the use of continuous cooling (and, consequently, of conductors of smaller cross-section). Completely enclosed electric motors are also built. Their drawback is that their power (because of heating), for the same dimensions, is lower than that of open motors.

In addition, the heated air during cooling, at the time of stopping, produces a vacuum, each time drawing dust especially into the bearings. The operating personnel are usually reluctant to open them for proper timely inspection.

In view of the fact that the insulation of the winding in electric motors is now made sufficiently strong and is not afraid of dust, from which it is necessary to protect especially only the rings and brushes, particularly because of the danger of explosion (from sparks), motors of the open type are also built, but with

with brushes and rings in a steel casing (Fig. 23). Even if a dust explosion from a spark in the casing should occur, the steel casing will withstand the maximum pressure thereby developed, 8 atm., and there will be no danger in the mill room.

Fig. 23. Three-phase electric motor with rings and brushes brought out and enclosed.

According to D. N. Beckmann*) for mill rooms, usually filled with dust, under normal circumstances, when the possibility of an explosion is not reckoned with (the occurrence of explosions from sparks of electric motors is still a disputed question) and when there is good operating personnel, the most suitable type will be an ordinary electric motor of the normal type.

In order to avoid an excessive accumulation of dust, the electric motor is blown out with a strong jet of air once a week.

In order to have a greater guarantee of safety, electric motors with rings brought out, enclosed in a steel casing, may be used, as was described above (see Fig. 23).

Prof. Dedrick recommends (p. 471) the use of asynchronous electric motors of the enclosed type as the most suitable for flour mills (the polyphase squirrel cage induction motor), since they have no moving parts on the outside and no sparking brushes.

Open-type direct-current motors, in Prof. Dedrick’s opinion, are unsuitable because of the fire hazard.

Although modern direct-current motors are now built with almost complete elimination of sparking at the commutator, there is nevertheless still a danger.

Enclosed-type direct-current electric motors are safe, but this considerably increases both their size and their cost.

Enclosed-type asynchronous electric motors are suitable in flour mills in all cases, and also for elevators, with the exception of installations for overcoming tractive forces (for hoisting, etc.), where a better starting characteristic is required.

The second important feature of electric motors for mills is the necessity for a comparatively small number of revolutions. This feature is caused by the need to connect electric motors in mills directly with the shafts of the main transmissions or with the mill machines.

At present a number of large firms in America (General Electric Co., Allis Chalmers, and others) manufacture electric motors specially for mills.

*) Taschenbuch des Müllers, 1927, p. 234.

Table No. 24.

Alternating-current electric motors used in mills in America.

No.	Power, h.p.	Revolutions per 1 min.	Voltage, volts	Number of periods	Number of poles	Motor type	Make	Purpose
1	150	300	2300	60	24	Supersynchronous	S.E.C.	Direct connection.
2	250	300	2300	60	24	Supersynchronous	S.E.C.	Directly with the rolls.
3	300	240	2300	60	30	Supersynchronous	S.E.C.	Mill, 22 stands
4	400	300	2300	60	24	Supersynchronous	S.E.C.	Mill, 22 stands
5	500	300	2300	60	24	Supersynchronous	S.E.C.	Mill, 22 stands
6	750	257	440	60	28	Supersynchronous	S.E.C.	Mill, 22 stands

In Table 24 we have given certain data for electric motors of this type. It is evident from it that the number of revolutions here is only from 240 to 300 per minute.

Fig. 24 shows an electric motor of 250 h.p. at 300 revolutions per minute, directly connected with the mill transmission.

Fig. 24. Electric motor of 250 h.p. and 300 revolutions per minute, directly connected with the transmission.

Fig. 25 shows an electric motor of 750 h.p. at 257 operating revolutions, with a voltage of 440 volts, at the Midland Milling Co. mill in Kansas, U.S.A.

Fig. 25. A 750 h.p. electric motor at 257 revolutions per minute, directly connected to the mill transmission in the U.S.A.

Fig. 26. A 1200 h.p. electric motor of an American plant.

In Fig. 26 is shown a 1200 ampere electric motor of the Allis Chalmers Co. plant, directly connected with the shaft of the main transmission of a mill having a daily output of 350 tons.

d) Electric motors of the GET plants for mills of the State Electrotechnical Trust.

The GET plants (State Electrotechnical Trust) in the USSR are currently producing (December 1929) electric motors of both open and enclosed types.

For installation in the working rooms of a mill, the most suitable are three-phase GET electric motors of type PRV, with a hermetically enclosed casing, connected with special pipes through which clean air is supplied to cool the motor and the warmed air is removed. These pipes may be made of sheet iron with carefully soldered seams and tight joints (on flanges, etc.), so that mill dust cannot penetrate into them. In order that the electric motor should not overheat, the total length of the supply and exhaust pipes must not exceed 20 meters. Clean air for cooling may be taken from outside or from a room of the mill that is free of dust.

Electric motors of type “PRV” are normally manufactured by GET with slip rings and a device for lifting the brushes and short-circuiting the rotor (starting rotor), but they may also be made with continuously bearing brushes for regulating the number of revolutions.

In the latter case, the use of special starting and regulating rheostats is required, depending on the operating conditions of the motor.

Table No. 25 gives the principal data and prices of motors of type PRV, and Fig. 27 their principal dimensions.

From the table it is seen that motors of type “PRV” are normally manufactured with power up to 100 kW (136 h.p.). By special order the plant manufactures motors of this type also up to 200 h.p.

The normal number of revolutions is 750, 1000, and 1500.

Sketch 1. Design on 2 bearings.

Sketch 2. Design on 3 bearings.

Fig. 27. Diagram and principal dimensions of closed, fan-cooled, three-phase electric motors of type PRV.

In Fig. 28 we have presented a diagram of the cost of 1 h.p. of motors of type “PRV,” the left half of the diagram.

Very recently the Kharkov Electromechanical Plant GET has released a new type of electric motors, “Ut,” representing an electric motor “with a cooled casing,” Mantelgekühlte motoren, as the Germans call them.

The casing of this motor is made double; the inner casing, hermetically enclosing the motor windings, protects them from the penetration of outside air containing dust or moisture and, consequently, from contamination. The upper removable casing forms, between itself and the inner casing, a hollow space through which, by means of a fan installed between them, it is possible to drive cooling air. It is clear that in this case the air may also be taken from the room in which the motor is installed, even if it contains dust, etc., since the motor itself is nevertheless protected by the second inner casing. Thus, when installing motors of type UT, there is no need to arrange ducts supplying clean air, which considerably simplifies their installation as compared with motors of type PRV.

For better cooling of motors of type “Ut”—in addition to the fan between the casings, a second fan is also installed inside the middle inner casing, setting in motion the air enclosed—

Table No. 25. Three-phase electric motors for 500 volts, enclosed, with “PRV” type ventilation, for 1500, 1000, and 750

PRV type	For revolutions per minute	Effective power, kW	Effective power, hp	Revolutions per minute	Normal voltage up to volts	Motor with pulley, without slide rails: weight, approx. kg	Motor with pulley, without slide rails: price, rubles	Belt pulley, normal: diameter, mm	Belt pulley, normal: width, mm	Surcharge for non-normal voltage up to permissible diameter, meter	Price, rubles
For 1500 revolutions per minute
114	— 1500	4,5	6,12	1400	500	200	730.—	150	100	150	7.50
114 a	— 1500	6,8	9,25	1420	500	210	750.—	160	110	160	8.75
134 a	— 1500	10	13,6	1430	500	300	975.—	200	120	180	10.75
134	— 1500	14,5	19,7	1430	500	320	1035.—	240	130	210	21.50
164 c	— 1500	20,5	27,9	1450	500	520	1430.—	260	140	220	25.50
164	— 1500	29	39,4	1450	3000	550	1490.—	300	160	255	36.50
204 e	— 1500	40	54,4	1460	3000	810	1815.—	350	180	310	44.50
204 g	— 1500	56	74,8	1460	3000	875	1985.—	400	200	320	68.—
224 h	— 1500	75	102	1470	3000	1440	2600.—	400	260	350	76.—
224ik	— 1500	100	136	1470	3000	1700	3240.—	450	320	400	—
For 1000 revolutions per minute
114a	— 1000	4,5	6,12	940	500	205	765.—	160	110	140	8.75
134a	— 1000	6,8	9,25	945	500	305	990.—	220	126	200	17.50
134d	— 1000	10	13,6	955	500	335	1065.—	260	140	220	25.50
164c	— 1000	14,5	19,7	960	500	525	1455.—	300	160	250	36.50
164f	— 1000	20,5	27,9	960	3000	560	1545.—	350	180	260	44.50
204c	— 1000	29	39,4	965	3000	800	1825.—	400	200	350	68.—
204g	— 1000	40	54,4	970	3000	865	1930.—	400	200	360	68.—
224h	— 1000	55	74,8	975	3000	1105	2320.—	500	240	420	81.—
224k	— 1000	75	102	980	3000	1350	2790.—	600	320	560	140.—
224k	— 1000	100	136	980	3000	1655	3380.—	600	320	540	140.—
For 750 revolutions per minute
134a	— 750	4,5	6,12	705	500	295	995.—	220	120	180	17.50
134d	— 750	6,8	9,25	710	500	315	1020.—	260	140	200	25.50
164c	— 750	10	13,6	720	500	520	1475.—	300	160	250	36.50
164f	— 750	14,5	19,7	725	500	555	1545.—	350	180	270	44.50
204e	— 750	20,5	27,9	725	3000	810	1935.—	350	180	320	44.50
204g	— 750	29	39,4	725	3000	875	2070.—	450	220	380	77.—
224k	— 750	40	54,4	730	3000	1090	2335.—	500	240	400	81.—
224ik	— 750	55	74,8	730	3000	1340	2815.—	600	320	560	140.—
224n	— 750	75	102	730	3000	1540	3220.—	600	320	560	140.—
264e	— 750	100	136	730	3000	2000	4110.—	650	360	680	190.—

with slip rings, with a device for short-circuiting,
revolutions per minute, manufactured by the “Elektro Sila” plant, Leningrad.

Revolutions per minute	Metal rheostat, for starting with load: half load — type	Metal rheostat, for starting with load: half load — price, rub.	Metal rheostat, for starting with load: full load — type	Metal rheostat, for starting with load: full load — price, rub.	Oil rheostat, for starting with load: half load — type	Oil rheostat, for starting with load: half load — price, rub., without oil	Oil rheostat, for starting with load: full load — type	Oil rheostat, for starting with load: full load — price, rub., without oil	Set of slip rings with brushes and bolts, price, rub.	Type “PRV”
1500	K393 VIB	64.—	K393 XA	88.—	K403 00B	56.—	K403 00A	56.—	53.—	114 —1500
1500	K393 VIIB	90.—	K393 XIIA	135.—	K403 00B	56.—	K403 0A	83.—	53.—	114a —1500
1500	K393 XgC	130.—	K393 XIVA	190.—	K403 00C	56.—	K403 0A	83.—	53.—	134a —1500
1500	K393 XIIgC	175.—	K393 XVIB	255.—	K403 0C	83.—	K44 IB	170.—	53.—	134d —1500
1500	K393 XIVC	190.—	K393 XXA	350.—	K403 0C	83.—	K44 IB	170.—	100.—	164c —1500
1500	K393 XVIC	255.—	K393 XXXA	430.—	K443 IC	170.—	K44 IIA	255.—	100.—	164ef —1500
1500	K393 XXC	350.—	on request		K443 IC	170.—	K44 IIIB	480.—	100.—	204e —1500
1500	K393 XXIIC	430.—	on request		K443 IIC	255.—	K44 IIIB	480.—	100.—	204g —1500
1500	on request		on request		K443 IIC	255.—	K44 IVfB	800.—	100.—	224h —1500
1500	on request		on request		K443 IIIC	480.—	K44 IVfB	800.—	100.—	224ik —1500
1000	K393 VIB	64.—	K393 XA	88.—	K403 00B	56.—	K403 00A	56.—	53.—	114a —1000
1000	K393 VIIIB	90.—	K393 XIIA	135.—	K403 00B	56.—	K403 0A	83.—	53.—	134a —1000
1000	K393 XgB	130.—	K393 XIVA	190.—	K403 00B	56.—	K403 0A	83.—	53.—	135d —1000
1000	K393 XIIgC	175.—	K393 XVIB	255.—	K403 0C	83.—	K443 IB	170.—	100.—	164c —1000
1000	K393 XIVC	190.—	K393 XXB	350.—	K403 0C	83.—	K443 IB	170.—	100.—	164f —1000
1000	K393 XIVC	255.—	K393 XXIIB	430.—	K443 IC	170.—	K443 IIB	255.—	100.—	204c —1000
1000	K393 XXC	350.—	on request		K443 IC	170.—	K443 IIIB	480.—	100.—	204g —1000
1000	K393 XXIIC	430.—	on request		K443 IIC	255.—	K443 IIIB	480.—	100.—	224h —1000
1000	on request		on request		K443 IID	255.—	K443 IVfC	800.—	100.—	224ik —1000
1000	on request		on request		K443 IIIC	480.—	K443 IVfB	800.—	145.—	224k —1000
750	K393 VIC	64.—	K393 XA	88.—	K403 00C	56.—	K403 00A	56.—	53.—	134a —750
750	K393 VIIIC	90.—	K393 XIIB	135.—	K403 00C	56.—	K403 0B	83.—	53.—	134d —750
750	K393 XgC	130.—	K393 XIVB	190.—	K403 00C	56.—	K403 0B	83.—	100.—	164c —750
750	K393 XIIgC	175.—	K393 XVIB	255.—	K403 0C	83.—	K443 IB	170.—	100.—	164f —750
750	K393 XIVC	190.—	K393 XXB	350.—	K403 0C	83.—	K443 IB	170.—	100.—	204e —750
750	K393 XVID	255.—	K393 XXIIIB	430.—	K443 ID	70.—	K443 IIB	255.—	100.—	204g —750
750	K393 XXC	350.—	on request		K443 ID	170.—	K443 IIIC	480.—	100.—	224k —750
750	K393 XXIID	430.—	on request		K443 IID	225.—	K443 IIIC	480.—	100.—	224ik —750
750	on request		on request		K443 IID	255.—	K443 IVfC	800.—	145.—	244h —750
750	on request		on request		K443 IIID	490.—	K443 IVfC	800.—	145.—	264e —750

Three-Phase Current Electric Motors

PRV type and rpm	Sketch	a¹	a	b	c	d	e (norm.)	e₁ (min. permitted)	f	g	i	k	l	m	n
114—1500		326	450	335	523	150	100	150	218	310	370	460	140	60	22
114a—1500 and 1900		〃	〃	〃	〃	160	110	160 | 140	〃	310	〃	〃	〃	〃	〃
134a—1500	1	395	516	405	609	200	120	180	255	375	440	540	180	70	25
134d—1500	1	〃	〃	〃	〃	240	130	210	〃	〃	〃	〃	〃	〃	〃
134a—1000 and 750	1	〃	〃	〃	〃	220	120	200 | 180	〃	〃	〃	〃	〃	〃	〃
134d—1000 and 750	1	〃	〃	〃	〃	260	140	220 | 200	〃	〃	〃	〃	〃	〃	〃
164c—1500		485	625	495	762	260	140	200	326	465	540	650	280	80	25
164f—1500		〃	〃	〃	〃	300	160	255	〃	455	〃	〃	〃	〃	〃
164c—1000 and 750		〃	〃	〃	〃	300	160	250	〃	455	〃	〃	〃	〃	〃
164f—1000 and 750		〃	〃	〃	〃	350	180	260 | 270	〃	455	〃	〃	〃	〃	〃
204e—1500 and 750		516	695	530	885	350	180	310 | 320	377	490	560	760	270	90	28
204g—100 and 1000		〃	〃	〃	〃	400	200	320 | 360	〃	490	〃	〃	〃	〃	〃
204e—1000		〃	〃	〃	〃	400	200	350	〃	490	〃	〃	〃	〃	〃
205g—750		〃	〃	〃	〃	450	220	380	〃	485	〃	〃	〃	〃	〃
224h—1500		555	738	570	981	—	—	350	412	—	570	820	280	100	28
224h—10000, 750		〃	〃	〃	〃	500	240	420 | 400	〃	525	〃	〃	〃	〃	〃
224ik—1500	1	595	778	610	983	—	—	400	414	—	650	820	360	100	28
224ik—1000, 750	1	〃	〃	〃	〃	600	320	560	〃	565	〃	〃	〃	〃	〃
244k—1500		645	855	660	1059	—	—	420	446	—	760	890	420	100	28
244k—1000, 750		〃	〃	〃	〃	600	320	540 | 560	〃	615	〃	〃	〃	〃	〃
264l—1000		698	925	715	1144	—	350	480	478	—	830	960	470	110	32
264l—750		〃	〃	〃	〃	650	—	630	〃	630	〃	〃	〃	〃	〃
264m—750		718	945	735	1145	800	360	760	479	650	870	960	510	110	32
284n—750		780	1070	795	1213	—	—	750	525	〃	920	1060	560	110	32

Note. Dimension a¹ is for squirrel-cage electric motors.
Dimension C is for electric motors with slip rings and a device for lifting the brushes.
The double dimension e₁ refers to speeds of 1500 and 1000, 1000 and 750.

PRV type and rpm	Sketch	a	c	d	e (norm.)	e₁ (min. permitted)	f	g	i	k	m
224h—1500	2	738	981	400	260	350	412	525	105	115	190
224ik—1500	2	778	983	450	320	400	414	565	105	115	190
244k—1500	2	855	1059	500	350	420	446	615	115	130	230
264l—1000	2	925	1144	600	360	480	478	630	130	142	250
284n—750	2	1070	1213	900	450	750	525	700	135	154	250

closed, with ventilation, type PRV

o	p	q	r	t	A	B	C	H	E	L	M	N	R	S	T	U	V	W	X	Y	Z
260	38	100	10	3	280	360	589	240	320	850	70	—	—	250	175	290	240	609	16	60	13
”	”	”	”	”	”	”	”	”	”	”	”	—	—	”	”	”	”	”	”	”	”
300	48	120	12	3,5	340	420	689	80	365	850	70	—	—	250	175	290	240	609	16	60	130
”	”	”	”	”	”	”	”	”	”	”	”	—	—	”	”	”	”	”	”	”	”
”	”	”	”	”	”	”	”	”	”	”	”	—	—	”	”	”	”	”	”	”	”
”	”	”	”	”	”	”	”	”	”	”	”	—	—	”	”	”	”	”	”	”	”
390	58	150	15	5	440	520	855	350	465	1150	80	50	110	275	250	700	620	800	19	70	180
”	”	”	”	”	”	”	”	”	”	”	”	”	”	”	”	”	”	”	”	”	”
”	”	”	”	”	”	”	”	”	”	”	”	”	”	”	”	”	”	”	”	”	”
”	”	”	”	”	”	”	”	”	”	”	”	”	”	”	”	”	”	”	”	”	”
470	68	170	18	5,5	450	610	963	410	536	1150	80	50	110	275	250	700	620	800	19	70	180
”	”	”	”	”	”	”	”	”	”	”	”	”	”	”	”	”	”	”	”	”	”
”	”	”	”	”	”	”	”	”	”	”	”	”	”	”	”	”	”	”	”	”	”
”	”	”	”	”	”	”	”	”	”	”	”	”	”	”	”	”	”	”	”	”	”
500	78	200	20	6	460	660	1026	450	574	1150	80	50	110	275	250	700	620	800	19	70	180
”	”	”	”	”	”	”	”	”	”	”	”	”	”	”	”	”	”	”	”	”	”
500	78	200	20	6	540	660	1026	450	599	1150	80	50	110	275	250	700	620	800	19	70	180
”	”	”	”	”	”	”	”	”	”	”	”	”	”	”	”	”	”	”	”	”	”
570	88	220	22	6,5	650	730	1110	470	634	1400	100	60	130	300	250	850	760	1000	23	80	190
”	”	”	”	”	”	”	”	”	”	”	”	”	”	”	”	”	”	”	”	”	”
600	98	240	24	7,5	710	780	1169	500	685	1400	100	60	130	300	250	850	760	1000	23	80	190
”	”	”	”	”	”	”	”	”	”	”	”	”	”	”	”	”	”	”	”	”	”
600	98	240	24	7,5	750	780	1169	500	686	1400	100	60	180	300	250	850	760	1000	23	80	190
700	105	260	26	8	800	880	1255	550	715	1700	130	70	150	325	300	1000	900	1200	26	90	220

In millimeters

A	C	H	E	L	M	N	R	S	T	U	V	W	X	Y	Z
550	1026	450	574	1150	80	50	110	275	250	700	620	800	19	70	180
620	”	”	599	”	”	”	”	”	”	”	”	”	”	”	”
680	1110	470	634	1400	100	60	130	300	250	850	760	1000	23	80	190
725	1169	500	685	”	”	”	”	”	”	”	”	”	”	”	”
830	1255	550	715	1700	130	70	150	325	300	1000	900	1200	26	90	220

inside the motor and driving it through special tubes laid along the surface of the inner casing and washed by the external air passing between the motor casings.

Fig. 28. Cost of 1 horsepower of three-phase-current electric motors of the GET plants.

As a result of the intensive cooling of motors of the “Ut” type, the material in them is used more rationally, and in dimensions they differ very little from normal open electric motors.

At present the GET has released motors of the “Ut” type in the following sizes:

From 4.5 kW to 75 kW at 1450 revolutions per minute.
” 4.5 ” ” 54 ” ” 965 ” ”
” 4.5 ” ” 40 ” ” 730 ” ”

The scale of powers between the above-mentioned limits coincides with the powers of motors of the “PRV” type. In the future it is planned to manufacture motors of this type in higher powers.

It is also necessary to add that the slip rings of the “Ut” type motors are brought out from the motor casing beyond the bearings and are located at the end of the shaft in a hermetic box. This makes it possible to inspect and replace the brushes very conveniently without disassembling the entire motor casing. The only exceptions are small electric motors of 4.5 horsepower, where in order to inspect the motor it is necessary each time to disassemble the casing; but, owing to the small dimensions of these motors, this does not present any particular difficulty.

Open-Type Electric Motors

For directly setting in motion the main transmissions of a mill, electric motors of considerable power are for the most part required (150–400 hp), with a comparatively small number of revolutions (in installations in the USSR, 375 rpm is often used). Such motors are made by GET as open-type motors and are usually installed in separate rooms, carefully insulated from the other dusty working rooms of the mill.

Table No. 26 gives approximate data for this type of “D” motors.

From the note in the table it is seen that the starting torque here is guaranteed from 2.0 to 2.5 times the normal rotating torque, at the specified power; but by special order, with an extra charge of about 30%, motors can be made with a threefold rotating torque.

The comparative cost of 1 horsepower of motors of the “D” type is seen from Fig. No. 28 (right-hand part of the diagram). It is seen from it that the cost of 1 hp of these motors is somewhat less than that of electric motors of the enclosed “PRV” type.

Starting Rheostats, Distribution Boxes, etc.

For starting electric motors installed in mills, it is essential to use tightly enclosed rheostats with oil cooling for the full starting torque that must be developed by the motor when starting into operation. If this starting torque is higher than normal, it must be specially specified when ordering the motor.

It should be borne in mind that the normal starting torque of three-phase electric motors when started with a rheostat is about 1.4 to 1.6 of the normal operating rotating torque corresponding to the normal power of the electric motor.

Table No. 26. Indicative data for three-phase, 50-period, 3000 V, open-type “D” motors, enlarged versus the normal starting torque of the Kharkov Electromechanical-Machine-Building Plant “GET”

Number of revolutions per min. (synchronous)	Power, hp	Approximate cost in rubles: motor	Approximate cost in rubles: starting rheostat	Efficiency in % at load 1/1	Efficiency in % at load 3/4	Efficiency in % at load 1/2	Power factor (cos φ) at load 1/1	Approximate dimensions in mm: length along axes	Approximate dimensions in mm: width of shaft center	Approximate dimensions in mm: overall height	Approximate weight in kg	Approximate price with starting rheostat and oil can, rub.
1000	400	7950	2430	92,5	92	91,5	0,91	1960	1320	620	4220	10630
1000	225	5700	775	92	91,5	91	0,91	1925	1180	600	2950	6725
1000	175	4200	775	91,5	91	90	0,9	1790	1010	500	2400	5175
1000	150	3850	775	91,5	91	90	0,9	1745	1010	500	2150	4770
750	400	9350	2430	92,5	92	91,5	0,91	1495	1520	700	4600	12030
750	225	6400	775	92	91,5	91	0,9	1505	1160	600	3100	7425
750	175	4650	775	91,5	91	90,5	0,85	1425	1160	600	2610	5625
750	150	4230	775	91,5	91	90,5	0,85	1385	1160	600	2350	5150
600	400	10700	2430	91,5	91	90,5	0,9	1570	1520	750	5100	13430
600	225	7520	775	91,5	91	90,5	0,9	1430	1320	750	3750	8925
600	175	5200	775	91,5	90	89,5	0,85	1360	1320	750	2850	6175
600	150	4800	775	91,5	90	89,5	0,85	1505	1160	600	2600	4750
375	400	16200	2430	91,5	91	90,5	0,85	1880	2350	1010	7210	18930
375	225	9800	775	90,5	90	89,5	0,84	1575	1700	980	3800	10225
375	175	8360	775	90,5	90	89,5	0,83	1495	1700	980	3350	9355
375	150	7800	755	90	89,5	89	0,83	1445	1700	980	3100	8750

NOTES:
1. Prices and dimensions are given for motors made with two end shields and a free shaft end (without shield).
2. The weights shown in the table are the synchronous weights; the working number of revolutions of the motor is approx. 3% lower than the synchronous value.
3. The starting torque may be guaranteed as:

for motors of 1000 and 750 rev/min. — 2.5 times the normal at rated power

for motors of 600 rev/min. — 2.2 times the normal at rated power

for motors of 375 rev/min. — 2 times the normal at rated power

Tolerance ±10%.

1. To start a type “D” motor, a special-type oil starter should be used. In this case, a starter of lower power than that corresponding to the specified power may be used; above the rated power by 30%, and orders may be accepted in quantities of not less than 3 units simultaneously.
2. Motors are supplied with starting rheostats for starting them at idle speed (see note 3).
3. Motors for voltages of 6000 V are manufactured by the plant; that is, 175 hp and above. Their cost is 2% higher than the price of a 3000 V motor.

For switching electric motors on and off at the point of installation in mills, and for monitoring their load, it is necessary to use special cast-iron or iron tightly closing distribution boxes. The necessary apparatus is placed in the boxes and is thus protected from dust and contamination.

The GET factories produce the following types of distribution boxes:

Figure No. 29. Cast-iron distribution boxes of the GET factory (external view).

A. Low voltage up to 550.

1. Type III A—with built-in:

a) three-pole knife switch.
b) ” fuse.
c) ” ammeter.

Distribution box for 60 and 100 amp.

Distribution box for 200 amp.

Three-pole.
Distribution box for 60 and 100 amp.

Two-pole.

Three-pole.
Distribution box for 200 amp.

Two-pole.

Figure No. 30. Distribution boxes of type A.

These boxes are built for current ratings up to 25, 60, 100, and 200 amperes. The figure indicating the current rating for which the box is intended is placed to the right of the type designation: e.g., III A—60. If desired, these boxes can be supplied with a voltmeter or without an ammeter. The box is arranged so that the door cannot be opened when the switch is closed, and the switch can be switched on only when the box door is closed.

GET distribution boxes. Type III A
(three-pole).

Type	Current rating, amp.	Weight, kg	Price, rubles
IIIA 60	60	30	125
IIIA100	100	46	190
IIIA200	200	104	290

1. Type IIIAC with built-in:

a) maximum-zero automatic circuit breaker,
b) ammeter and, if desired, voltmeter.

These boxes are built up to 100, 200, and 400 amperes.

GET distribution boxes. Type III AC
(three-pole).

Type	Current rating, amperes	Volts	Weight, kg	Price, rubles
III AC 100	100	500 750	110	610 680
III AC 200	200	500 750	120	640 655
III AC 400	400	500 750	140	790 835

A type “C” automatic circuit breaker is built into the box—maximum-zero, with magnetic arc extinction and an ammeter.

Maximum tripping is effected in two phases; the zero-voltage coil is connected between two phases.

The automatic circuit breaker has free tripping, thanks to which the possibility of prolonged intentional switching-on under short-circuit or overload conditions is eliminated.

In the absence of voltage, the automatic circuit breaker cannot be switched on.

3. JAMMI type with built-in:

a) three-pole switch placed in an oil tank,
b) maximum-zero automatic device for switching off the knife switch in case of overload.

These boxes are built for a current strength of up to 200 amperes.

B. High-voltage boxes.

1. TYPE “S No. 7”—for 3300 volts
with built-in:

a) oil switch with automatic maximum-zero closing and time delay,
b) three-pole disconnector,
c) current and voltage transformers,
d) ammeter and, if desired, voltmeter,
e) two cable couplings.

With the maximum power of high-voltage mill motors being 450 h.p., a box of sufficient type for an operating current of 200 amperes is adequate. The price of such a box is 1350 rubles.

2. TYPE “YaZh—5”—for 6600 volts, in which the same fittings are built in as in box “S No. 7.” The cost of the box “YaZh—5” for an operating current strength of up to 200 amperes is about 2000 rubles.

Fig. No. 31. Distribution boxes of type AS.

3. General arrangement of electric transmission in flour mills.

Single or group electric motors in flour mills.

The transmission of energy in a mill is characterized above all by the fact that the machines here, or groups of them, must operate simultaneously. The energy consumption of individual machines is in most cases comparatively small. The number of revolutions of the working machines of a mill is usually less than that of standard electric motors.

Taking this into account, it is more rational to use either a group system of arrangement of electric motors, or one electric motor for the whole mill. To apply the individual method of transmission, installing for each separate mill machine its own electric motor, is obviously irrational for flour mills; but in certain cases, where excessively long transmissions are required, as for example to exhausters, conveyors, etc., it is more rational to install separate electric motors.

Installation of Electric Motors in a Mill

Fig. 33 shows the schematic arrangement for transmitting energy in a flour mill from electric motors.

As is easily seen from the diagram, various combinations are possible here.

On the lower first floor at the left, two electric motors No. 1 and No. 2 are shown in side view (they are visible, one behind the other, from the end of the shaft, in the middle of the drawing), and above them is part of the side transmissions.

Motor No. 1 can transmit motion to the shaft of the main transmission A and from it, by belts or ropes, to the auxiliary transmission B and from it to the auxiliary transmission C on the IV floor.

From this same shaft A of the main transmission it is possible to transmit motion (by a belt or ropes) G—in the figure by a dotted line—to the shaft of the main transmission D (on the 1st floor). And from shaft D to shafts E and F.

Thus this will be a scheme for setting the whole mill in motion from one electric motor.

Fig. 32. Diagram of connections in distribution boxes of type AC.

It is also possible to install on the 1st floor two electric motors No. 1 and No. 2 and, eliminating the belt transmission G, to rotate each transmission from its own electric motor. At the same time it is also possible—and this is often done at present—that these motors are connected directly to the shafts of the main transmission (without transmission gearing).

It is possible to install on the 3rd floor electric motor No. 3, which will independently set transmissions B and C in motion; then, of course, transmission L is superfluous.

It is possible to install electric motor No. 4 on the IV floor (in the figure, at the right), with transmission of motion to transmissions F and E and with transmission M disconnected.

It is also possible to install individual motors for separate mill machines, and other various combinations.

Machines such as roller mills and the like are better driven from transmission shafts in groups, transmitting the motion by belts. Such groups of machines are convenient in a mill. Moreover, an individual drive is more convenient because, owing to the connection of the machines with one another, otherwise, when one of the machines stops, it will be started while the group is operating.

The best method is a combination of group and individual transmission: individual drives, it is true, reduce transmission and friction, but modern

transmissions on balls have reduced friction losses to a minimum.

Although, with the use of slow-running electric motors directly connected to the mill transmission shafts, the intermediate belt or rope drive is eliminated, and thus the entire arrangement is seemingly simplified and the efficiency increased, this advantage is still in many cases open to question, since with a reduction in the speed of the electric motors their $\cos \varphi$ and their efficiency decrease, the starting torque falls (for example, at $n = 750—1000$, $M = 2.5$; at $n = 600$, $M = 2.2$; and at $n = 375$, $M = 2.0$), and finally the cost of such electric motors rises. Meanwhile the efficiency of belt transmission has a rather considerable value (for example: $\eta = 0.96—0.97$), and its use makes it possible to install cheaper and more economical high-speed electric motors and creates a whole series of conveniences.

The convenience of using electric motors consists in the free arrangement of the working machines and in reducing the length of belts.

The advantage of electrification is that, if different groups of machines operate from separate electric motors, then when new machines are installed they can be started with an individual drive without interrupting the operation of the remaining machines.

Individual drive by separate electric motors is convenient for machines that stand apart and have a large number of revolutions, such as, for example, exhausters, etc.

Prof. Dedrick, for mills of small and medium capacity, prefers driving the entire mill by one electric motor. The friction loss in transmissions, with the present use of improved ball and roller transmissions, has been reduced, as already stated, to a minimum.

When applying group drive, subdivision into groups, or especially transition to individual drive, should be done only in cases of necessity and rationality.

Engineer A. E. Hall, head of the milling-machinery department of the large American firm Allis—Chalmers Manufact. Co*) likewise considers it irrational to use individual transmission from separate electric motors to the machines of flour mills, and regards the group system as the most rational. In this connection he considers it possible to distinguish the following groups of machines in mills:

1. The grain-cleaning department, and in large mills also the department for receiving grain (elevator).
2. Roller mills or crushers.
3. Sifting machines and aspirators, bucket elevators, conveyors, and in general all machines located in the grinding department of the mill above the roller mills.
4. On navigable rivers and at harbors—hoisting cranes.

Transmission of Motion from Electric Motors.

Transmission of motion from electric motors to working machines or transmissions is carried out, as stated above, either by direct connection or by means of pulleys and belts.

) See Standart Handbook for Electrical Engineers* Sec. 15—433.

With electric motors up to 150 h.p. and 1000 r.p.m., an overhung pulley on the end of the shaft is used. At higher powers, a supporting bearing is usually arranged on the other side of the pulley, or even two standards are used, one on each side of the pulley (Fig. 34).

Fig. No. 33. Diagram of the installation of electric motors in a mill.

Diameters of shafts, number of revolutions of the pulley, etc.

The diameter of the transmission shafts of a mill may be determined by using the formula:

\[ d = 120 \sqrt[4]{\frac{N}{n}}, \quad \text{where} \]

\(d\)—diameter of the shaft in millimeters,

\(N\)—transmitted power in effective horsepower,

\(n\)—number of revolutions of the shaft per minute.

To facilitate calculations, a table is given at the end of the book (see the general section). There are also tables of normal pulley dimensions, normal numbers of shaft revolutions, etc.

With respect to the dimensions and ratios of pulley diameters, etc., the same rules apply here as generally for belt transmission.

When it is necessary to make the transmission ratio very large (up to \(1:20\)) with a small distance between the pulleys of the electric motor and the transmission, an idler pulley is used.

Couplings are of the fixed and movable types. The former may be used in those cases when the electric motor stands on a common plate with the shaft of the working machine or transmission to which it transmits motion.

Elastic couplings are used when there is no entirely rigid connection of the electric motor, or when shocks occur.

Installation of Electric Motors

Installation on a plate and slide rails (Fig. 35) for possible belt tightening.

Or, in the case of direct coupling, installation on cast-iron pedestals (Fig. 36).

Fig. 34. Three-phase motor with an additional side bearing.

Fig. No. 35. Electric motor on slide rails.

Fig. 36. Cast-iron pedestal for installing an electric motor.

General Principles for Arranging Transmission from Electric Motors in Mills

Taking into account what has been stated above, and making use of the experience of America, where more than half of all mills have already been electrified, the following general principles may be adopted in arranging transmission from electric motors in mills:

1. Electric energy, through high-voltage wires, usually first arrives at a substation, where the main—

a step-down transformer and a main distribution board, from which the electric energy is distributed at the operating voltage (6000–220 volts) to the individual principal motors and departments (groups of motors) of the enterprise.

The main distribution board of the substation makes it possible to monitor the operation of the entire enterprise and to keep an account of the energy consumed.

1. At the points of principal energy consumption in the enterprise, separate electric motors are installed: for group drive, for example, a separate electric motor is installed in the grain-cleaning department (14–19% of the total mill power), and several separate electric motors are connected directly to the transmission shafts in the rollers. These motors are usually located, several at a time, on the side of the workroom and operate at an operating voltage of 2300–3000 volts.

Sifting machines, fans, and elevators are also often combined into a separate common group, having one common electric motor. And finally, to set in motion individual, comparatively small milling machines (exhausters, etc.) and auxiliary devices (conveyors, etc.), a number of separate electric motors are also installed directly at these machines (operating voltage 380–440 volts).

Sometimes the group of these motors is served by an additional auxiliary distribution board located in the mill, which makes it possible to monitor their operation.*)

1. The machines and auxiliary devices belonging to the mill—elevators, grain dryers, etc.—are driven, according to the principle set forth above, by a number of separate, more substantial or small electric motors.

Thus, in general, a well-ordered system is obtained of a series of electric motors, the operation of whose groups can be regulated and observed at local distribution boards, and of the principal motors with monitoring at the main distribution board.**)

The continuous monitoring and accounting of the energy consumed by the individual parts and machines of the mill, when it is electrified, here makes it possible during operation to watch easily over the normal and uninterrupted functioning of all its separate machines and mechanisms, eliminating defects in good time.

In the case of single drive, for the main electric motor driving the entire mill, Eng. A. Hall recommends, when its power is not more than 700 hp, using a three-phase asynchronous electric motor with a phase-wound rotor, having slip rings with a rheostat, allowing the resistance to be varied during starting (slip-ring induction motor).

The distribution equipment must include oil switches with automatic devices protecting the electric motors against overload and accidental voltage drops in the main line.

Electric motors of lower power may be asynchronous, of the enclosed type.

*) See Chapter V. Examples of electrified mills, where a series of electric motors connected with groups of machines is given.

**) The division into groups by power may greatly facilitate the table No. 22 of energy distribution compiled by us, given in Chapter II.

CHAPTER IV.

Electric Lighting of Mills.

In recent times, ever greater importance has been attached to the lighting of industrial enterprises. The German scholar Eshleman*) believes that an enterprise can obtain the highest output of the best quality only when it has the principal factors:

1) good machines,
2) good workers, and
3) good lighting.

If one of these factors is lacking, then the other two, however high they may be, lose their significance.

It has already been proven that good lighting in industrial enterprises entails:

1) a reduction in the number of accidents,
2) mitigation of the consequences of accidents,
3) preservation of workers’ health,
4) an increase in labor productivity,
5) improvement in the quality of products,
6) a reduction in rejects,
7) promotion of cleanliness and neatness in the premises.

The milling industry is highly mechanized, but nevertheless everything said above regarding lighting is applicable for the most part to this kind of production as well.

And, indeed, the practical and calculating Americans pay very great attention to good lighting of mills, adopting, according to the American lighting code (Code of Lighting), for mills and groat works an illumination of 22 to 54 lux (for the meaning of the unit lux, see below), and going up to 100 lux when the walls are finished with white marble or tile and the ceiling with white enamel.

The English and German illumination standards for mill premises are also high.

We, unfortunately, are still behind in the illumination of milling enterprises.

Thus, an examination of the illumination of mills No. 89 and No. 92 in Nizhny Novgorod, carried out by the Nizhny Novgorod occupational dispensary,**) showed that, with daylight in the yard of 280–2059 lux, the average illumination in the mill premises was determined as:

) E. Balakshin, “Daylight Lighting of Industrial Buildings.”
*) See the report of this examination.

Table No. 27.

Average illuminance data in lux for mills Nos. 89 and 92
in Nizhny Novgorod.

According to the report of the Nizhny Novgorod occupational-health dispensary.

Type of room	Daylight	Electric
1) Elevator	from 0.8 to 18.8	0.7 to 2.4
2) Grain-cleaning department	1.2 to 5.2	1.2–3.4
3) Roller department	2.0 to 2.6	—
4) Milling building	1.2 to 5.7	1.0 to 4.2

From this Table No. 27 it is evident how still insufficient, at the present time, the lighting of our mills is—not only in comparison with American mills, but even with the minimal standards presently adopted here, of 8 to 35 lux (see below).

The Nizhny Novgorod occupational-health dispensary draws the following conclusion from its survey of the lighting of mills in Nizhny Novgorod.

1) Lighting, both daylight and electric, is insufficient; it must be increased to 20 lux (taking into account the percentage of light absorbed by dust).

2) It is necessary to re-equip the lighting according to a definite technical calculation, so that it will be uniform.

3) The lighting fixtures must be reconstructed so that the light will be diffused.

4) It is necessary to assign a person who would see to the cleanliness of the windows and fixtures, cleaning both at definite intervals.

“Soap and water are cheaper than electric energy,” as Halberstein says in his book Factory Lighting.

From the conclusion cited it is clear that, in addition to the insufficiency of the illuminance of the Nizhny Novgorod mills, it is nonuniform; moreover, the fixtures (and the windows) are not cleaned in due time, nor are the walls, which absorbs much light, thereby reducing the illuminance with a useless expenditure of energy.

What has been stated above regarding the illuminance of the Nizhny Novgorod mills, unfortunately, can at present also be applied to the majority of our mills.

It is therefore impossible not to welcome the illumination standards for milling enterprises developed by the Commissariat of Labor of the USSR on September 17, 1928, No. 545, with additions, amendments, and detailing by the Scientific-Technical Council for the Flour-Milling Industry under the People’s Commissariat of Trade of the USSR, agreed with the People’s Commissariat of Trade of the RSFSR (see below, Table No. 28, on p. 73). It is also necessary to welcome the effort of the Joint-Stock Company “Soyuzkhleb,” which has the majority of the USSR’s commercial mills, to regulate the question of lighting not only at newly designed mills, but also to carry out reconstruction of lighting at all mills.

The foregoing sufficiently emphasizes the importance of electric lighting in the electrification of mills, in view of which we give below the principal foundations of lighting engineering and of the design of mill lighting.

Principal Units of Light

The unit of luminous intensity adopted by the International Congress of Electricians in 1888 is 1 candle (c.), equal to 1 : 20 Violle, i.e., the luminous intensity emitted by 1 cm² of molten platinum in the direction perpendicular to its surface, at the moment of solidification.

In Germany, the luminous intensity of a special Hefner–Alteneck lamp is adopted as the unit of luminous intensity. This candle, denoted IHK, is called 1 Hefner, wherein:

\[ \mathrm{IHK} = 0.9 \ \text{c.} \]

The International Congress on Illumination in Paris in 1921 established the following photometric units:

Luminous flux \((F)\) is the sum of the luminous energy, measured according to the visual sensation that it produces.

Lumen (lm) is the unit of luminous flux.

The lumen is equal to the flux of light emitted within a solid angle equal to unity, uniformly in all directions, by a luminous source of intensity 1 international candle.

Note. A solid angle equal to unity is taken to be the angle within the conical surface formed by the tracing of the radius of a sphere \(Oa = 1\) meter, if its end \(a\) describes a circle cutting off from this spherical surface an area of 1 sq. meter. Fig. 37.

Illumination \((E)\) of any plane is the density of the luminous flux at this point, or the quotient of the division of the luminous flux by the area of the illuminated surface, if it is uniformly illuminated.

Lux is the unit of illumination, equal to the illumination of a surface of 1 square meter by a uniformly distributed luminous flux of 1 lumen; or, a lux corresponds to the illumination of the surface of a sphere if at its center there is a uniformly radiating source of light with intensity of 1 international candle.

Thus,

\[ E = \frac{F}{S} \]

where:

\(E\) — illumination in lux,

\(F\) — luminous flux in lumens,

\(S\) — area of the illuminated surface.

Fig. 37. A solid angle equal to unity within a conical surface formed by the tracing of the radius of a sphere \(oa = 1\) meter, the end of which describes a circle cutting off from the spherical surface an area of 1 sq. meter.

Illumination is inversely proportional to the square of the distance \(r\) from the light source and, in addition, depends on the cosine of the angle \(\alpha\) of incidence of the rays, i.e.,

\[ E = \frac{F}{r^2}\cos \alpha \]

Brightness, of a completely diffusing surface emitting or reflecting one lumen from \(1\ \mathrm{cm}^2\), is called a lambert (Lambert), denoted lmb. Sometimes brightness is defined by the luminous intensity emitted by \(1\ \mathrm{cm}^2\) of a luminous surface in the direction perpendicular to this surface (\(1\ \mathrm{lm}/\mathrm{cm}^2\)).

Reflection and scattering of the luminous flux*).

Light falling on some polished, reflecting surface is partly reflected by it, as, for example, the following reflect:

Silvered mirror . . . . . . 80–88%
Amalgamated . . . . . . . . 70%

Unpolished surfaces absorb part of the light, scattering the remaining part; for example:

Purely whitewashed wall scatters . . . . 75%
Brown paint . . . . . . . . . . . . . . . 40%
Black cloth . . . . . . . . . . . . . . . 1.2%

Design of Electric Lighting for Flour Mills.

It has already been indicated above that lighting of mills is of great importance; in view of this, proper attention must be given to the design of electric lighting for new mills and to the reconstruction of existing electric lighting.

This lighting of mills must be designed or reconstructed in such a way that in all its working rooms, in passageways, warehouses, in the yard, living quarters, etc., there shall be:

1) sufficient illumination and its uniformity, with rational use of electrical energy;

2) the electric lighting of the mill must be safe with respect to fire and convenient for maintenance.

According to the minutes of the meeting of the Main Technical Inspectorate of the People’s Commissariat of Labor of the USSR of 8/VIII—1929, on the application of “Soyuzkhleb” concerning the lighting of mills, it was resolved:

1) As the basis for calculating electric lighting in mill premises, the minimum illumination along the line of passage is to be taken as 8 lux on the floor (§ IX of the rules of the People’s Commissariat of Labor of the USSR, of 17/IX—1928).

2) The maintenance factor must be taken as not less than 1.5.

3) The fittings used must be hermetic, or for outdoor lighting without an opening in the shade.

4) In all other respects, the requirements of the above-mentioned rules of 17/IX—1928 must be observed.

Independently of this, the Design Bureau of “Soyuzkhleb” recommends the following when installing electric lighting in mills:

Choose hermetic fittings (the most suitable being the “Universal” or No. 1231 according to the GET catalog).

Lay the internal wiring with lead-sheathed cable of the SRGN type. Use hermetic group switchboards and enclose them in iron boxes. It is best to use standard GET distribution boxes of type VL.

*) See Prof. P. A. Korolkov, Course of Electric Lighting, p. 23.

Emergency safety lighting (0.5 lux in passages, green lamps at exits) is to be supplied from a separate riser. Lamps should, if possible, be taken not less than 100 watts for normal lighting. In high rooms of 4.5–6 meters it is better to use lamps of 150–200 watts.

Calculation of Mill Lighting

The required luminous flux in lumens is determined by the formula

\[ F=\frac{K \times E \times S}{\eta} \]

where

\(K\) — reserve factor for the reduction of luminous flux due to soiling of lamps and wear of incandescent filaments.
For milling enterprises take \(K = 1.5\)

\(E\) — illumination in lux according to the adopted standards (see Table No. 28).

\(S\) — illuminated area in square meters.

\(\eta\) — coefficient of utilization of the luminous flux \(ES\) falling on the illuminated surface \(S\) to the total flux \(F\) emitted by all the installed bare lamps, i.e.

\[ \eta=\frac{E \times S}{F} \]

The utilization coefficient is determined from Tables Nos. 29–30, according to the selected lighting fixtures, the condition of the paint of the walls and ceiling, and the values of the so-called room indices (indicators) (see Table No. 31).

The room index characterizes the ratio of the width of the (square) room to the height of the light source above the illuminated surface. The room index is determined differently depending on whether: 1) direct lighting or 2) reflected or semi-diffused lighting is used.

For direct lighting of a square room of width \(b\), the index is

\[ \rho_b=\frac{b}{2h} = \frac{\text{width of the room}}{\text{twice the height of the light source above the illuminated surface}}. \]

With semi-reflected and reflected lighting, the index of a square room of width \(b\) is equal to the ratio:

\[ \rho_b=\frac{b}{\frac{4}{3}h} = \frac{\text{width of the room}}{\text{four thirds of the height of the light source above the illuminated surface}}. \]

If the value of the index is greater than 5, the index is taken as 5.

These indices characterize a square room.

If the room is rectangular, of width \(b\) m and length \(l\) m, then first the index \(\rho_b\) is found for a square room with side \(b\), and then the index \(\rho_l\) with side \(l\); and for each of these indices the corresponding values of the utilization coefficients \(\eta_b\) and \(\eta_l\) are found from the tables. Then the luminous-flux utilization coefficient for this rectangular room is determined from the formula:

\[ \eta=\frac{2}{3}\eta_b+\frac{1}{3}\eta_l \]

where:

\(\eta_b\) — utilization coefficient for a square room with sides \(b\)
\(\eta_l\) — utilization coefficient for a square room with sides \(l\)

The values \(\eta_b\) and \(\eta_l\) are determined, as stated above, from tables corresponding to the selected lighting fixtures, the condition of the painting of the walls and ceiling, and the values of the calculated indices.

Height of lamp suspension and distance between them.

Direct-light lamps must be hung at the ceiling itself.

It has been agreed that the suspension height of lamps \(H\) is to be measured not from the floor, but from the working surface (usually 1 meter from the floor) to the center of the lamp (see Fig. 38).

Diffusing luminaires are usually hung from the ceiling at a distance of \(1/4\) to \(1/3\) of the height \(H\) of the room to the working surface, so that they illuminate the entire ceiling (Fig. 39).

The distance between lamps is determined by the uniformity of illumination and is taken as approximately 1.5 times greater than the suspension height \(H\) of the lamps.

The distance of lamps from the walls is made equal to \(1/2\) of the distance between lamps (where there are machines—\(1/3\)).

Fig. 38. Arrangement of direct-light lamps.

Fig. 39. Arrangement of diffusing-light lamps.

Direction and diffusion of the luminous flux (reflectors, fittings).

Existing light sources usually do not provide the desired distribution of light for particular individual cases; therefore, the desired distribution has to be achieved with the aid of special reflectors and fittings.

In addition to ordinary lampshades, the State Electrotechnical Trust (GET) has developed a whole series of special fittings for their use in lighting various factory and mill premises. Here we give a description of the most commonly used of them.

The “Universal” lighting fixture.

The “Universal” fixture, shown in Fig. 40, is manufactured either with a glass hood (shade) (Fig. a), or without a shade (Fig. b).

The “Universal” fixture with a glass hood is especially suitable for lighting the interior rooms of such industries as flour milling, where dust is released which, in the absence of a hood, easily—

... as it burns onto the surface of the bare lamp and may even ignite. The globe may be made of transparent or frosted glass.

Without a glass globe, the “Universal” is used for lighting non-dusty workrooms up to 5 meters high.

Fig. 40. “Universal” lighting fixture.
a—With shade
b—Without shade
c—General arrangement

The “Universal” fixture is manufactured for lamps:

up to 100 watts—360 mm in diameter
up to 200 watts—420 mm in diameter
up to 500 watts—475 mm in diameter

“Lucetta” Lighting Fixture.

The “Lucetta” lighting fixture (Fig. 41) consists of two glass parts fastened together by a metal rim.

“Lucetta” gives good diffuse light, under which shadows disappear in the room and the walls and ceiling are well illuminated.

Depending on the type of glass used, it is possible to direct the luminous flux in different ways. If, for example, the upper glass is taken as frosted and the lower as opal, then the light is directed chiefly upward, toward the ceiling. If, on the other hand, the upper is opal and the lower frosted, then the light is directed downward. The “Lucetta” fixture is made for lamps up to 100 watts, having 250 mm diameter and 350 mm height, and for 200 watts, 315 mm diameter and 400 mm height. Because the “Lucetta” fixture gives an even diffuse light, it is very convenient for lighting offices, living quarters, etc.

Fig. 41. “Lucetta” lighting fixture
a—diagram,
b—external view.

“Bilux” Lighting Fixture.

The “Bilux” lighting fixture consists of two reflectors, which are made either of enameled iron or with the lower one of glass.

“Bilux” is used in rooms whose height is less than 5 m, in which there is no dust, and is made for lamps up to 300 watts.

Table No. 31 gives the utilization coefficients for the principal lighting fixtures of the GET.

Nonuniformity of Illumination *).

Illumination, so as not to strain the eyes and to increase distinctness of vision, must be uniform.

As the measure of nonuniformity of illumination, the ratio of the greatest illumination \(E\) max. to the least illumination \(E\) min. is taken.

Permissible nonuniformity of illumination.

Quality of illumination	Street lighting	Interior lighting
Good illumination	from 2 to 20	1.2 to 2
Medium illumination	” 20 ” 80	2 ” 4
Weak illumination	” 80 ” 250	4 ” 8

As is evident from the table, with good illumination the nonuniformity inside rooms should be no more than 2 (in passages and on stairways up to 4 is permitted).

When working surfaces are illuminated by individual lamps (local lighting), the walls, ceilings, and floor will be poorly illuminated, and such lighting is usually nonuniform; in view of this, at the present time general lighting is predominantly used, with the aid of a small number of powerful lamps. This is all the more rational because powerful lamps require a smaller expenditure of energy.

Thus from Table No. 30 it is seen that with gas-filled lamps of 50 watts the luminous efficiency is 9.66 lumens, with 200 watts—14.78, and with 1000 watts—19.5 lumens.

Mixed lighting—local and general—is also used.

Example: It is required to illuminate the roller department of a mill, having \(b = 15\) m width, \(l = 27\) m length, and \(H = 4\) m height.

The required luminous flux

\[ F = \frac{K \times E \times S}{\eta} \]

\(K\)—coefficient of reserve; we take \(K = 1.5\)

\(F\)—illumination according to Table No. 29, as the standard for the roller department, 35 l. c. at a height of 1 m from the floor.

\(S = 15 \times 27 = 405\) sq. meters.

We determine the utilization coefficient by first finding the room indices. We choose direct lighting, therefore

\[ \rho_b = \frac{b}{2h} \quad \text{and} \quad \rho_l = \frac{l}{2h}, \]

*) See Korolkov, p. 146.

where \(h\) is the height of the light source above the floor when it is suspended \(0.3\) m from the ceiling, with a room height \(H = 4\) m, and with the illumination standard at a height of \(1\) m from the floor, it will be

\[ h = H - 0.3 - 1.0 = H - 1.3 = 4 - 1.3 = 2.7 \]

\[ \rho_b = \frac{b}{2h} = \frac{15}{2 \times 2.7} = 2.78 \qquad \rho_l = \frac{l}{2h} = \frac{27}{2 \times 2.7} = 5.0 \]

We take the characteristics of the ceiling and walls as average, and from Table No. 31, for the corresponding indices \(\rho_b\) and \(\rho_l\), and for Universal fittings (without a glass shade), we find

\[ \eta_b = 0.56 \qquad \eta_l = 0.59 \]

the utilization coefficient

\[ \eta = \frac{2}{3}\eta_b + \frac{1}{3}\eta_l = 0.57 \]

Then

\[ F = \frac{K \times E \times S}{\eta} = \frac{1.5 + 35 \times 405}{0.57} = 37250 \text{ lm.} \]

We take lamps of 150 watts, which according to Table No. 30 corresponds to 2100 lumens per lamp; we find

\[ \frac{37250}{2100} = 17.7 \]

or 18 lamps.

We distribute them so that, in the passage above the roller mills, instead of 2 lamps of 150 watts, we take 4 lamps of 100 watts (1256 lumens each).

Fig. 42. Arrangement of lamps in the roller-mill room of a mill.

In all, we obtain the energy consumption:

\[ \begin{array}{rcl} 10 \text{ lamps} \times 150 \text{ watts} & \ldots & 1500 \\ 4 \text{ lamps} \times 150 \text{ watts} & \ldots & 400 \\ \hline & & 1900 \text{ watts,} \end{array} \]

or per \(1\ \text{m}^2\) of floor area

\[ \frac{1900}{27 \times 15} = \frac{1900}{405} = 4.7 \text{ watts,} \]

or more than two times less than according to the American standards (10.76 watts per \(1\ \text{m}^2\) of floor area; see below).

Approximate calculation of energy consumption for mill lighting.

In addition to determining the energy consumption for lighting a mill by drawing up, as indicated above, a mill-lighting design, one may use for this an approximate method, determining the necessary energy consumption from the area of the individual rooms and the energy consumption for them in watts.

Thus the power \(W\), in watts, required for lighting 1 sq. meter of floor surface of a room will be:

\[ W\ \text{watt} = \frac{K \times E}{\eta \times \nu}, \]

where

\[ \begin{aligned} K &= 1.5 &&\text{— reserve coefficient,}\\ E &&&\text{— illumination in lux according to Table No. 28.}\\ \eta &&&\text{— coefficient of utilization of the luminous flux,}\\ &&&\text{chosen according to Table No. 31.}\\ \nu &&&\text{— luminous efficacy of the selected source of}\\ &&&\text{lighting, see Table No. 31.} \end{aligned} \]

Thus, for example, for the roller room, taking

\[ \begin{aligned} K &= 1.5,\\ E &= 35,\\ \eta &= 0.4,\\ \nu &= 15.0. \end{aligned} \]

— We find

\[ W = \frac{K \times E}{\eta \times \nu} = \frac{1.5 \times 35}{0.4 \times 15} = 8.78\ \text{watts per }1\ \text{m}^2. \]

According to American data, for lighting the working departments of a mill, 1 watt is required for each sq. foot of mill floor, or 10.76 watts per square meter. For secondary rooms, such as, for example, grain and flour warehouses, etc., one may take half of this.

Taking an energy consumption for lighting of 7.5 watts per 1 m², and the area of all mill floors according to Kettenbach (p. 16), we obtain the following table compiled by us.

Table No. 32.

Approximate total consumption of electrical energy for mill lighting.

No.	Daily output of the mill, tons of grain	Total area of all mill floors, sq. meters	Required energy, kW	Required energy, hp
	20	700	5.2	7.0
	30	900	6.7	9.0
	50	1510	11.3	14.0
	100	2500	18.8	25.5
	120	3000	22.5	30.0
	150	3500	26.3	36.0
	200	4000	30.0	40.0

Energy consumption for lighting in our mills still lags considerably behind these American standards. Thus, for example, mill No. 209 in the city of Tomsk, with a daily output of about 100 tons, has a floor area of about 3,300 square meters and consumes only 3.85 kW for lighting, instead of 18.8–22.5 kW according to the above American standards, i.e., 5–5.5 times less.

Other mills give similar results. And there is no doubt that we must take all measures for the earliest implementation of the above-mentioned decree of the People’s Commissariat of Labor on improving the lighting of our mills.

Table No. 28.

Illumination standards for milling enterprises according to the mandatory decree of the People’s Commissariat of Labor of the USSR of November 17, 1928, No. 545, with additions, amendments, and elaboration by the Scientific and Technical Council for the flour-milling industry under the People’s Commissariat of Trade of the USSR, agreed with the People’s Commissariat of Trade of the USSR.

PREMISES:

No.	Premises	Illumination standard
1	Transmission room	25 l.c. at the height of the transmission level.
2	Roller room	35 l.c. at a height of 1 m from the floor.
3	Distribution room	25 l.c. at a height of 1 m from the floor.
4	Winnowing room	30 l.c. at a height of 1 m from the floor.
5	Sifting room	30 l.c. at a height of 1 m from the floor.
6	Attic room	20 l.c. at a height of 1 m from the floor.
7	For black cleaning	25 l.c. at a height of 1 m from the floor.
8	For white cleaning	30 l.c. at a height of 1 m from the floor.
9	For the flour-discharging department	35 l.c. at a height of 1 m from the floor.
10	For the electrical shop	60 l.c. at a height of 1 m from the floor.
11	In lavatories, washrooms, and baths	50 l.c. on the floor (in the horizontal plane).
12	In dressing rooms	25 l.c. on the floor (in the horizontal plane).
13	In smoking rooms	20 l.c. on the floor (in the horizontal plane).
14	For workers’ warming rooms	20 l.c. on the floor (in the horizontal plane).
15	Passageways in work premises	10 l.c. on the floor (in the horizontal plane).
16	Passage rooms, entrances and exits, stairways, landings, and other premises inside buildings for the temporary presence or passage of people	8 lux at floor level.
17	Yards, driveways, passages, and roads outside the building in places where the possibility of people being present or moving about is not excluded	2 lux at floor level.

Table No. 29.

I. Lighting and electrical data of lamps.

§ 2. Table of lighting and electrical data for empty lamps.

Nominal voltage, V	Power, nominal, W	Power, minimum allowed, W	Power, maximum allowed, W	Light intensity, nominal, candles	Light intensity, minimum allowed, candles	Light intensity, maximum allowed, candles	Luminous flux, nominal, lumens	Luminous flux, minimum allowed, lumens	Luminous flux, maximum allowed, lumens	Specific power consumption, nominal, W/candle	Specific power consumption, minimum allowed, W/candle	Specific power consumption, maximum allowed, W/candle	Specific light output, nominal, lumens/W	Specific light output, minimum allowed, lumens/W	Specific light output, maximum allowed, lumens/W	Service life, hours	Light intensity at end of service life, candles	Luminous flux at end of service life, lumens
110 and 120	15	12.75	17.25	8.60	7.75	9.45	108	97	119	1.75	1.66	1.84	7.18	6.82	7.54	850	6.9	86.4
110 and 120	25	21.20	28.80	17.30	15.60	19.00	217	196	238	1.45	1.38	1.52	8.65	8.20	9.10	850	13.8	174
110 and 120	50	42.50	57.50	35.70	32.10	39.20	447	403	492	1.40	1.33	1.47	8.97	8.52	9.42	850	28.5	358
200	20	17.0	23.0	11.10	10.00	12.20	139	125	153	1.80	1.71	1.89	6.97	6.62	7.32	850	8.9	111
200	30	25.5	34.5	18.80	16.90	20.70	236	212	260	1.60	1.52	1.60	7.85	7.45	8.25	850	15.0	189
200	50	42.5	57.5	34.50	31.00	38.00	433	390	475	1.45	1.38	1.52	8.65	8.20	9.10	850	27.6	346

Table No. 30. Characteristics of mains and electric incandescent lamps.

Voltage, V	Nominal voltage	Power, permissible limits: minimum	Power, permissible limits: maximum	Luminous intensity, nominal	Luminous intensity, permissible limits: minimum	Luminous intensity, permissible limits: maximum	Luminous flux, nominal	Luminous flux, permissible limits: minimum	Luminous flux, permissible limits: maximum	Specific power consumption, W/candle: nominal	Specific power consumption, W/candle: minimum	Specific power consumption, W/candle: maximum	Luminous efficacy, lumens/watt: nominal	Luminous efficacy, lumens/watt: minimum	Luminous efficacy, lumens/watt: maximum	Lamp life, hours	Luminous intensity at the end of service life, candles	Luminous flux at the end of service life, lumens
100	50*)	43	57	38,5	34	43	484	425	542	1,30	1,14	1,46	9,66	8,50	10,82	800	28,8	363
100	75	54	85	68	60	76	855	752	958	1,10	0,97	1,23	11,41	10,04	12,78	„	51	641
100	100	86	114	100	88	112	1256	1105	1410	1,00	0,88	1,12	12,56	11,05	14,10	—	75	942
100	150	129	171	167	147	187	2100	1850	2350	0,90	0,79	1,01	13,96	12,28	15,64	„	125	1575
100	200	172	228	235	207	263	2950	2500	3300	0,85	0,75	0,95	14,70	13,01	16,45	—	176	2213
100	300	264	336	375	338	413	4710	4250	5200	0,80	0,70	0,90	15,70	13,82	17,58	„	281	3533
100	500	440	560	685	615	750	8600	7750	9450	0,73	0,64	0,82	17,20	15,20	19,30	—	515	6450
100	750	660	840	1070	963	1180	13450	12100	14800	0,70	0,62	0,78	17,94	15,79	20,09	„	800	10088
100	1000	880	1120	1470	1320	1620	18500	16580	20340	0,68	0,60	0,76	18,50	16,30	20,72	„	1100	13850
220	60**)	51	69	37,5	33	42	472	415	529	1,60	1,41	1,79	7,85	6,91	8,79	800	828	354
220	75	64	85	53,5	47	60	670	590	750	1,40	1,23	1,57	8,95	7,87	10,00	„	40	503
220	100	86	114	80	70	80	1005	884	1130	1,25	1,10	1,40	10,05	8,84	11,26	„	60	754
220	150	129	171	136	120	132	1710	1505	1915	1,10	0,97	1,23	11,41	10,04	12,77	„	102	1283
220	200	172	228	200	176	224	2510	2210	2810	1,00	0,88	1,12	12,56	11,05	14,07	„	150	1883
220	300	264	336	326	294	359	4100	3690	4510	0,92	0,81	1,03	13,65	12,01	15,29	„	245	3075
220	500	440	560	602	542	662	7560	6804	8320	0,83	0,73	0,93	15,13	13,31	16,95	„	452	5670
220	750	660	840	975	878	1072	12250	11000	13500	0,77	0,68	0,86	16,31	14,35	18,27	„	730	9188
220	1000	880	1120	1370	1236	1510	17200	15500	18920	0,73	0,64	0,82	17,20	15,20	19,30	„	1030	12900

*) Lamps of this power are included in the standard contrary to the production capacity of hollow lamps with spiral filament.

Table No. 31.
Utilization coefficients for the GET lighting fixtures.

Type of lighting fixture	Room index	Light ceiling, medium walls	Light ceiling, dark walls	Light ceiling, very dark walls	Medium ceiling, medium walls	Medium ceiling, dark walls	Medium ceiling, very dark walls	Dark ceiling, dark walls	Dark ceiling, very dark walls
1) “Universal,” of enameled iron; without glass shade.	0.6	30	26	26	30	26	21	25	21
1) “Universal,” of enameled iron; without glass shade.	0.8	37	34	30	37	33	29	33	29
1) “Universal,” of enameled iron; without glass shade.	1.0	41	38	34	40	37	34	37	34
1) “Universal,” of enameled iron; without glass shade.	1.25	46	42	38	43	41	38	40	37
1) “Universal,” of enameled iron; without glass shade.	1.5	48	44	41	45	43	41	42	40
1) “Universal,” of enameled iron; without glass shade.	2.0	51	49	45	50	48	45	47	45
1) “Universal,” of enameled iron; without glass shade.	2.5	55	52	49	54	51	49	51	49
1) “Universal,” of enameled iron; without glass shade.	3.0	57	54	51	56	53	51	53	51
1) “Universal,” of enameled iron; without glass shade.	4.0	59	57	55	58	57	55	56	54
1) “Universal,” of enameled iron; without glass shade.	5.0	61	59	57	59	58	57	57	56
2) “Universal,” of enameled iron with a shade of frosted glass.	0.6	25	22	18	25	22	18	22	18
2) “Universal,” of enameled iron with a shade of frosted glass.	0.8	32	29	26	32	28	26	28	26
2) “Universal,” of enameled iron with a shade of frosted glass.	1.0	35	32	29	35	31	29	31	29
2) “Universal,” of enameled iron with a shade of frosted glass.	1.25	39	36	32	38	35	32	34	31
2) “Universal,” of enameled iron with a shade of frosted glass.	1.5	41	38	36	40	38	36	37	35
2) “Universal,” of enameled iron with a shade of frosted glass.	2.0	44	42	39	41	42	39	41	39
2) “Universal,” of enameled iron with a shade of frosted glass.	2.5	47	44	42	46	44	42	44	42
2) “Universal,” of enameled iron with a shade of frosted glass.	3.0	49	46	45	47	46	45	46	45
2) “Universal,” of enameled iron with a shade of frosted glass.	4.0	50	48	46	49	48	46	47	46
2) “Universal,” of enameled iron with a shade of frosted glass.	5.0	51	50	48	50	50	48	49	48
3) “Lucetta,” for predominantly reflected light. Upper glass frosted, lower glass opal.	0.6	17	13	10	14	11	8	8	7
3) “Lucetta,” for predominantly reflected light. Upper glass frosted, lower glass opal.	0.8	20	17	14	18	14	11	11	9
3) “Lucetta,” for predominantly reflected light. Upper glass frosted, lower glass opal.	1.0	24	20	17	20	17	14	13	11
3) “Lucetta,” for predominantly reflected light. Upper glass frosted, lower glass opal.	1.25	28	23	20	23	19	17	15	13
3) “Lucetta,” for predominantly reflected light. Upper glass frosted, lower glass opal.	1.5	30	26	23	25	20	19	17	15

Type of lighting fixture	Room index	Light: medium	Light: dark	Light: very dark	Medium: medium	Medium: dark	Medium: very dark	Dark: dark	Dark: very dark
	2.0	35	30	27	28	25	22	19	18
	2.5	38	33	29	31	28	24	22	20
	3.0	40	35	33	32	30	26	23	21
	4.0	45	40	37	37	33	31	26	24
	5.0	48	42	39	39	35	33	27	26
4) “Lucetta” for predominantly directed light. Upper glass milky, lower glass matte.	0.6	21	16	13	19	16	15	13	13
4) “Lucetta” for predominantly directed light. Upper glass milky, lower glass matte.	0.8	25	21	18	23	22	20	18	16
4) “Lucetta” for predominantly directed light. Upper glass milky, lower glass matte.	1.0	29	24	22	26	24	22	21	18
4) “Lucetta” for predominantly directed light. Upper glass milky, lower glass matte.	1.25	33	28	24	29	27	25	23	21
4) “Lucetta” for predominantly directed light. Upper glass milky, lower glass matte.	1.5	36	31	27	32	29	28	25	23
4) “Lucetta” for predominantly directed light. Upper glass milky, lower glass matte.	2.0	39	36	31	36	33	32	29	26
4) “Lucetta” for predominantly directed light. Upper glass milky, lower glass matte.	2.5	43	38	35	38	37	35	32	29
4) “Lucetta” for predominantly directed light. Upper glass milky, lower glass matte.	3.0	46	42	37	40	38	37	34	31
4) “Lucetta” for predominantly directed light. Upper glass milky, lower glass matte.	4.0	50	45	41	44	41	40	36	34
4) “Lucetta” for predominantly directed light. Upper glass milky, lower glass matte.	5.0	52	48	44	46	43	42	38	36
5) “Bilux,” double shade. Enameled iron.	0.6	27	23	21	26	23	21	23	21
5) “Bilux,” double shade. Enameled iron.	0.8	32	30	28	29	29	27	29	27
5) “Bilux,” double shade. Enameled iron.	1.0	35	33	31	33	33	31	33	31
5) “Bilux,” double shade. Enameled iron.	1.25	38	36	34	36	36	34	35	34
5) “Bilux,” double shade. Enameled iron.	1.5	40	38	36	37	37	36	37	36
5) “Bilux,” double shade. Enameled iron.	2.0	43	21	39	41	41	39	40	39
5) “Bilux,” double shade. Enameled iron.	2.5	46	44	42	43	43	42	43	42
5) “Bilux,” double shade. Enameled iron.	3.0	47	45	43	44	44	43	44	43
5) “Bilux,” double shade. Enameled iron.	4.0	49	47	46	46	46	45	46	45
5) “Bilux,” double shade. Enameled iron.	5.0	50	48	47	47	47	46	47	46

Lighting fixture type	Ceiling height (index) room	Light: medium	Light: dark	Light: very dark	Medium: medium	Medium: dark	Medium: very dark	Dark: dark	Dark: very dark
6) Iron enameled fixture for directed light for damp places, with light-diffusing glass (type No. 1229a) (Price list LET No. 11, 1925)	0,6	22	17	14	22	17	14	17	14
6) Iron enameled fixture for directed light for damp places, with light-diffusing glass (type No. 1229a) (Price list LET No. 11, 1925)	0,8	28	23	20	27	23	19	23	19
6) Iron enameled fixture for directed light for damp places, with light-diffusing glass (type No. 1229a) (Price list LET No. 11, 1925)	1,0	31	26	23	31	26	23	26	23
6) Iron enameled fixture for directed light for damp places, with light-diffusing glass (type No. 1229a) (Price list LET No. 11, 1925)	1,25	34	30	26	33	29	26	29	26
6) Iron enameled fixture for directed light for damp places, with light-diffusing glass (type No. 1229a) (Price list LET No. 11, 1925)	1,5	36	32	29	36	32	28	31	28
6) Iron enameled fixture for directed light for damp places, with light-diffusing glass (type No. 1229a) (Price list LET No. 11, 1925)	2,0	41	37	33	40	36	33	35	32
6) Iron enameled fixture for directed light for damp places, with light-diffusing glass (type No. 1229a) (Price list LET No. 11, 1925)	2,5	44	41	37	43	40	37	39	36
6) Iron enameled fixture for directed light for damp places, with light-diffusing glass (type No. 1229a) (Price list LET No. 11, 1925)	3,0	47	43	39	45	42	39	41	39
6) Iron enameled fixture for directed light for damp places, with light-diffusing glass (type No. 1229a) (Price list LET No. 11, 1925)	4,0	50	47	43	48	45	43	44	42
6) Iron enameled fixture for directed light for damp places, with light-diffusing glass (type No. 1229a) (Price list LET No. 11, 1925)	5,0	52	49	45	50	47	44	46	44
7) Semi-indirect lighting fixture of type No. 1229, but without reflector. (Same price list.)	0,6	15	13	10	11	10	9	8	7
7) Semi-indirect lighting fixture of type No. 1229, but without reflector. (Same price list.)	0,8	18	15	14	15	13	11	10	9
7) Semi-indirect lighting fixture of type No. 1229, but without reflector. (Same price list.)	1,0	20	18	16	16	15	13	11	10
7) Semi-indirect lighting fixture of type No. 1229, but without reflector. (Same price list.)	1,25	23	20	18	18	17	15	12	12
7) Semi-indirect lighting fixture of type No. 1229, but without reflector. (Same price list.)	1,5	25	23	20	20	18	16	14	14
7) Semi-indirect lighting fixture of type No. 1229, but without reflector. (Same price list.)	2,0	27	25	24	23	20	18	15	14
7) Semi-indirect lighting fixture of type No. 1229, but without reflector. (Same price list.)	2,5	30	27	26	24	23	21	16	15
7) Semi-indirect lighting fixture of type No. 1229, but without reflector. (Same price list.)	3,0	32	29	28	25	24	22	17	15
7) Semi-indirect lighting fixture of type No. 1229, but without reflector. (Same price list.)	4,0	35	32	31	28	25	24	18	17
7) Semi-indirect lighting fixture of type No. 1229, but without reflector. (Same price list.)	5,0	37	34	32	29	28	25	20	19
8) Deep-radiation fixture for high rooms.	For ordinary medium conditions	35–45

Utilization coefficient. In %

Ceiling and wall characteristics

Note. Light walls and ceilings are taken to mean those whose reflection coefficient is more than 50%; medium, from 30 to 50%; dark, from 10 to 30%; and very dark, below 10%.

CHAPTER V.

Economic Foundations of the Electrification of Mills,

The significance of the economic factor. The type of engines currently used in the flour-milling industry. The cost of energy at mills. Examples and data on the cost of energy. Determination of the cost of energy per 1 ton of output. The cost of electric motors and equipment.

“Reduction of cost is the principal task of economic policy.”

The Significance of the Economic Factor.

The economic factor, as is known, usually has predominant importance, and it is understandable that the electrification of mills can develop broadly only under the condition of its economic profitability.

The wide spread of mill electrification in America (in the U.S.A. half of all mills have already been electrified), where everything is, above all, evaluated from the economic point of view, and the calculations given by us below of the profitability of using electric energy at mills, give confidence that, being economically advantageous, the electrification of mills in our own USSR, in connection with the electrification of the entire country, will in the near future assume the broadest dimensions.

Since the expenditure for setting a mill in motion constitutes one of the main parts of the cost of milling, and this expenditure depends on the kind of engines used, it is of no small interest to present here data on the type of engines currently used in the flour-milling industry of the USSR.

The Type of Engines Currently Used in the Flour-Milling Industry.

Whereas in the U.S.A., as has already been noted more than once, more than half of all mills are driven by electricity, in our Union, as may be seen from Table No. 33, the predominant engines in the flour-milling industry (commercial flour mills) are steam engines (47%), and among them the most imperfect at the present time are steam engines proper (39.1%). They are followed by internal-combustion engines (37.2%) and then water engines (15.8%).

Table No. 33.

Composition of primary engines*) in the flour-milling and entire factory-plant industry of the USSR.

Type of engines	Flour-milling industry of the USSR — Number of engines	Flour-milling industry of the USSR — Power in e.h.p.: All engines	Flour-milling industry of the USSR — Power in e.h.p.: Potential	Flour-milling industry of the USSR — Power in e.h.p.: Average actual	Flour-milling industry of the USSR — As % of total industrial total	As % of total mechanical engines of the given industry	All industry — Number of engines	All industry — Power in e.h.p.: All engines	All industry — Power in e.h.p.: Potential	All industry — Power in e.h.p.: Average actual
1. Steam engines	583	83918	67473	55023	7.3	39,1	11072	116931	892031	716005
2. Steam turbines	9	648	628	558	0,1	0,4	520	596656	490945	301205
3. Locomobiles	246	15529	12884	11092	13,4	7.5	3085	119165	96022	80695
	838	100095			20,8	47,0	14677	1885139
4. Diesels	274	33359	29936	26338	17,1	17,3	1340	199563	174588	133597
5. Other internal-combustion engines	686	38993	34381	30672	14,5	19.9	4414	301455	237538	196603
	960	72352			32,06	37,2	5754	501018
6. Water turbines	500	26678	22772	19780	39,6	13,2	1062	78768	65839	51103
7. Water wheels	487	5164	4645	3986	71,0	2,0	590	7477	6539	5401
	987	31841				15,8	1652	86245
Total primary engines: a) number	2785	—	—	—	—	—	22083	2472402	—	—
b) power, e.h.p.	—	204288		—	—	—	—	2471402	—	—
In operating plants. A) All engines. a) Number	2634	—	—	—	—	—	21001	—	—	—
b) Power, e.h.p.	188320	—	—	—	—	—	2375512	—	—	—
B) Operating engines. a) potential power	172548		—		—	—	1990645	—	—	—
b) average actual	151405	—	—	—	—	—	1483942	—	--	---

Cost of energy in mills.

The cost of energy, as we have already noted, constitutes a significant part of the cost of milling; therefore, a reduction in the cost of energy is one of the foundations for reducing the cost of milling.

It must be noted that, as was established at the conference held in America in January 1926 (Harza’s report), the cost of energy is usually made up of:

a) in steam installations, 55–64% from the cost of fuel, and
b) in hydro-power installations, 75–97% from interest on capital.

*) From Table 3A and Table 5A.

It is therefore clear what role in the cost of energy is played by the cost and consumption of fuel in steam installations and the capital outlays for the construction of hydraulic-power installations.

The consumption of fuel, depending on the cost and types of engines employed, thus predetermines the prime cost of energy, and consequently also the prime cost of milling. Taking this into account, we present a number of data on fuel consumption, taken by us from the experience of the operation of mills in the USSR.

Fuel consumption at flat-grinding mills*).

At the time when ordinary double-expansion steam engines with condensation and steam boilers without superheaters were used, the consumption of 12-vershok birch firewood at flat-grinding mills was up to \(4 \tfrac{1}{2}\)—5 sazhen per 1000 poods of grinding**) or 0.693—0.771 cubic meters per 1 ton; with the recent use of locomobiles with higher steam pressure and superheating, fuel consumption has been reduced to only \(1 \tfrac{1}{2}\) sazhen per 1000 poods of grinding, or 0.288 cubic meter per 1 ton.

For oil engines the average consumption is 1 f. (0.410 kg) per horsepower-hour, or 16.7 kg per 1 ton of grinding.

Fuel consumption at high-grade milling mills.

Fuel consumption at high-grade milling mills with double-expansion steam engines without steam superheating is 1.3—1.6 cubic sazhen of birch firewood per grind (1200 poods), or from 0.645 to 0.792 cubic meter per 1 ton of grain milled. With modern steam engines (or locomobiles) of high pressure with steam superheating and condensation, it is 0.58 cubic sazhen per 1000 poods, or 0.287 cubic meter per 1 ton, or 0.6 kg of coal (7500 calories) per 1 effective horsepower-hour (46.2 kg per 1 ton of milled grain).

The total fuel consumption of the entire flour-milling industry of the USSR (commercial mills), in tons (7000 calories), in 1926 was expressed as follows***).

In power installations

192457.3 tons for 10,082.0 thousand rubles.

For technical and economic needs

45479.4 tons 900.9 thousand rubles.

Total . 537936.7 tons
10982.9 thousand rubles.

The average capacity of primary engines was 110 h.p. per industrial establishment for mills, and 233 for the entire industry of the USSR.

) According to the author’s data.
) For example, a mill with 4 runs of stones, \(7/4\) arshins, grinding 1000—1500 poods, burns 6—7 sazhen of birch, 12-vershok firewood.
**) According to the data of the collection.

Cost of Energy

At one time, the Administration for the Study and Utilization of the Water Power of Siberia (Sibispolvod),* headed by the author, investigated the cost of various types of energy for Siberia.

It was found that, when comparing a 4,000-horsepower installation, the cost of 1 effective horsepower per year, for average Siberian conditions, would be:

\[ \begin{aligned} \text{For } 1) \text{ a steam installation} &\ .\ .\ 127\ \text{rub.}\\ 2) \text{ a gas-generator installation} &\ .\ .\ .\ 137\ \text{rub.}\\ 3) \text{ a water-power installation} &\ .\ .\ .\ .\ .\ 49\ \text{rub.} \end{aligned} \]

Taking the annual utilization factor for a mill as 80%, the cost of 1 kW-hour is determined as:

\[ \text{Steam } \frac{12700 \cdot 1.36}{365 \cdot 0.8 \cdot 24} = \text{kop.} — 2.46\ \text{k.} \]

\[ \text{Gas-generator } \ .\ = \text{kop.} — 2.65\ \text{k.} \]

\[ \text{Water-power } \ .\ .\ .\ = \text{kop.} — 0.91\ \text{k.} \]

From this it is evident that hydroelectric energy, under the conditions given, is considerably cheaper.

As calculations show, the cost price of energy for commercial mills in the USSR at the present time is from 2.25 to 3.5 kopecks per kWh.

Table No. 26 gives our calculation of the cost price of energy for the Tomsk State Mills Nos. 208 and 209. From the calculation it is evident that here, with steam engines,** energy costs from 3.17 k. to 3.69 k., on average 3.43 kop. At a commercial mill in Vladivostok with a horizontal steam engine of 427 hp and a vertical one of 60 hp, operating on brown coal, energy costs 2.75 kop.

At a mill in one of the cities of Western Siberia, with a daily output of 71 tons, using a Wolf locomotive of 236 hp (hard-coal consumption 0.65 kg per 1 effective hp per hour), the cost of energy is 2.72 kop. per kWh.

From this it is evident that the electrification of mills in the USSR at the present time can be advantageous only if the supplied energy costs no more than 2.5–3.0 kop. per kWh, which was also noted in the resolution of the Plenum of the Scientific and Technical Council for the flour-milling industry under the People’s Commissariat of Internal Trade (held in Moscow from 6 to 13/VI 1929), on the author’s report “Electrification of Mills,” in point 4 of which it is said:

* See the bulletins of Sibispolvod.
** At Mill No. 208 the steam engine is by Bromley; at Mill No. 209, by the Belgian works.

Table No. 34.

Cost of energy at the Tomsk State Mills Nos. 208 and 209 for the 1927–28 operating year.

No.	Expense item	Mill No. 208: Quantity	Mill No. 208: Cost, rub.	Mill No. 208: %	Mill No. 209: Quantity	Mill No. 209: Cost, rub.	Mill No. 209: %
1	FUEL.
	Fuel consumption (hard coal)	1745 tons			2530 tons
	Cost of fuel at 97.5 kopecks per ton of grain		20700	50.0		30000	61.0
2	LUBRICATION at 9.88 kopecks per 1 ton processed		2555			2555
3	LABOR.
	Engineer	1×135×12	1620		1×135×12	1620
	Assistants	3×68×12	2448		3×62×12	1884
	Oilers	3×38×12	1368		3×45×12	2160
	Firemen	4×35×12	1680		4×50×12	2400
	Coal loaders	8×35×12	840		1×40×12	480
			7956			8544
	For 1 month of vacation, 1:13		612			657
4	Insurance, work clothing, etc., 15%		1178			1281
5	Bonus for coal savings		1468			1567
6	Administration—5%		383			427
7	Repairs, 3% of cost	6000	1800		70000	2100
8	Depreciation, reckoning 20 years—5%		3000			3500
9	% on capital structures: 6%		3600			4200
10	% on capital expenditures for fuel (1 ton, 11.82 = 19.4 kopecks per pood), 6%	685 tons			685 tons
		8250	495		8250	495
11	Insurance of structures against fire, 1% of	60000	600		70000	700

No.	Expense item	Mill No. 208: Quantity	Mill No. 208: Cost, rub.	Mill No. 208: %	Mill No. 209: Quantity	Mill No. 209: Cost, rub.	Mill No. 209: %
12	Number of working days	236	64.65%		260	71.53%
13	Grain processed, tons	21176.6			30619.0
14	Grain dried, tons	—			66631.13
15	Daily capacity, tons	89.5			118.0
16	Required power of steam engines, reckoning 320 h.p. per 100 tons of grain milled per day	287			377
	Addition for the dryer				24 h.p.:3=8
	Reckoning operation at 1:3 of the year	287			385 h.p.
	Power in kW	212			283
	Produced per year, kW-hours	236.212.24	1200768		260.283.24	1765.920
	Cost of a kW-hour	$\dfrac{44347}{1200768}$	3.69 kop.		$\dfrac{56026}{1765920}$	3.17 kop.
	Consumption of hard coal per 1 kW-hour	$\dfrac{1745000}{1200768}$	1.45 kg		$\dfrac{2530000}{1765920}$	1.43 kg
	Per 1 h.p.-hour		1.07 kg			1.05 kg
	Cost of energy per 1 ton of grain milled	$\dfrac{44347}{21176.6}$	2 rub. 09 kop.		$\dfrac{56026}{31260}$	1 rub. 79 kop.
	(For mill No. 209 the production was increased by the amount of dried grain, $30619.0 \cdot \dfrac{385}{377}$)

“Noting that the electrification of mills is profitable only on the condition that electrification will cost no more than another motive power and that the supply of electric power to them will not exceed its cost price to mills at the present time—2.5–3.0 kopecks per kW-hour—one must insist on the establishment of appropriate tariffs by central electric stations.”

Meanwhile, our Central Electric Stations still maintain excessively high tariffs for electricity, making these enterprises, unfortunately, often sources of municipal and other revenues to the detriment of the development of electrification.

Thus, for example, as far as we know, the C.E.S. for the city of Tomsk has set, according to the General Plan, the following prices for the nearest five-year periods.

Price of electric energy per 1 kW	1st five-year period	2nd five-year period	3rd five-year period
For industry	10	6	3
For lighting	35	14.7	9.5—6

Obviously, in order to make it possible to use electric energy for mills, the planned prices must be shifted forward and, already for the coming five-year period, a tariff of no more than 3.0 kopecks per kWh must be adopted.

It is also quite evidently rational to introduce, for electric power released by power stations for mills, differential tariffs that decrease as the demand for energy increases.

According to M. Bell’s data*) with an energy consumption for grinding 1 barrel of grain at the commercial mills of Minneapolis in the USA, from 6 to 7.5 kWh are expended, or 52—65 kWh per 1 ton of grain. With the cost of energy there at ½ cent = 1 kopeck per kWh, we obtain a charge for energy at the Minneapolis mills per 1 ton of 52—65 kopecks. For most other cities (e.g. Kansas), the cost of energy is about 1—1.1 cents (2—2.9 kopecks) per 1 kWh, which already gives a charge for energy of 1 ruble 14 kopecks to 1 ruble 43 kopecks per 1 ton of milled grain.

Ya. Kuprits**) gives data for a mill in the Kansas district of the USA, processing 32 tons of grain per day and operating on a diesel engine (with fuel costing 1.4 dollars per barrel—7 kopecks per gallon): the cost of energy is 1 ruble 60 kopecks per ton, with 49.41% of the expenditure falling on service personnel, 25% on fuel, and 25% on other expenses.

For larger mills of greater capacity, this cost, according to Kuprits’s data, decreases by 20—30%, reaching even, in exceptional cases, 1.00 ruble per 1 ton of grinding.

The cost of electric energy, according to data of the Kansas Power Light Co., with a consumption of 60 kWh per ton and a cost of 1.001 cents per kWh (2.202 kopecks), amounts to 1 ruble 10 kopecks per ton without service and depreciation, and to 1 ruble 43 kopecks with these expenses added (30%).

For a mill with a daily capacity of 308 tons, operating with a utilization factor of 80% (574 hours per month out of 720), with an energy consumption of 60 kWh per ton including elevator operations, energy costs 1 ruble 86 kopecks per ton; of this, 75% consists of payment for energy and 5% of heating, servicing (1 worker), depreciation, and % on capital (from 25,000 dollars). Of interest here is the differential tariff paid by this mill. For the first 120 hours of operation (during the month) it pays 2.3 kopecks (1.15 cents), for the second 120 hours 1.19 kopecks, and for the remaining time 1.5 kopecks per kWh.

According to statistical data of the U.S. Department, the cost of energy in 1925 per 1 ton of processed grain was on average the cheapest for hydraulic-power installations (1 ruble 30 kopecks per ton); next came diesels, electric motors, and the most expensive was for steam engines.

) M. Bell, Power in the Flour Mills at Minneapolis
) Ya. Kuprits. Rationalization of Flour-Milling Production*, pp. 189–192.

From the data presented it is evident that the cost of electric energy for mills in the U.S.S.R. is not very high, amounting to only from 1 to 2.5 kopecks per kWh, which in part explains the undoubtedly rapid development of mill electrification there.

Determination of the Cost of Energy per 1 Ton of Mill Capacity When Electrifying It

The significance of the economic factor has already been noted above, and a number of data have been given on the cost of energy for mills with mechanical drive and for electrified mills.

Here we propose to present an empirical method for determining the cost of energy when electrifying a mill.

The cost of energy of an electrified mill per 1 ton of its capacity is made up of the following principal parts:

1) interest on capital and amortization of all electrical equipment.

2) expenses for maintenance personnel.

3) payment for electric energy.

4) in addition, the cost of energy per 1 ton depends on the utilization factor of the electrical power equipment.

In order to determine the percentage on capital and amortization of all the mill’s electrical equipment, it is necessary to determine its cost. It is clear that, in order to compile an exact cost of the mill’s electrical equipment, it is necessary to prepare an exact design and estimate.

But it is often necessary to give a preliminary general consideration of the approximate cost of electrifying a mill. The methods for these general considerations are what we present here. Since, apart from the wiring from the central station and transformers, the expenses for which are usually borne by the power station itself, the main expense in the mill for electrical equipment is the cost of electric motors, auxiliary devices, and internal wiring, for preliminary calculations the cost of electric motors may be taken as the basis.

Above we have given data on the cost of electric motors from the GET works (see Fig. 29).

In the book Taschenbuch des Müllers for 1927 (the miller’s handbook), published in Germany by the “Miag” association of a number of the largest mill-construction plants, curves are given for the cost of 1 horsepower of alternating-current electric motors (for direct current, 20% more expensive)*) at various powers and various numbers of revolutions (see Fig. 43).

Having selected, according to the data we have given above, the type, power, and number of electric motors for the mill to be electrified, and using these curves, and adding 20% for the expenses of acquiring and installing auxiliary devices and internal wiring, the approximate cost of the installation is determined.

If the wiring from the central power station and the step-down transformers are installed at the expense of the mill, then, of course, their cost must also be taken into account.

*) The cost of electric motors for our average conditions in the U.S.S.R. may be taken (1929) according to the data given above by us for electric motors of the GET works.

Fig. 43. Cost curves for 1 horsepower of electric motors.

In order, when transmitting energy by alternating current over considerable distances, to reduce the cost of conductors, it is rational and advantageous to carry out transmission at the higher voltage the greater this distance is.

Fig. 43 shows a curve, borrowed by us from Ruchmot & Loff, depicting the dependence of voltage in volts on distance.

Thus, for example, if a mill is located 50 km from the central electric station, then according to this curve transmission at a voltage of 35,000 volts will be rational.

Having determined the cost of the electrical equipment, it is then possible to calculate the percentage on capital (usually 6% per annum) and the amortization of the installation (usually 20 years, or 5% per annum).

The expense for maintenance may be taken either according to a preliminary estimate for the operating personnel, or approximately as 1.5% of the cost of all expenditures for electrification of the mill.

Fig. 44. Dependence of current voltage on distance in the transmission of energy by electricity.

The third component of the expenses for energy is the cost of the electrical energy itself, obtained from the central electric station. This cost varies and depends on the tariff per 1 kW-hour.

It is also clear that the cost of energy for an electrified mill per 1 ton of its output depends on the utilization coefficient of its power equipment, i.e., on the ratio of the actual—

... hours actually used in those years, in kWh, to the maximum kWh which could be used with continuous operation of the mill at the maximum load of the electric motors.

While for mills in America (according to Bell et al.) the utilization factor is about 80%, in the USSR it is still low, amounting, for example, even with 250 working days per year, to only 68.5%.

It is also clear that, when calculating energy expenditure, one must take into account the efficiency factor of the electric motors, etc., and the variation of the tariff with energy consumption, if it is differential.

EXAMPLE. Suppose it is necessary to determine the cost of energy per 1 ton of grain milled at a commercial high-grade flour mill with an output of 200 tons per day, with a utilization factor of 80%, and with the cost of energy at 3 kopecks per 1 kWh; the wiring to the mill is at the expense of the Central Electric Station.

According to Table 21, we find the total required power of the electric motors to be 620 h.p., which we distribute as follows:

For the grain-cleaning department, 22%—1 electric motor of 136 h.p.

rollers, sifters—plansifters, 70%—2 electric motors of 217 h.p. each.

remaining machines—8%—3 electric motors of 16.7 h.p. each.

According to the above data on the choice of types of electric motors, number of revolutions, and the quoted data for GET electric motors, we select:

1) For the grain-cleaning department, an open-type electric motor “D” for 3000 volts and \(n = 450\) revolutions per minute, of 150 h.p., with pulley, rheostat, and slide rails . . . . . . . 5150 rubles.

2) For the rollers, sifters, and plansifters at the drive, two open-type electric motors “D” for 3000 volts at \(n = 375\) (direct connection with the shaft), at 10,225 each . . . . . 20450 rubles.

3) Electric motors for the remaining machines, enclosed type PRV—164 s. of 19.7 h.p. each, 500 volts, at 1000 rev. per min., with rheostats, pulleys, and slide rails—3 at 1655 rubles each . . . . 4965 rubles.

Total . . .	30555 rubles

The cost of auxiliary devices (distribution panels, boxes, internal wiring, etc., 20% of the cost) . . . . . . . . . . . . . . . . . . . . . 6112 rubles.

And in all	36677 rubles

Then the annual expenditure on energy will be:

1) % on capital of 36677 rubles at 6% per annum . . . .	2138 rubles
2) amortization, 5% of 36677 . . . . . . . . . . .	1833 rubles
3) servicing, 1.5% of 36677 . . . . . . . . . . .	550 rubles
	4521 rubles

4) Payment for electric power

* See the table of their cost at the end of the book.

The consumption of electric power, with a motor efficiency coefficient \(\eta = 0.9\), will be

\[ N=\frac{620}{1.36\cdot 0.9}=507\ \text{kW}. \]

Thus, if the mill operates for \(80\%\) of 365 days, or for 7008 hours during the year, at 3 kopecks per kW-hour, it will amount to

\[ 507 \times 0.03 \times 7008 = 109400 \]

and in all for the year: 110921,

which per 1 ton of grain milled will amount to

\[ \frac{110921}{200 \times 365 \times 0.8} = \frac{110921}{58400} = 1\ \text{r.}\ 89\ \text{k.} \]

This cost, according to the data we have given above, is not high.

CHAPTER VI

Examples of the Electrification of Mills

1. Electrification of mills in America. Examples of the arrangement and power of electric motors and their application. Typical buildings of American mills.
2. Electrification of mills in the USSR. Data on the Dnepropetrovsk, Moscow, Tashkent, and other mills.

Examples of the Electrification of Mills

For a better explanation of the use of electric motors in flour mills for their electrification, we shall give here several examples.

First we shall present a number of examples from foreign practice, and then mills of the USSR.

Electrification of Mills in America

As has already been noted above, in America, in the electrification of mills, the system of a separate group of machines is used, with separate electric motors assigned first of all to individual operations requiring a considerable expenditure of energy.

Thus, in Fig. 45 there is shown a group of four electric motors of 150 h.p. each, directly connected with the transmissions of individual rows of rolls.

Fig. 45. Group of four electric motors of 150 h.p., driving the transmissions of individual rows of rolls.

Such an arrangement of electric motors, directly connected with the transmissions, is very typical for America.

Fig. 46 shows a 300 h.p. electric motor installed on one of the upper floors of a large American mill, driving the bolter transmission. As can be seen here, the principle of direct connection of an electric motor with a group of separate mill machines has been applied.

Fig. 46. A 300 h.p. electric motor connected with the main transmission driving the bolters.

The placement of electric motors near groups of individual mill machines, in equal parts of the mill, considerably reduces the number of separate transmissions, ropes, and belts, and makes the arrangement of the mill machines, transmission mechanisms, etc., more independent and more rational than in mills driven by a single engine.

To make it possible to start, stop, and control them, either special small distribution boards are installed, or at least switches are necessarily arranged in the appropriate places, making it possible, when needed, quickly to stop the electric motor of one group or another.

For regulating the operation of individual groups, of all the electric motors installed in the mill and in its auxiliary enterprises (elevator, etc.), a main distribution board is installed (see Fig. 47). Here, by observing the readings of the individual instruments, one can constantly monitor both the operation of all the principal groups of machines and mechanisms and the entire operation of the enterprise as a whole.

It is necessary to note that, in order to make possible compliance in the mill—

Fig. 47. Main distribution board for controlling group installations of electric motors in a mill in America.

...of the greatest cleanliness, which in turn undoubtedly affects both the work and health of the workers, and the operation and longevity of the milling machines; in addition to providing the most energetic ventilation and removing dust from all departments of the mill, the Americans spare no expense on strong lighting and on constructing the floors, walls, and ceilings of its buildings from materials that make the slightest deposits of dust noticeable and make it possible to remove it easily.*)

Fig. 48. General view of the brilliantly lit grinding department of an American mill. The walls are of white Italian marble, the floor of Metlakh tiles, the ceiling of white enamel.

In this respect they go even as far as luxury. Thus, Fig. 48 shows the general interior view of the grinding department of an American mill, the walls of which are faced with white Italian marble, the floor is of Metlakh tiles, and the ceiling of white enamel.

Fig. 50. Electric motor driving (by rope transmission) the elevator of the Allis Chalmers works at a mill in Buffalo, USA.

Fig. 49. Elevator for mill personnel (belt width 12 in.)

*) See the chapter “Energy Consumption for Lighting Mill Buildings.”

Hoisting mechanisms for service personnel, ventilators, exhausters, etc., are usually driven by separate electric motors.

Fig. 49 shows such a hoist, typical for an American mill, and in the following Fig. 50 is shown an electric motor of the well-known large American firm Allis Chalmers (on roller bearings), driving a hoist at the International Milling Co. mill in Buffalo, New York State, U.S.A.

Electric motors are also widely used in America for driving individual auxiliary machines in flour-milling production. In doing so, the Americans, with their characteristic inventiveness, apply original ideas.

Fig. 51. Double American crusher with electric motors on both sides. Rotation of the electric motors in opposite directions increases the relative speed.

Thus, for example, Fig. 51 shows a crusher.

For successful crushing work, a very considerable speed of the working surfaces is required; in view of this, the Americans, in addition to using here electric motors with a large number of revolutions (for example, 3600 r.p.m.), install two electric motors on both sides, rotating in opposite directions, which, of course, increases the relative speed of the working surfaces by another factor of 2.

At one of the mills in the city of Minneapolis in America, a synchronous electric motor is installed on the vertical shaft of a water turbine (see Fig. 52), which can also operate as a generator of electric current.

When there is a shortage of water, the generator operates as a synchronous electric motor, receiving electrical energy from neighboring power stations. When, however, there is sufficient water, the water turbine rotates the rotor and the installation operates as a generator, supplying current to the motors of its own mill or, if they are stopped, to neighboring mills (the switching takes place completely automatically).

It is interesting to note that in America, at mills, in order to use at every moment the most economical type of engines, combined power installations of greater capacity are employed than

requires of a mill. Thus, for example, in Minneapolis there is a mill which normally requires about 14,000 hp, but which has:

1. Water turbine . . . . . . . . . 9,000 hp
2. Steam engine . . . . . . . . . 9,000 hp
3. Electric motors . . . . . . . 12,000 hp

          Or in all . . . 30,000 hp.

i.e., more than twice as much as is necessary. The mill uses the most economical drive, and on occasion even sells surplus energy to neighboring enterprises.

Fig. 52. Synchronous electric motor of 300 hp, 180 revolutions per minute, reversible into a generator.

In Fig. 53 is shown a general view of a typical modern American electrified mill [daily capacity 5,000 barrels of flour, or 430 tons of grain (with an elevator attached), built by Nordayke & Marmon]. The eight-story mill building is striking for its large window area.

In the following figure 53 is shown an American (in Kansas) mill with a capacity of 1,000 barrels, or 115 tons, built by Allis Chalmers, with a capacity of 430 tons.

Fig. 53. General view of a modern American electrified mill.

Fig. 54. General view of an American electrified mill, capacity 116 tons (1000 barrels).

Electrification of Mills in the USSR.

At the present time in the USSR all high-grade milling mills have electric lighting; furthermore, many mills have partial electric transmissions to individual machines, etc.; and, finally, there is a number of electrified mills which are driven exclusively by electric motors.

Among such mills one must name the electrified mills of the Joint-Stock Company “Soyuzkhleb” listed below, which, as may be seen from the table, in the 1928–29 economic year had, out of a total of 531 mills with a total daily productivity of 35,348.2 tons, 10 electrified mills with a total electric-motor power of 4,471.5 h.p. and a total daily productivity of 1,061.2 tons, which amounts to only 3.02% of the total productivity of all mills.

List of electrified mills of the Joint-Stock Company “Soyuzkhleb” *)
for the 1928–1929 economic year.

No.	Location	Motor power	Daily prod., tons
55	Pervomaisk (Golte, South-West)	125	33
92	Kiev	350	98.5
94	Kiev	60	40.0
71	Samara	170	45.0
283	Kazan	16	—
90	Seima M. Kursk Ry.	1400	275
215	Leningrad	2118 kW No. 1 No. 2	170.7 284
3	Chelyabinsk	232.5	55
392	Biisk	--	24
381	Cheremkhovo	—	36
10		4471.5 h.p.	1061.2 tons

There is also an electrified mill in the city of Tashkent.

Electrified mill in the city of Tashkent.

The mill in the city of Tashkent (see Fig. 55) has been electrified by transmission of power from the city central electric station.

The daily productivity of the mill is 150 tons (9000 poods). The power (three-phase current) is transmitted at a voltage of 6000 volts. The total power of all electric motors in the mill and the elevator attached to it is 800 h.p. At full load the mill consumes 600 h.p. per 1 ton (4.0 h.p. per 1 ton of daily output); the no-load running is 360 h.p. (60%).

*) See the list of mills of the Joint-Stock Company “Soyuzkhleb” for 1928–29.

Fig. 55. Electrified mill in the city of Tashkent named after Vorovsky, daily production 150 tons.

The grain-cleaning department is 120 h.p. (20%), the grinding department 480 h.p. (80%).

Elevator motor, 35 h.p.; pump, 6.5 h.p. Machines of the repair workshops, 11 h.p.

The Joint-Stock Company “Soyuzkhleb” is also building electrified mills:

1) Moscow mill, 20 thousand poods of daily output.
2) Kulomzinovskaya mill (near Omsk), 20 thousand poods.
3) Tashkent mill (new), 20 thousand poods.
4) Ashkhabad mill, 12 thousand poods.
5) Dnepropetrovsk mill—20 thousand poods.

These mills are in part already nearing completion, while some are in the construction period.

We give below interesting data concerning the recently constructed electrified graded flour mill of “Soyuzkhleb” in Moscow.

Table No. 34 gives general data on the power (in horsepower) and current voltage of the electric motors installed in the mill (by floors), operating from the Moscow substation. From the table it is evident that in all, 18 motors with a total power of 1568.2 horsepower have been installed in the mill; of these, 1400 h.p. operate at 6600.

Table No. 34

Soyuzkhleb. New grading mill in Moscow. Arrangement of the electric power transmission from the Moscow substation.

Floor	Motor power	Voltage
1st floor	9.3 HP	220
1st floor	9.3 HP	220
1st floor	13.6 HP	220
2nd floor	500 HP	6600
2nd floor	200 HP	6600
2nd floor	200 HP	6600
2nd floor	500 HP	6600
[[unclear: floor not visible]]	25 HP	220
[[unclear: floor not visible]]	25 HP	220
[[unclear: floor not visible]]	13 HP	220
4th floor	no electric motors
5th floor	55.8 HP — 6 electric motors of 9.3 HP each	220
7th floor	13.6 HP	220
8th floor	3 HP	220
Total	1568.2 HP

Fig. 56 shows the plan of the third floor of the mill with the layout of electric-energy transmission.

Fig. 56: Diagram of electric-energy transmission at the Soyuzkhleb mill in Moscow.

In Fig. 57, a diagram of the motor mains at 220.

Inscriptions visible in the diagram:

• 8th fl.
• 7th fl.
• 6th fl.
• 5th fl.
• 4th fl.
• 3rd fl.
• 2nd fl.
• 1st fl.
• No. 1 — 30 kW.
• No. 2 — 13.5 kW.
• No. 3 — 9 kW.
• No. 4 — 3? kW.
• No. 5 — 4? kW.
• No. 6 — 19.5 kW.
• No. 7 — 19.5 kW.
• No. 8 — 9 kW.
• No. 9 — 2? kW.
• 220 V
• Switchboard of the new mill
• 160 kW.
• Switchboard of the elevator
• Elevator substation
• MOGES substation
• 6600/230 V
• 500 kVA
• 6600 V
• Moscow Department
• Soyuzkhleb. New grading mill in Moscow. Diagram of motor mains, 220 V.

Fig. 57. Diagram of the motor mains (220 volts) of the Soyuzkhleb mill in Moscow.

In Fig. 58 is shown the signaling circuit in the mill for 6,600-volt electric motors, so that it would be possible to stop them from any floor.

Fig. 58. Signaling circuit to the 6,600-volt electric motors of the Soyuzkhleb mill in Moscow.

At the new Tashkent mill (daily output 20 thousand poods), 2 electric three-phase motors of 6000 V and 50 cycles, type KLD 375/250, are being installed, each with a capacity of 225 h.p.; \(\mu = 363\). The starting torque is 2.0; the couplings are rigid; three-phase electric motors of 6000 V and 50 cycles, type D 600/175, each with a capacity of 175 h.p.; \(\mu = 585\) revs. per minute; torque 2.3. Transmission from an \(800 \times 480\) mm pulley. In addition, there are several small electric motors.

At the mill in Kulomzino (near Omsk), with a daily output of 20 thousand poods, the following installation is planned:

2 three-phase electric motors of 35 h.p. each for the grinding department, and 2 three-phase electric motors of 175 h.p. each for the grain-cleaning department. The electric motors are of the open type. Belt transmission through 6 floors;

Power will be transmitted from the Omsk Central Electric Station, and the voltage will be stepped down at a special substation.

Thus, the electrification of mills in the USSR is beginning to develop ever more rapidly.

All new large mills are being designed and built almost exclusively as electrified ones.

Chapter VII.

Electrification of Agricultural Mills.

The connection of the electrification of agricultural mills with the electrification of rural localities. Energy consumption, productivity of mill rolls, etc. (the author’s practical data) for agricultural mills: 1) with single-pass (whole-grain) milling and 2) with sifted milling.

Electrification of the Agricultural Mills of the USSR in Connection with the Electrification of Rural Localities.

Agricultural mills for single-pass whole-grain and sifted milling are usually the initial energy base in the rural localities of our vast republic.

Beginning with small peasant water mills serving the smallest districts, and up to substantial, well-equipped mills with sifted and whole-grain milling and with a service radius of up to 150 km, and sometimes more, agricultural mills are those centers around which power engineering and electrification begin to concentrate.

The evolution usually begins with the installation of a dynamo for lighting the mill, followed by the connection of the nearest neighbors—the district committee, reading room, club, etc.

The consumption of electrical energy then develops rapidly; electric motors appear: the connection of an oil mill, electric threshing, and the like. The capacity of the mill installation increases, and before long the enterprise develops into an agricultural central electric station electrifying the nearby district.

Indeed, such a development of rural electrification is quite natural, because the combination, in rural localities, of a flour mill that is always so necessary there with the production of electric power for electrification is undoubtedly rational and advantageous.

Here, thanks to the possibility of regulating, within certain limits, the load both of the mill and of certain consumers, a very advantageous combination is obtained for the rational use of the electrical installation with a more or less constant maximum load.

With the implementation of the plan for electrifying the rural localities of the USSR, in most cases it will be rational to build district central electric stations (to use, for example, the energy of nearby rivers, peat bogs, etc.), with electrification first of all of agricultural mills and other agricultural enterprises, of farming, and of broad electric lighting.

Thanks to the use of alternating current, it becomes possible to transmit electrical energy over considerable distances and to electrify extensive rural districts.

Energy consumption, productivity of millstones, rollers, and other mills of simple and sifted grinding.

In order to make possible the electrification of agricultural mills and the selection of electric motors, we give here the most important data on energy consumption, productivity, number of revolutions, etc., of millstones, rollers, and the like for mills of simple and sifted grinding.

I. Mills of simple grinding (bolting mills).

To determine the productivity, energy consumption, and number of revolutions of millstones of various diameters*), the author, on the basis of many years of practice, has compiled Table No. 35, which may be used as a guide when selecting the power of electric motors for bolting mills.

At the same time, if the normal operation of the millstones is taken into account (for example, for a semerik of 400 poods—6.55 tons per day), then it is better to choose the electric-motor power with a margin of not less than 30%, i.e., instead of 11 h.p. take \(11 \times 1.3 = 14.5\)—15 h.p., going in exceptional cases up to 50%—for forced operation; otherwise, under overload the electric motor will heat up, and with careless handling the winding may even be burned out.

As is evident from the note to Table 35, the normal productivity refers to local millstones and medium-dry grain (with medium-coarse grinding). Forced operation refers to artificial millstones, and, with local ones, to very dry grain.

It is clear that if there are elevators for lifting grain or conveyors, then the power of the electric motors must be increased by the amount necessary to put them in motion. In doing this, having set the quantity of grain per unit time and knowing the height to which it must be lifted in the mill, it is possible to calculate easily this additional power of the electric motor, if the coefficient of efficiency of the elevator is taken as

\[ \eta = 0.5. \]

If there are grain-cleaning machines, scouring machines, or other machines, then an allowance of power must be made for them as well.

Example. Suppose it is necessary to electrify a bolting mill with 3 runs of \(7/4\) arshin, with a separator, a cockle separator, and a scouring machine.

The assumed normal productivity of the runs according to Table No. 35 is 400 poods per day (6.5 tons), or for the whole mill \(400 \times 3 = 1200\) poods. Then the necessary power for the runs is \(11 \times 3 = 33\); increasing by 30%, or \(33 \times 1.3 = 43.0\) h.p. The productivity of the separator, cockle separator, and scouring machine is taken as 500 poods per day. Power is required:

Machine	Power
Separator	1.0
Cockle separator	0.3
Scouring machine	4.7
Total	6.0

Taking 4 elevators (3 for the runs and 1 for cleaning and scouring) with a productivity of 1000 poods per day, or

\[ \frac{1000 \times 4}{24} = 167 \text{ p.} = 2730 \text{ kg. in 1 hour, or} \]

*) As is known, in our country millstones are commonly designated by the number of quarter-arshins.

Table No. 35

Productivity, consumption, and speeds of millstones of various diameters.

Compiled by Eng. S. Balakshin from data of practical experience.

Size of millstones	Diameter, vershoks	Diameter, mm	Normal operation: flour output per hour, kg	Normal operation: flour output per day, tons	Normal operation: flour output per day, poods	Normal operation: required power, hp	Normal operation: number of revolutions per minute	Forced operation: flour output per hour, kg	Forced operation: flour output per day, tons	Forced operation: flour output per day, poods	Forced operation: required power, hp	Forced operation: number of revolutions per minute	Normal spindle diameter, English inches	Normal diameter of the lifting screw, English inches
Pyaterik	20	890	13.61	3.27	200	6	250	20.4	4.90	300	9	280	2¾″	1½″
Shesterik	24	1165	20.4	4.90	300	8	200	30.6	7.37	450	13	220	2¾″	2″
Semerik	28	1245	27.22	6.55	400	11	180	40.8	9.80	600	17	200	3″	2″
Vosmerik	32	1425	34.0	8.18	500	14	160	51.1	12.30	750	22	180	3″	2″
Devyaterik	36	1600	40.8	9.80	600	17	140	61.2	14.70	900	25	160	3½″	2½″

Note. Normal productivity refers to millstones of medium dryness of grain. Forced operation refers to artificially dried grain, and, moreover, to dry grain.

with a lifting height of 10 meters, we find the power required for the elevators.

\[ \frac{P \times H}{3600 \times 75} = \frac{2730 \times 10}{3600 \times 75 \times 0.5} = 0.2\ \text{h.p.} \]

In all, electric-motor power is required:

\[ \begin{array}{lr} \text{for the roller mills} \ldots & 43.0\ \text{h.p.}\\ \text{separator, scourer, etc.} & 6.0\ \text{h.p.}\\ \text{bucket elevator} \ldots & 0.2\ \text{h.p.}\\ \hline & 49.2\ \text{h.p.} \end{array} \]

i.e., it is necessary to install an electric motor of 50–60 h.p., or 2 separate electric motors.

\[ \begin{array}{lr} \text{For the roller mills} \ldots & 45\text{–}50\ \text{h.p.}\\ \text{For the rest} \ldots & 6\text{–}7\ \text{h.p.} \end{array} \]

For transmitting motion to the millstone pairs of rye mills, vertical electric motors can be used successfully.

In Fig. 60 is shown a vertical electric motor of the Allis Chalmers works in America. The lower part of the shaft may be made of such a length that it is possible to mount, for example, 2 pulleys side by side and transmit motion by belts directly to the spindles of two pairs of millstones.

Fig. 59. Vertical electric motor.

2. Mills with bolting (“seyanki”).

For mills with bolting, 1 indicated h.p. is required for each 16.38 kg (1 pood) of daily output of the mill.

Example: taking the most common type of mill with bolting and grain cleaning, a four-roller mill (32″ × 14″), and a millstone of 7/4 arsh. (for grinding bran), i.e., in all 3 passages, and with a capacity, when the charges are not less than 250 kg, we usually have an output of about 700 poods (11,000 kg) per day. Counting 16.38 kg per 1 horsepower per hour, an electric motor is required of

\[ \frac{11000}{24 \cdot 16.38} = 28.2\ \text{h.p.},\ \text{or }30\ \text{indicated h.p.} \]

Here too it is rational to add 30% to the power of the electric motor in case of damp grain, etc.

The author knows an electrified mill with bolting which, with 3 pairs of rollers and millstones, at an output of 12,200 kg (750 poods) per day, actually consumes 31.2 h.p., while at idle running 7.6 h.p. is required, or 24.4%.

CHAPTER VIII

Prospects for the Electrification of Mills

Advantages and disadvantages of electrification. Prospects for electrification.

“Wenn Sie nicht der Spitze nicht nahe kommen,
so liegt die Schuld nicht etwa an den Sternen, sondern
an Ihnen selbst” *).

Advantages and Disadvantages of the Electrification of Mills

The rapid development of the electrification of mills abroad, especially in America, is explained by a whole series of advantages of the electrical transmission and use of energy from large central electric stations, instead of the installation of separate power stations at each mill with mechanical transmission of energy.

These advantages are as follows:

1. A simpler arrangement, eliminating a number of transmissions.
2. Less expenditure on friction in superfluous transmissions.
3. Independence in the placement of machines and better use of space in the mill premises.
4. Better control over the operation of individual machines, departments, and the entire mill as a whole.
5. Smaller capital outlay.
6. No fuel stores and no expenditures on them.
7. A smaller number of service personnel.
8. Greater safety with respect to fire.
9. Less space is required for motors, and the need for constructing a special room falls away.

In Fig. 60 it is clearly seen how much smaller the dimensions of the electric motor are than those of a steam engine of the same power. There are also advantages in requiring fewer personnel, in the absence of concern about fuel, in the smaller floor area, etc.

Among the disadvantages of the electrification of mills may be included:

1. Dependence, in receiving energy, on the central station.

Fig. 60. The figure clearly shows that the dimensions of the electric motor are smaller than the flywheel of a steam engine.

*) “If the greatest results have not been attained by you, then the reason lies not in happiness and not in the stars, but only in yourselves.”

Prospects for the Electrification of Mills

We have already noted above, in sufficient relief, the significance and the technical and economic possibilities of electrification, both in Western countries and here in the USSR.

This question is acquiring especially urgent importance for us in connection with the implementation of the plan for the broad electrification of the entire country.

Undoubtedly, in the coming five-year period all existing high-grinding mills located near central electric stations (which can supply electric power) must be electrified. This is technically rational and economically advantageous.

The power equipment currently existing at high-grinding mills can be transferred to other districts and to other enterprises, or to central power stations of lower capacity.

In designing and building new high-grinding mills, it is undoubtedly necessary to design them from the outset with electric drives. This will simplify, as noted above, the arrangement of the machines, reduce the size of the buildings, and, in the overall plan of mill construction, yield substantial savings both in construction and in the operation of our commercial mills.

It is necessary to link the plan for the electrification of mills with the plan for the development of the flour-milling industry of the USSR in the coming five-year period.

No less attention, undoubtedly, must also be given to the electrification of agricultural mills.

By linking the electrification of agricultural mills with the electrification of rural districts and other branches of agricultural industry (oil production, oil-pressing, groat-crushing, and other industries), one may count on a very broad development of the electrification of agricultural mills in the near future.

The construction of a number of electric power stations in agricultural districts will make possible the broadest electrification of these districts.

CHAPTER IX

Conclusion

The possibility and necessity of electrifying the mills of the USSR in the near future.

“Ne remettez jamais à demain ce que
vous pouvez faire aujourd’hui”*)

Conclusion

The data presented above on the state of mill electrification and its technical and economic foundations show with sufficient clarity what significance electrification has for this largest branch of our industry at the present time, and what brilliant prospects are opening before it in the future.

The United States has already electrified half of all its mills. In our Union we likewise have every possibility for this. And undoubtedly, already in the coming five-year period, the electrification of mills in our country will be carried out on the broadest scale.

We call upon all workers in the flour-milling industry, engineers, and workers of our power stations to do everything so that in the very next years, alongside the electrification of the country, the electrification of our mills may be accomplished on a scale not inferior to that of the Western countries.

The electrification of mills will bring a reduction in the cost of food products; the electrification of mills is the latest achievement of milling technology!

Behind us are the successes already achieved in the electrification of mills—ahead lies a brilliant future.

The Americans say:

“If electrical engineers have perfected transmission of power by wireless, the flour mills will be ready to apply it and to make the first industrial application!”

(If electrical engineers give us wireless transmission of energy, then flour mills are ready to be the first to use this invention for industrial purposes.)

And so, forward, toward the broadest electrification of mills!

Tomsk.
S. Balakshin.

*) “Do not put off until tomorrow what can be done today.”

APPENDIX.

GENERAL DATA AND TABLES.

Table No. 1

For determining the diameters of transmission shafts, given: horsepower and number of revolutions per minute.

Number of revolutions per minute	50	60	70	80	90	100	125	150	175	200	225	250	275	300	325	350	375	400
50	120	130	135	135	140	145	155	160	165	170	175	180	180	—	—	—	—	—
60	115	120	125	130	135	140	145	155	160	165	170	175	180	180	—	—	—	—
70	110	120	120	125	130	135	140	150	155	160	165	170	175	180	180	180	—	—
80	110	115	120	120	125	125	135	145	150	155	155	160	165	170	170	175	180	180
90	105	110	115	120	120	125	135	140	145	150	155	155	160	165	165	170	175	175
100	105	110	110	115	120	120	130	135	140	145	150	155	155	160	165	165	170	170
110	100	105	110	115	115	120	125	130	135	140	145	150	155	155	160	160	165	170
120	100	105	105	110	115	115	125	130	135	140	140	145	150	155	155	160	160	165
130	95	100	105	110	110	115	120	130	130	135	140	145	145	150	155	155	160	160
140	90	100	105	105	110	115	120	125	130	135	135	140	145	145	150	155	155	160
150	95	100	100	105	110	110	115	120	125	130	135	140	140	145	150	150	155	155
160	90	95	100	100	105	110	115	120	125	130	135	135	140	140	145	150	150	155
180	90	95	95	100	105	105	110	115	120	125	130	130	135	140	140	145	145	150
200	85	90	95	95	100	105	110	115	120	120	125	130	130	135	140	140	145	145
225	85	90	90	95	100	100	105	110	115	120	120	125	130	130	135	135	140	140
250	85	85	90	95	95	100	105	110	110	115	120	120	125	130	130	135	135	135
275	80	85	90	90	95	95	100	105	110	115	115	120	120	125	125	130	130	135
300	80	85	85	90	90	95	100	105	105	110	115	115	120	120	125	125	130	130
325	80	80	85	85	90	90	95	100	105	110	110	115	115	120	120	125	125	130
350	75	80	85	85	90	90	95	100	100	105	110	110	115	120	120	120	125	125
375	75	80	80	85	85	90	95	95	100	105	110	110	115	115	120	120	120	125
400	75	75	80	85	85	85	90	95	100	105	105	110	110	115	115	120	120	120

Table No. 2.

Normal speeds of transmission shafts.

(Adopted in German industry.)

Under load, the following speeds should be observed whenever possible:

25	40	63	100	160	250	400	630	1000
28	45	71	112	180	280	450	710	1120
32	50	80	125	200	320	500	800	1250
36	56	90	140	225	360	560	900	1400

Table No. 3.

Normal diameters of transmission shafts.

(Adopted in German industry.)

Diameters in millimeters.

25, 30, 35, 40, 45, 50, 55, 60, 70, 80, 90, 100,
100, 110, 125, 140, 160, 180, 200,
200, 220, 240, 260, 280, 300.

Table No. 4.

Normal pulley sizes for transmissions.

(Adopted in German industry.)

Diameter of the cylindrical or crowned rim of the pulley in millimeters:

50, 63, (±1); 80, 90, 100 (±2);
100, 112, 125, 140, 160, 180, 200, (±2);
225, 250, 280, 320, 360, 400, 450, 500, (±3);
560, 630, 710, 800, 900, 1000, (±5);
1120, 1250, 1400, 1600, 1800, 2000, (±7);
2250, 2500, 2800, 3200, 3600, 4000, (±10);
4500, 5000, 5600, 6300, (±15);
7100, 8000, 9000, 10000, (±20).

The figures in parentheses indicate tolerances in mm.

Table No. 5.

Normal width of transmission pulleys.

(Adopted in German industry.)

Pulley width in millimeters.

40, 50, 60, 70, 85 (−2);
100, 120, 140, (−4); 170, 200, (−6);
200, 230, (−6); 2[[unclear: middle digit]]0, 300, (−8);
300, 350, (−8); 400, 450, 500, 600, (−10).

The figures in parentheses indicate tolerances in millimeters.

Table No. 6.

Specific weights of the principal products of the milling trade.

Kind of product	Weight of 1 m, in kg	Kind of product	Weight of 1 m, in kg
Wheat grain	720 840	Feed rye flour	300—375
Middlings (wheat)	450—550	Rye bran, fine	300—375
Fine groats	350—450	Rye bran, coarse	280—320
Coarse groats	550—650	Barley	600—650
Wheat flour 0—III	550—600	Oats	400—450
Ditto IV—V	300—400	Maize	700—800
Feed wheat flour	300—350	Millet	660—700
Wheat grain husks	200—250	Malt	500—550
Wheat bran	300—350	Fine malt	350—400
Rye	680—750	Rice	650—680
Middlings	500—600	Peas	600—750
Rye flour 0—I	450—550	Sunflower
Rye flour II—IV	300—400

Some data on measures used in the American and English milling industry.

1 English pound (lb or lbs) = 16 ounces = 0.453592 kg.
1 European long ton (long ton) = 2240 lb. = 1.016027 tn.
1 American short ton (short ton) = 2000 lb. = 0.9072 tn.
1 English quarter = 8 bushels = 480 lb. of wheat = 217.72 kg.

1 bushel of wheat . . . 60 lb. . . . 27.21 kg.
1 bushel of rye . . . . . 56 lb. . . . 25.40 kg.
1 bushel of barley . . . 48 lb. . . . 21.77 kg.

1 English sack of flour (sach) = 280 lb. = 127.00 kg.
1 American barrel of flour (barrel) = 196 lb. = 88.9 kg.

Productivity and energy consumption of American and English mills.

Americans (U.S.A.) usually reckon the daily productivity of mills not by grain, as is customary in Europe, but by the flour produced by the mill over the course of 24 hours in barrels (of 196 English pounds = 88.9 kg).

The English also reckon productivity by flour in sacks (Sach) (of 280 English pounds = 127 kg).

Hence it is clear that the productivity of American and English mills cannot be compared with the productivity of European mills without conversion.

In the table below, compiled on the basis of lengthy experiments, the yields of flour (excluding feed flour) are given.

Table No. 7.

Yields of flour at American mills from wheat of various quality.

1. Bushel (U.S.A.) of dry wheat weighs, pounds	50	51	52	53	54	55	56	57	58	59	60	61	62
% yield of good flour (straight flour)	64	66	68	69	71	72	74	75	76	77	77	78	79

If this table is taken as a basis, then with an average wheat weight in America of 60 lb. per bushel, or 78 hectoliters, the average yield of flour will be 77%.

If one wishes, from the daily productivity of a mill according to American data in barrels (Barrel) of flour, to pass to metric sacks (of 100 kg.) of grain, then the number of barrels is multiplied by the ratio

\[ \frac{0.889}{0.77} \]

or, in round numbers, by 1.55. To convert productivity from American barrels of flour into tons of grain, multiply by 0.1155.

Conversely, to convert the productivity of a European mill in sacks (of 100 kg.) of grain into American barrels (with a flour yield of 77%), multiply by 0.87. It is clear that the coefficients given are applicable only with the assumed flour yield of 77%.

Examples. 1. Let the productivity of an American mill be 5000 barrels in 24 hours; then the daily productivity in tons of grain (with a flour yield of 77%) will be

\[ 5000 \times 0.115 = 575 \text{ tons.} \]

1. The productivity of a mill in the USSR is 100 tons of grain (1000 sacks of 100 kg.) per day. What is the productivity in barrels (of flour) according to the American method?

\[ 100 \times 0.87 = 870 \text{ barrels.} \]

To convert the hourly productivity in sacks (of 280 English pounds) of flour of an English mill into the daily productivity in sacks of grain (of 100 kg.) of a European mill, multiply the English “sacks” by

\[ \frac{1.27 \times 24}{0.77} = 39.6 \]

or, in round numbers, by 40.

It is clear that these conversion coefficients are also applicable only with the stated average weight of grain and average yield of flour.

Example 3. The productivity of an English mill is 25 English sacks of flour per hour. Then the productivity in grain is

\[ 25 \times 40 = 1000 \]

sacks of grain in 24 hours, or 100 tons.

Conversion of energy consumption from American measures to the metric system.

To obtain the specific consumption \(N_o\), in metric horsepower, of energy per 1 ton of grain milled at the mill per day, it is necessary to divide the specific consumption \(N_b\), in metric horsepower, per 1 barrel of flour (as is customary in America), by 0.1155, or

\[ N_o = \frac{N_b}{0.1155}. \]

Example. Suppose a mill mills 1000 barrels (of flour) per day, consuming 333 metric hp (or \(N_b = 0.33\)).

Then

\[ \text{Then } N_o = \frac{N_b}{0.1155} = \frac{0.33}{0.1155} = 2.86 \text{ tons of grain per 1 horsepower} \]

in 24 hours.

Table No. 8.

Comparison of the weight of flour in sacks of 100 kg and American barrels of 196 English pounds.

Number of sacks	50	80	100	160	200	250	320	400	500	800
Number of barrels	56.0	89.6	112.0	179.2	224.0	228.0	358.4	448.0	560	896
Number of sacks	1500	1600	2000	3200	4000	5000	8000	10000
Number of barrels	1680	1790	2240	3584	4480	5600	8960	11200

Danger of electric current to humans.

Fatal accidents have occurred at

\[ \begin{aligned} &500 \text{ volts direct current;}\\ &120 \text{ “ alternating current;}\\ &120 \text{ “ three-phase current.} \end{aligned} \]

On average, the current strength required for a fatal shock with alternating current is determined as 0.1 ampere; or, with the resistance of a normal person (through both hands) averaging 20–300000 m, so that to attain a fatal current of 0.1 ampere a voltage of 2–3 thousand volts is required.

SUMMARY

The purpose of this book is to acquaint mill workers, mill engineers, and students with the electrification of flour mills.

First, a general characterization is given of the energy economy of industry in the USSR, illuminating the present state of electrification of flour mills.

Thereafter, on the basis of numerous data from Russian and foreign literature, the consumption and distribution of energy in flour mills of various types are presented. For the first time, the author provides a generalization of these data in the form of tables and diagrams, facilitating the selection of electric power for flour mills.

The book briefly explains the fundamental principles of transmitting electrical energy, gives the characteristics of electric motors of different types, their prices and overall dimensions, and sets forth the basic principles of the construction and design of electric lighting for flour mills.

The author gives economic data on the basic cost and operating cost of various types of motors for mills, an example of mill construction, and the prospects for electrification of flour mills.

SUMMARY

The author of this book sets forth the problem of familiarizing mill workers, engineers, and students with the electrification of mills.

At the beginning, the author gives a general characterization of the energy economy of industry in the USSR, which clarifies the state of electrification of mills.

He then provides a considerable amount of data from Russian and foreign sources concerning the energy consumption of mills of different types and its distribution. Here, for the first time, the author presents conclusions in the form of tables and diagrams, facilitating the choice of electric motor power.

This book presents the fundamental principles of the transmission of electrical energy, characteristic data for electric motors of different types, and their prices and overall dimensions.

It also discusses the construction and design of electric lighting.

The author shows the economic data for the cost of construction and operation of the different types of motors for mills, as well as an example of electrification, its preference, and its prospects.

SUMMARY

The purpose of the book is to acquaint the reader with the application of electrical energy in mills (the electrification of mills), and it is intended for those who work in the milling industry, for engineers, and for students.

At the beginning, the author gives a general characterization of the energy economy of the USSR and the state of electrification of its mills.

Then, on the basis of Russian and foreign sources, numerous data are presented on the application of energy and its distribution among the various types of mills. Here the author gives, for the first time, general conclusions and brings them together in the form of tables and diagrams, which greatly facilitates the selection of electric motors.

The book sets forth the principles of electric power transmission, the design, characteristics, and prices of electric motors of various types, and the principles for arranging and designing electric lighting in mills.

The author also provides economic data on the value of the installation and utilization of various types of prime movers for mills, examples of the electrification of flour mills, and its advantages and prospects.

Literature on the Electrification of Mills

Russian

Kuprits Ya.—Rationalization of flour-milling production—1929, Moscow.

Factory and Plant Industry of the USSR. Issue 2. Construction and operation of power equipment. Energy and fuel balance. Statistical Publishing House of the Central Statistical Administration of the USSR. Moscow, 1929.

Kozmin P. A., prof.—Flour-milling and cereal production. Moscow, 1925.

Notovich S.—The mill mechanic’s companion. Odessa, 1902.

Bulletins of Sibispolvod.

Ugrimov B. and Gentsteller G.—Fundamentals of high-current engineering. Vol. I—direct current and alternating current. Moscow, 1917.

Electrification—journal.

Linde I. V.—engineer. Reference book for electrical engineers. Moscow, 1920.

Croft T.—Electric stations and substations. Moscow.

Gefrer S.—engineer. Alternating-current motors (elementary exposition).

Kholuyanov F. I., prof.—Asynchronous alternating-current motors. State Publishing House. Moscow, 1924.

Bukshtam S.—A flour miller’s handbook, ed. by Prof. M. M. Pokuto. Moscow, 1929.

Soviet Flour Milling and Bread Baking.

Electricity.

Instructions and standards for power installations of mills of the joint-stock company “Soyuzkhleb.” Moscow, 1928.

Uarov G. A., engineer-electrician. Consumption of electrical energy by machines at the mill named after V. I. Lenin. Soviet Miller, 1928, No. 2.

Balakshina E. S., engineer.—Daylighting of industrial buildings. Tomsk, 1928.

Korolkov A. L., prof.—Course in electric lighting. State Publishing House. Moscow, 1929.

Report of the Nizhny Novgorod occupational dispensary on the investigation of lighting in flour mills in Nizhny Novgorod. 1929.

List of mills of the joint-stock company “Soyuzkhleb” for the 1928–29 economic year.

English

The—Consolidated Grain Milling Catalogs 1927–28. Compiled and published by National Miller.

Bell M. D.—Power in the Flour Mills at Minneapolis. Mechanical Engineering, 1928, p. 833.

Ruchmor R. B. and Lof. E. A.—Hydro-Electric Power Station. New York, 1923.

Dedrick B. W., Prof. Practical Milling. Chicago, Ill., M. S. A., 1924.

Standard Handbook for Electrical Engineers. New York, 1922.

Marsh A. M. Floor Mill Power. National Miller, 1929, p. 20.

The Operative Miller.

National Miller. Chicago.

Milling. London.

German

Baumgartner F., Ing.—Handbuch des Mühlenbanes und der Müllerei. Berlin, 1902.

Kattenbach Fr.—Der Müller und der Mühlenbaner. 2nd and 5th editions. Leipzig, 1922.

Weisenmüller R.—Die Müllerei. 2 vols. Vienna, 1925.

Taschenbuch des Müllers—edition 1927. Published by “Miag.”

Muhlen Kalender. 1926.

Blöch L., Dr. Ing.—Lichttechnik. Berlin, 1921.

Die Mühle.

Zeitschrift für das gesamte Mühlenwesen—Frankfurt a/M.

French

De Laharpe.—Notes & Formules de l’ingénieur. Paris.

René Koechlin, Ing.—L’établissement d’usines hydroélectriques. Paris, 1926.

Rogne et Labalétrier.—Manuel pratique de meunerie. Paris, 1891.

La Meunerie Française.

Journal de la Meunerie.

Alphabetical Index

to S. Balakshin’s book Electrification of Mills.

A.

American mills, consumption and distribution of energy . . . 18—24
America, approximate electrification of mills . . . 92—97
Asynchronous motor . . . 40—44

B.

Barrel—energy consumption per barrel . . . 22

V.

Roller mills, energy consumption . . . 16
Transmission shafts . . . 62, 112—113
Specific weights of products of the flour-milling department . . . 114
Grain moisture, coefficient of increase in energy consumption . . . 27
Flour yields of American mills . . . 115

G.

Gas-generator installations, cost of energy . . . 84
Hydraulic-power installations, cost of energy . . . 84
GET—electric motors for mills, types, prices . . . 48—59

D.

Electric motors, see electric motors . . .

E.

Units of light (basic) . . . 67

Zh.

Millstones, productivity, energy consumption . . . 105—107

I.

Change in power when starting a mill . . . 34

K.

Coefficient of utilization of the power apparatus in industry . . . 9
Coefficients of utilization of GET lighting fixtures . . . 78—80
Coefficient for converting energy consumption to conventional grinding . . . 25—26
kWh, energy consumption at merchant mills . . . 32
Housings of electric motors . . . 45—46

L.

Electric lamps, arrangement in a mill . . . 69—75
Leningrad mill, electrification . . . 98
Literature on the electrification of mills . . . 140
Lux . . . 67
Lumen . . . 67

M.

Rye-grinding mills (rye mills) . . . 107
Measures, American and English . . . 114—115
Power required when starting a mill . . . 33—34
Flour-milling industry of the USSR, general description . . . 4

N.

Standard current voltages . . . 37
Shortcomings of electrification . . . 108
Standards of illumination for mills . . . 75

O.

Total power of factory and plant engines in the industry of the USSR . . . 2
General scheme of energy transmission . . . 38
Lighting fixtures . . . 70—72
Mill lighting—calculation . . . 69
Basic units of light . . . 67
Basic diagrams of DC motors . . . 36

Basic indicators of energification and electrification of industry . . . . . 7
Basic formulas of alternating current . . . . . . . . . . 38
Danger of electric current for man . . . . . . . . . . 116

P.

Steam installations, cost of energy . . . . . . . 84–86
Transmission of energy in mills by electricity . . . . . 35–65
Conversion of energy consumption from American measures to the metric system . . . . . 116
Alternating-current motors . . . . . . . . . . 40
Prime movers of the flour-milling and factory-and-works industry of the USSR . . . . . 82
Transmission of motion from electric motors . . . . . 61
Prospects for the electrification of mills . . . . . 108, 109
Transmission of energy in mills by electricity . . . . . 35
Productivity and energy consumption of American and English mills . . . . . 114–115
Advantages of electrification . . . . . . . . . 108
Design of electric lighting for mills . . . . . . 68
Approximate energy consumption for lighting mills . . . . . 32
Various grindings, energy consumption . . . . . 25
Starting a mill, required power . . . . . . . 33
Starting rheostats, see Starting rheostats . . . . . . .
Increase in energy consumption for grinding with increased moisture . . . . . 27
Energy consumption of commercial mills in America . . . . . 22–23
Energy requirement for lighting mills . . . . . 74

R.

Arrangement of lamps in a mill, see arrangement of lamps . . . . . 69–74
Energy consumption (see American mills) . . . . . .
Distribution boxes . . . . . . . . . 55–59
Calculation of mill lighting . . . . . . 69–70
Energy consumption per 1 ton of daily grinding . . . . . 30
Energy consumption by different types of mills . . . . . 10–24
Energy consumption by high-grinding mills . . . . . 31–32
Energy consumption of commercial mills in the USSR . . . . . 23–24–25
Energy consumption in the flour-milling and factory-and-works industry of the USSR . . . . . 6–7
Distribution of energy in mills . . . . . 15–22–33
Sifting mills, energy consumption . . . . . 11
Starting rheostats . . . . . . . . . 55–59

S.

Comparison of the weight of flour in kilograms and American barrels . . . . . 116
Diagrams of asynchronous motors with simple winding . . . . . 40–41
General diagram of energy transmission by electric current . . . . . 37
Diagram of installation of electric motors in a mill . . . . . 60
Diagrams of three-phase electric motors . . . . . 49
Electrification of agricultural mills . . . . . 104–107
Standard voltages of electric current . . . . . 37
Cost of electric motors . . . . . 88–50–56
Cost of 1 horsepower of three-phase electric motors . . . . . 54
Cost of energy . . . . . . . 84–87

T.

Electrification of the Tashkent mill . . . . . 99
Technical bases of mill electrification . . . . . 10
Lean coal . . . . . . . . . 67
Types of mills . . . . . . . . 19
Types of mills, energy consumption and distribution . . . . . 10–11
Types of electric motors . . . . . 35
Commercial mills, energy consumption . . . . . 14–33
Ball-bearing transmissions, energy consumption . . . . . 29–30–31
Three-phase motors . . . . . 50–55–56

U.

Increase in specific energy consumption depending on grain moisture . . . . . 27
Specific energy consumption . . . . . 10–16–26
Increase of specific energy consumption due to moisture . . . . . 27
Installation of electric motors . . . . . 56
Conditional grinding, definition . . . . . 26
Reduction of energy consumption in commercial mills using ball bearings . . . . . 18

F.

Actual average energy consumption by mills . . . . . 29
Basic formulas of alternating current . . . . . 38–39

Kh.

Characteristics of the flour-milling industry of the USSR (general) . . . . . 4
Characteristics of the change in the efficiency coefficient of electric transmission . . . . . 38
Characteristics of alternating-current motors . . . . . 40
Energy economy of industry . . . . . 2

Ts.

Prices of electric motors . . . . 50–56—88

Sh.

Ball bearings in mills, reduction of energy consumption . . . . 18
Pulleys, transmission, normal dimensions . . . . 113

E.

Economic foundations of mill electrification . . . . 81
Electric lighting of mills . . . . 65–80
Electric energy, consumption . . . . 31–32
Electrification of agricultural mills . . . . 104–107
Electrification of mills, prospects . . . . 108–109
Electrification of mills of the USSR . . . . 98–103
Electrification of mills abroad (examples) . . . . 92–97
Electrification of mills, technical foundations . . . . 10
Three-phase-current electric motors . . . . 62
Electric motors of GOELRO plants . . . . 48
Electric motors of the flour-milling industry of the USSR . . . . 5
Direct-current electric motors . . . . 35–37
Alternating-current electric motors . . . . 40
Cost of electric motors (see cost of electric motors) . . . .
Alternating-current electric motors of mills in America . . . . 47
Energy base of industry . . . . 3
Energy economy of industry . . . . 2
Energetics and electrification of industry (basic indicators) . . . . 7
Energy, distribution in mills—see distribution of energy . . . .
Cost price of energy . . . . 82–83
Energy, consumption, see energy consumption . . . . 10
Cost of energy . . . . 84–87
Cost of energy (example) . . . . 90–91

Ya.

Distribution boxes . . . . 55–59

Izvestia of the Siberian Technological Institute
Responsible editor Prof. M. I. Evdokimov-Rokotovsky.