On the Selection of Converters for the Electric Drive of Winches with Automatic Rope Tension Control
Abstract Generated abstract
This paper compares thyristor and electromechanical reversible converters for DC electric drives of winches with autonomous power supply and automatic rope tension control. It evaluates their suitability for low and medium speed tracking operation, frequent reversals, and operation against a stop, considering braking capabilities, control simplicity, response, efficiency, power factor, installed supply power, weight, dimensions, cost, and operating expenses. The authors argue that although thyristor converters offer higher efficiency and faster response, these advantages are not decisive for the winch application, while electromechanical converters provide simpler control, greater braking flexibility, higher overload capacity, lower cost, and more favorable weight and size characteristics. The paper concludes that electromechanical converters are generally the more expedient choice for such winch electric drives.
Full Text
ON THE SELECTION OF CONVERTERS FOR THE ELECTRIC DRIVE OF WINCHES WITH AUTOMATIC ROPE TENSION CONTROL
V. A. BEINAROVICH, V. M. KARPOV, A. D. KOZHUKHOVSKII
(Presented by the scientific and technical seminar of the Scientific Research Institute of Automation and Electromechanics)
In winch mechanisms with autonomous power supply and automatic rope-tension control, the electric drive has a power of 5–25 kW and operates in a tracking mode, with reversal of the motor’s direction of rotation depending on changes in rope tension, predominantly with small displacements of the winch drum and at low and medium speeds. A characteristic operating mode of a winch electric drive is also operation “against a stop.” Under the indicated conditions, for a DC tracking winch electric drive it is expedient to use only thyristor or electromechanical reversible converters. The principal requirements in this case are simplicity, reliability, and minimum weight and dimensions.
A comparative assessment of the technical characteristics of thyristor and electromechanical converters makes it possible to draw the following conclusions. In terms of the range of speed and torque control and starting characteristics, both types of converters satisfy the imposed requirements. In terms of the characteristics of braking modes, electromechanical converters have broader capabilities, providing, in addition to counter-current and regenerative braking, also dynamic braking, which is of great importance in systems with autonomous power supply. Electromechanical converters have a simpler and, consequently, more reliable control device. The response speed of thyristor converters is higher; however, for winch electric drives this is not essential, since the response speed of both types of converters is sufficient.
Thus, thyristor converters in tracking winch electric drives do not offer substantial advantages in technical characteristics, and owing to the simplicity and high overload capacity (“ruggedness” of the system), the use of electromechanical converters should be considered more expedient here.
For a comparative assessment of technical-and-economic indicators, Table 1 gives data for converters intended to operate with identical actuating motors.
The main advantage of thyristor converters is their high efficiency, which is important for high-power installations. The power factors (\(\cos \varphi\)) of both converters in the rated mode are identical. However, in winch electric drives, regul...
regulation of speed is usually carried out at constant torque (current). The nature of the change in the efficiency and \(\cos \varphi\) of converters when operating with a constant rated load current is shown in Fig. 1 [2]. The power factor of a thyristor converter in the continuous-current mode differs almost not at all from \(\cos \varphi\) (the difference is less than 11%) [1, 2].
Table 1
| No. | Characteristics | Thyristor converter | Electric-machine converter |
|---|---|---|---|
| 1 | Converter type | PTTR 230/200 | A2-71-2-P62 |
| 2 | Rated power (kW) | 23 | 30--25 |
| 3 | Total weight of the converter (kg) | 500 | 360 |
| 4 | Efficiency (%) | 97 | 76.5 |
| 5 | Power factor | 0.88 | 0.88 |
| 6 | Overall dimensions | \(630 \times 850 \times 2400\) | \(1290 \times 546 \times 400\) |
| 7 | Cost of the converter (rubles) | 2400 | 860 |
The apparent power \(P_s\), which determines the installed power of the power-supply sources, is, already for a speed-control range greater than \(1:8\), higher for thyristor converters than for electric-machine converters (Fig. 1).
Fig. 1
The weight-and-size characteristics of electric-machine converters are better than those of reversible thyristor transformer converters (Table 1) [1, 3, 4]. In addition, in thyristor electric drives, because of current pulsations, the power, and consequently the weight and dimensions of the motors, are overestimated [1, 2]. The operating costs for thyristor drives are 12--25% lower [6], but their cost is 3--5 times higher than that of electric-machine drives [4, 5].
Thus, for winch electric drives, the use of electric-machine converters should be considered more expedient.
References
-
E. Yu. Danyushevskaya. Reversible thyristor DC electric drives. “Energiya,” 1970.
-
A. A. Bulgakov. Electronic devices for automatic control. Moscow–Leningrad, GEI, 1958.
-
Ya. S. Gurin, M. Ya. Kurochkin. Unified-series DC electrical machines of frame sizes P 1–22 and motor-generators. Catalog-reference book. Moscow, VNIIZM, Department of Scientific and Technical Information, Standardization and Normalization in Electrical Engineering, 1964.
-
Product nomenclature of the Saransk Order of the Red Banner of Labor “Elektrovypryamitel” plant for 1971.
-
Price list No. 15—01. Wholesale prices for medium- and low-power electrical machines. Moscow, Preiskurantgiz, 1967.
-
V. A. Grubman et al. Series of main thyristor electric drives for heavy carousel and lathe machines. In: Automated Electric Drive in the National Economy, vol. 2, “Energiya,” 1971.