Circuits of non-reversing drives using TRPSh
Abstract Generated abstract
This paper examines non-reversing direct-current motor drives requiring wide-range speed regulation and rigid stabilization, proposing the use of a transformer regulated by shunt biasing with rectifier and motor as an alternative to magnetic amplifier, transformer, rectifier, and motor systems. It reports tests of several TRPSh based speed-control circuits for separately excited motors up to several kilowatts, comparing their dynamic stability and practical suitability under load, control, and supply-voltage disturbances. The authors identify preferred circuit arrangements and provide design recommendations for shunt dimensions, feedback, control and bias windings, and ballast resistance, indicating that such systems can achieve armature-voltage speed control over ranges of about 1:50 or more with speed-characteristic rigidity of roughly 1 to 2 percent.
Full Text
CIRCUITS OF NON-REVERSING DRIVES USING TRPSh
A. I. ZAITSEV, V. P. OBRUSNIK
(Presented by the scientific seminar of the Electromechanical Faculty)
In non-reversing drives requiring a wide range of regulation of the motor speed with rigid stabilization at a specified level, magnetic amplifier–rectifier–motor systems (MU–V–D) are widely used. However, in order to match the line voltage with the voltage supplied to the motor, in these systems it is often necessary to install a matching transformer. In such cases, instead of a transformer and a magnetic amplifier it is expedient to use a transformer regulated by shunt biasing (TRPSh). Possessing the same regulating capabilities as an MU paired with a transformer, but constituting a single structural unit, the TRPSh offers certain advantages, since it occupies less space in the installation, is more convenient to mount, and has better economic indicators. At the Department of Electrification of Industrial Enterprises of TPI, a number of speed-control circuits for a direct-current motor using the TRPSh–V–D system were tested. Below are presented circuits that can be recommended for regulating and stabilizing the speed of non-reversing drives with separately excited motors of up to several kilowatts.
In the circuits in Fig. 1a, b, c the following designations are used:
\(W_1, W_2\) — primary and secondary windings of the TRPSh,
\(W_{\mathrm{cm}}\) — bias winding,
\(W_{\mathrm{t}}\) — current-feedback winding,
\(W_{\mathrm{u}}\) — control winding,
\(R_{\mathrm{b}}\) — ballast nonlinear resistance, ensuring stable regulation of the TRPSh voltage in no-load operating modes.
TRPSh units must be made with external or internal feedback; in that case the systems presented here, without intermediate amplifiers, provide stable speed regulation by means of the armature voltage over a range of up to 1:50 and more, with rigidity of the speed characteristic of \((1 \div 2\%)\). From the standpoint of regulation, the circuit in Fig. 1a should be considered the best. The circuits in Fig. 1a, b are stable in dynamic modes. During tests, oscillations in
Fig. 1.
In the system, they were not caused even by abrupt changes in the load, the control current, or the voltage of the supply network. The circuit in Fig. 1v has one rectifier bridge fewer, but in practice it does not operate without additional correcting circuits, although when operating into a purely active load it should be considered preferable. With a motor load, however, the effect of the counter-e.m.f. on the shape and magnitude of the current in the current winding of the TRPSh has a significant effect on the stability of the control system.
In all circuits it is possible to provide current cutoff and dynamic braking, and to use intermediate amplifiers. If the TRPSh is made with shunts of ordinary transformer steel and silicon or germanium diodes are used in the rectifiers, then in order to ensure stiff speed characteristics and a wide range of motor-speed control it should have the following parameters:
- The shunt cross section relative to the cross section of the main magnetic core
\[ Q_{\text{sh}} = (0.8 \div 0.70) Q_{o}. \]
- The number of turns of the current winding with external feedback,
\[ W_{t} = 1.03 W_{2} \]
and with internal feedback
\[ W_{t} = 0.035 W_{2}. \]
It is desirable that, in the circuit in Fig. 1v, the resistance of the current winding not exceed the active resistance of the motor.
- The number of turns of the control winding
\[ W_{y} = \frac{I_{\text{dv.nom}} \cdot W_{2}}{I_{y\text{nom}}} \cdot (0.12 \div 0.15). \]
This winding must have a large voltage gain, at least \(10 \div 15\).
- The number of turns of the bias winding
\[ W_{\text{sm}} = \frac{I_{y\text{nom}} \cdot W_{y}}{I_{\text{sm.nom}}} (0.35 \div 0.5). \]
The ballast resistance \(R_{b}\) must provide a small current leakage within the range \((2 \div 3\%) I_{2\text{nom}}\). Current barretters were used in the investigations.
In principle, the TRPSh–V–D systems are analogous to MU–V–D systems and can be widely used alongside the latter.