Principle of work of the system CR-M (figure 2).

The armature of hoisting plant motor in the system of CR-M couples power supply from the non-reverse controlled thyristor rectifier of U1 through a power transformer T1. For smoothing the pulsations of the rectified current in circuit of motor armature M reactor L is included. The excitation winding of motor couples a power supply from the non-reverse controlled thyristor rectifier U2 with a transformer T2. Speed and current feedbacks are used in circuit for providing necessary variation law of skips movement speed in periods of acceleration and braking, stabilizing of speed in periods of uniform motion, protecting electric motor from overloads. Speed feedback signal in form of voltage UBR IS taken from accelerometer BR and given to speed controller AR circuit. The regulator speed has transfer function of P-controller (proportional controller). Current feedback signal in form of voltage Urs is taken from the current sensor UA and given to the current controller AA. Output voltage of current sensor UA is proportional to the armature current of motor M. Current controller has transfer function of PI-controller (proportional-plus-integral action controller).

A control of hoisting plant motor speed can be manual or automatic. At manual control a control signal is given by selsyn controller KA. At automatic control the step control signal is taken from the path-control transducer and acts on intensity setting devise AJ (has a transfer function of integrator) which is made to produce voltage ramp. This voltage is given to the speed controller AR.

Setting voltage Uset in input of speed controller AR is proportional with the set speed. It is compared to the signal (by voltage) of actual speed, measured by accelerometer BR. Control action of speed controller is formed by speed deviation value ??v and accepted law of control, realized by the controller AR. From the output of speed controller AR control signal is given to controller AA. On the input of current controller AA control signal from controller AR is compared with voltage proportional to the armature current (from BR). Control signal is formed on the output of AA in accordance to the law of control. It is given to the input of pulse-phase control system AU1 of rectifier U1 for the variation of rectified voltage and consequently motor speed of hoisting plant for cutting of speed deviation value δv.

For current limitation at the excessive loadings of motor the feedback circuit of speed controller AR is bypassed by two voltage-reference diodes VD1 and VD2, included back-to-back for limitation of AR output voltage. At the excessive loadings motor cutoff current is defined by breakdown voltage of voltage-reference diodes.

Application of controlled rectifier in the circuit of excitation winding LM of motor M allows to support current constancy in spite of it’s voltage supply and motor temperature alteration. An excitation current feedback is used for this purpose.