The supply and braking circuit, for a d.c. motor, has thyristors in the motor rectifier to short-circuit the back-e.m.f. and brake the motor when the supply fails. When the motor supply fails firing pulses are generated by a control circuit and applied to the thyristors. The rectifier unit contains an isolation transformer whose centre-tapped secondary winding is connected across the rectifier bridge input. The tapping point is earthed. The firing pulses for the thyristors are generated by an oscillator that supplies a pulse amplifier. The advantages of the circuit are its simplicity and cheapness.
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