Speed control for async. three phase motor - has two separate windings, one used for driving by three phase current

摘要

The system may be used in passenger lifts. The first winding is used as the driving winding using the three phase supply. The other winding is used for braking the motor using d.c. Driving and braking effects are controlled by current control in accordance with control conditions. The nominal value for control varies in time, to give a programmed acceleration and deceleration curve. The acceleration increase is determined by a differential counter voltage in the reference element. The nominal voltage so produced continuously rises after the differentiation end at an adjustable slope until the maximum is reached.