Control system maintaining supply to electric motor in event of power perturbations - includes oscillator controlled by pulse width modulation, providing compensating supply if interruption is detected

摘要

The electric motor (32) is provided with an oscillator (37) in the event of a loss of supply voltage. The oscillator is controlled by modulation of the width of pulses. The supply voltage (Vd) is measured continuously on the input terminals (40) of the oscillator, and the signal obtained is filtered by a low pass filter (41). An average value of the voltage (Vdm) is calculated. In the event of a fall in this average value, this fall is compensated by keeping constant the expression (mi x Vdm/w), where mi is the pulse width modulation index, and w is the beat frequency of the stator of the motor. USE - Control of electronic frequency convertors supplying asynchronous electric motors.