Rectifier with two function generators for electric motor supply - enables modulating sinusoidal or square waves to be selected with carrier frequency reduced for operator training

摘要

The PWM control set (20) incorporates a carrier frequency generator (22) producing a triangular waveform with a choice of two frequencies for normal operation and instructional purposes. Modulation at lower frequency is achieved with a four-phase function generator comprising a voltage-to-frequency converter (34), counter (36), digital (pref. EPROM) memory (38) and D/A converter (40). Pulses are applied (42) via operational amplifiers (24) to gate turn-off thyristors or power transistors (54, 58) which supply the motor current. ADVANTAGE - Influences of carrier and modulation function generators can be demonstrated on oscillograms of pulses at reduced carrier frequency.