AC motor inverter control - includes variable frequency reversible oscillator and thyristors firing control circuit

摘要

The control circuit of an a.c. motor ensures improved performance, in partic. at low speed. The reversible movement of the motor is obtd. with an inverter and a variable frequency oscillator fot its frequency setting. The oscillator includes an integrator which provides a ramp output voltage with rise rate dependent on the d.c. component of the input signal. The clocking pulses and the sense signals are derived with positive and negative comparators shunting the integrator output. A logic gate is fitted between the comparators and the integrator resetting switch while the sense flip-flop of the comparators feeds a forward and reverse signal. The flip-flop is connected to ring counter controlling the firing pulses of the thyristor and receives signals from the logic gate via a delay line.