CONTROLLER OR INDUCTION MOTOR

PURPOSE:To remove a beat phenomenon in the rotation of a motor by insulating voltage information of a high voltage DC circuit to a control circuit side by a photocoupler to control V/F, thereby removing the ripple of a power source. CONSTITUTION:Voltage information from a V/F converter 26 is input through an insulating pulse transmitter 27 having a photocoupler and a pulse transformer to an F/V converter 28. A PWM logic circuit 30 decides the output frequency according to a signal of an output frequency command 29 and a V/F from the DC voltage from the converter 28 to transmit a PWM signal to a base drive circuit 31. Thus, the variation in the input voltage of an inverter and the ripple of a DC circuit are removed to operate stably.