Reduction of vibration and acoustic noise in induction motor driven by three phase PWM AC chopper using static induction transistors

Three phase PWM chopper using SIT which chops three phase AC voltage with carrier frequency 20 KHz and controls induction motor, is proposed. Harmonic components in voltage and current waveforms do not appear within audio frequency band in this method. When each terminal of the motor are connected with capacitor 4 μF, the terminal voltage and line current waveforms of the motor driven by the chopper are almost sinusoidal waveforms. The motor is controlled in speed by changing ON time width τ of gate signal. Moreover power spectrum of the motor driven by the chopper is calculated and measured by using Fast Fourier Transform. Consequently reduction of vibration and acoustic noise in the motor driven by the chopper is confirmed at measurement.