Minimization of acoustic noise in variable speed induction motors using a modified PWM drive

This paper describes an effective way of reducing acoustic noise in a motor supplied from an adjustable speed PWM drive. The PWM patterns are selected to eliminate the most acoustically sensitive harmonics in the motor´s vibration spectra. This permits the PWM drive to use more economical yet slower switching devices while maintaining quiet operation. This method is applicable to both voltage source and current source inverters since the current waveform is used as the basis for eliminating the objectionable harmonics