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 ar e selected to eliminate the most acoustically sensitive harmonics in t he motor's vibration spectra. This permits the PWM drive to use more e conomical yet slower switching devices while maintaining quiet operati on. This method is applicable to both voltage source and current sourc e inverters since the current waveform is used as the basis for elimin ating the objectionable harmonics.