Experimental Comparison of Conventional and Bus-Clamping PWM Methods Based on Electrical and Acoustic Noise Spectra of Induction Motor Drives

The acoustic noise emitted by an induction motor powered by a voltage source inverter (VSI) is an environmental issue. Harmonics present in the stator current are the main reason for the increased acoustic noise in motor drives. The pulse-width modulation (PWM) technique used to modulate the inverter is akey factor in determining the magnitude of current harmonics. Bus-clamping PWM (BCPWM) techniques have got much attention nowadays due to reduced switching loss, compared with conventional space vector PWM (CSVPWM). In this paper, two BCPWM techniques, namely 60° and 30° BCPWM methods are compared with CSVPWM on the basis of electrical spectra as well as acoustic noise spectra. Experiments are conducted on a pulse-width-modulated VSI-fed induction motor drives. Harmonic analysis is carried out on the measured line-to-line voltage, stator current, and acoustic noise corresponding to the three methods at different fundamental and carrier frequencies. Based on the magnitude and phase of current harmonics, the frequency and normalized magnitude of dominant magnetic force waves are predicted theoretically. Theoretical predictions and experimental results both show that the magnitudes of dominant acoustic noise components around the carrier frequency are reduced significantly with these BCPWM methods compared with CSVPWM. Furthermore, it is shown that 30° BCPWM is better than 60° BCPWM in terms of acoustic pleasantness.