Voltage harmonic variation in three phase induction motors with different coil pitches

A pulse-width modulation (PWM) inverter feeding four different chorded three-phase induction motors was tested for low-order odd harmonic voltage component and efficiency at different loads. Total harmonic distortion (THD) due to 3rd, 5th and 9th harmonics was less in a motor with 160° coil pitch. Particular harmonic order for each coil pitch was suppressed and the efficiency of a 120° coil pitch motor was increased by 7.5%.