Analysis of Electromagnetic Vibration in Permanent Magnet Motors Based on Random PWM Technology

High vibration noise limits the application of permanent magnet motors in electric locomotive traction. This paper focuses on the high-frequency electromagnetic vibration in traction permanent magnet motors introduced by inverters. It explores the impact of periodic and random switching frequency pulse-width modulation (PWM) schemes on the high-frequency electromagnetic vibration performance of permanent magnet motors. The studied works are as follows: (1) The sources of higher-order harmonic components in the stator current are analyzed, and the characteristics of electromagnetic forces generated by these higher-order harmonic currents are studied. (2) The principles for suppressing high-frequency electromagnetic vibrations through random PWM are introduced. (3) The impact of the random switching frequency on higher-order harmonic currents in permanent magnet motors is analyzed through simulations. (4) The comprehensive experimental validation and evaluation of the random PWM technique are conducted on a permanent magnet motor. The results show that the vibration near the carrier frequency can be effectively weakened, but the overall vibration level has not been effectively reduced.