A Multiphysics Approach to Mitigate Pulse-Width-Modulation-Induced Acoustic Noise in Permanent Magnet Synchronous Motor Drives for Electric Vehicles

This article investigates high-frequency noise in permanent magnet synchronous motors (PMSMs) for electric vehicles, originating from pulse width modulation (PWM). A theoretical model is developed to formulate the phase voltage under space vector PWM (SVPWM), explicitly accounting for the additional harmonic components generated by the discrete-time voltage update in digital control systems. This derived voltage waveform serves as the excitation source in an electromagnetic finite-element model, from which the PWM current harmonics and their resulting high-frequency electromagnetic forces are computed. Critical components of the electromagnetic force are then extracted through two-dimensional Fourier transform. A structural model of the motor, incorporating practical assembly constraints, is established and validated by experimental modal tests on a fully assembled motor unit. To enable rapid noise prediction over the wide speed range, vibro-acoustic transfer functions are introduced. The predicted noise shows good agreement with experimental data. Leveraging this multiphysics model, the influence of switching frequency on noise characteristics is analyzed. The study identifies that avoiding excitation of the motor’s zero-order mode is critical for noise suppression. Accordingly, an optimal frequency-hopping strategy is proposed. Experimental validation confirms the strategy’s effectiveness in reducing noise over the wide speed range.