Effect of Pulsewidth Modulation on Electromagnetic Noise of Interior Permanent Magnet Synchronous Motor Drives

This paper investigates acoustic noise when an electric motor is fed with three-phase pulsewidth-modulated (PWM) currents with varying modulation indices. The procedure involves using a data-driven process to create a design space for different geometries of an interior permanent magnet synchronous motor. The motor structures are then analyzed using a finite-element analysis package to extract knowledge related to the sound pressure levels from the PWM excitation. It is demonstrated that sampling the air-gap space at a single time instant, which is a routine procedure in acoustic noise calculations, can result in an inaccurate estimation of the sound pressure levels, especially when the noise source is PWM motivated. Multiple-time sampling over the electrical period is proposed as a better approach for analyzing the sound pressure levels, irrespective of the type of supply current quality.