NVH Analysis of Rotor Step Skewing on Permanent Magnet Synchronous Motor

Rotor step skewing is one of the widespread techniques to mitigate cogging torque and reduce torque ripple on permanent magnet synchronous motor (PMSM). This technique also changes the distribution of the electromagnetic forces on the stator, which will impact the noise emitted from the motor. The prementioned effect haven't been studied a lot in the literature with the majority focusing only on the torque ripple effect. This paper introduces the application of a multi-physics workflow to analyze the impact of different types of rotor step skewing on a selected PMSM motor for EVs application and compare the results with baseline motor. At first, electromagnetic finite element (FE) model will be used to extract and analyze the excitation on the stator teeth. Then, the computed forces will be applied to mechanical FE model to predict the radiated noise from the motor housing at different speed. The paper also proposes a novel method to use a two-dimensional FE model to compute the electromagnetic forces, instead of otherwise necessary 3D dimensional analysis.