Cogging torque suppression for IPMSM based on flux harmonic configuration

Abstract

Cogging torque, an undesirable pulsating torque inherent in permanent magnet (PM) machines, is caused by the harmonic interaction between rotor flux and airgap reluctance. Therefore, reducing cogging torque can be achieved by minimizing the undesired harmonics of the rotor flux. However, completely eliminating flux harmonics to achieve a purely sinusoidal flux is challenging, especially for interior-PM machines. As an alternative approach, this article presents a new design method for suppressing cogging torque by configuring the specific odd-order harmonics of the rotor flux. Specifically, the desired flux harmonics is configured by artificially shaping the rotor profile to modulate even-order rotor reluctance harmonics. The proposed method requires minimal parametric design and has minimal impact on other critical performance aspects of the machine due to the limited changes made to its structure. This article provides a comprehensive implementation pathway for the proposed method, supported by detailed analysis through multiple case studies. Furthermore, the effectiveness of the proposed method is validated through extensive simulations and experiments, confirming its capability to suppress cogging torque and overall torque ripple.