Torque ripple reduction design approach of permanent magnet machines based on circumferential pole-pair shift

Abstract

To tackle the torque pulsation challenge in permanent magnet machines (PMMs), this article proposes two design methods that involve shifting the permanent magnet pole pairs. Method 1 circumferentially shifts half of the pole pairs by half of the most significant pulsation period, while Method 2 shifts multiple pole pairs, with the angle of pole-pair displacement gradually increasing and evenly distributed over one selected pulsation cycle. Through the finite-element method (FEM) of various case studies with diverse pole-slot combinations, it is demonstrated that both proposed methods effectively suppress torque ripple, reduce cogging torque, and optimize back electromotive force distortion.