Novel Permanent Magnet Shape for Cogging Torque and Torque Ripple Minimization in Surface-Mounted PM Motors

Abstract

This paper presents a novel sinusoidal permanent magnet (PM) shape for Surface-Mounted PM (SPM) Motors to minimize cogging torque and torque ripple. Previous work has shown sinusoidal PM structure can produce sinusoidal back EMF for reducing torque pulsation. In this paper, the sinusoidal PM pole shape is designed symmetrically in the axial direction, providing balanced motor structure, which turns out to achieve much less cogging torque and torque ripple. Motor characteristics such as back EMF, cogging torque and electromagnetic torque are analyzed by 3-D finite element method (FEM). In order to highlight the advantage of proposed PM shape, all simulation results are compared to conventional square PM shape and previous sinusoidal PM shape SPM motors.