Influence of step-skew on high-power outer-rotor permanent magnet motors for mining applications

Abstract

To address the issues of high torque ripple and unstable operation in high-power mining outer-rotor permanent magnet motors (ORPMMs), this study investigates a rotor step-skew technique aimed at enhancing operational smoothness. First, an analytical model of cogging torque that incorporates rotor skew is established based on the energy method, which clarifies the mechanism through which the skew angle influences torque attenuation. From this model, a method for determining the optimal skew angle to minimize cogging torque is derived. Second, a finite element analysis (FEA) model of the ORPMM is con-structed to compare electromagnetic characteristics such as no-load back electromotive force (EMF), cogging torque, and torque ripple under both non-skewed and variably skewed rotor conditions. The cogging torque calculated analytically is compared with FEA results, thereby validating the accuracy of the optimal skew angle determination method. Finally, prototype experiments are conducted to verify the accuracy of both the simulation and analytical models. This work provides theoretical foundations and technical support for torque ripple suppression and performance optimization in high-power mining outer-rotor motors.