Distribution Characteristic and Combined Optimization of Maximum Cogging Torque of Surface-Mounted Permanent-Magnet Machines

This paper examines the maximum cogging torque (MCT) distribution characteristic of surface-mounted permanent-magnet (SMPM) machines. The MCT distributions of SMPM machines with different pole-arc coefficients and different ratios of slot opening to slot pitch are studied using: 1) the Fourier series analysis together with the Maxwell stress tensor and 2) the finite-element method. Right triangle distribution regions of the optimal MCT are determined by comparing the MCT distribution contour maps obtained by the afore-mentioned two methods. Finally, a combined MCT optimization method for an SMPM with substantial savings in the optimization time, when compared with conventional methods, is proposed.