Influence of Pole Ratio and Winding Pole Numbers on Performance and Optimal Design Parameters of Surface Permanent-Magnet Vernier Machines

In recent years, surface permanent-magnet vernier machines (SPMVM) have been attracting more and more attention for several advantages, including a high torque density and a simple mechanical structure. However, the influence of the pole ratio, which is defined as the ratio of rotor pole pair numbers to winding pole pair numbers, and the winding pole pair numbers on the performance of SPMVMs has not been investigated in literature. This paper mainly focuses on the effects of the pole ratio and the winding pole pair numbers on the torque capacity, power factor, torque ripple, and cogging torque of an SPMVM. The variations of optimal design parameters for maximum torque, such as the split ratio (the ratio of the stator inner diameter to the outer diameter), the slot opening width, and the permanent-magnet thickness, with the pole ratio and the winding pole pair numbers are also investigated by finite-element analysis. The analysis results reveal that the pole ratio and the winding pole pair numbers significantly influence the performance and optimal design parameters of the SPMVM. Finally, an SPMVM prototype is built, and experiments are conducted to validate the aforementioned results.