Optimal Multi-Tooth Numbers for Vernier PM Synchronous Machines

This paper systematically investigates the effect of multi-tooth numbers on electromagnetic performances of conventional and consequent-pole (CP) vernier permanent magnet (PM) synchronous machines (VPMSMs), including average torque, overload capability, PM utilization, loss, efficiency, and power factor, etc. In particular, the influence of multi-tooth numbers on the unipolar end leakage flux of CP VPMSMs is investigated for the first time. It confirms that CP rotor and multi-tooth stator structures exhibit better field modulation effects compared with conventional north-south pole and non-multi-tooth stator structures. It reveals that there exists an optimal multi-tooth number for torque output capability and PM utilization, as well as unipolar end leakage flux. In particular, it shows that the multi-tooth stator structure helps save PM volume significantly for CP VPMSMs and suppress unipolar end leakage flux. The PM utilization rate of CP VPMSM with 5 multi-teeth is more than 50% higher than that with single-tooth structure while the unipolar end leakage flux is reduced by around 60%. However, the overload capability and power factor will be sacrificed. Finally, the prototypes with 2 and 3 multi-teeth numbers are manufactured and tested to verify the FEA analyses.