Investigation of PM Loss in Spoke-Type Permanent Magnet Vernier Motors With Different Stator Topologies for In-Wheel Direct Drive

In this article, the permanent magnet (PM) loss in spoke-type permanent magnet vernier motors (ST-PMVM) with different stator topologies is investigated and compared for in-wheel direct drive. First, four ST-PMVM with split-pole and open-slot stators are designed for the in-wheel limited requirements. Besides, based on the PM loss model, the dominant influences of both slot and subharmonics on PM loss are highlighted. Then, the quantitative contributions of the air-gap magnetic field harmonics on torque and PM loss are investigated, which embodies the inherent characteristic of larger PM loss in PMVM. Furthermore, the stator tooth parameters, the slot opening width, and auxiliary slot depth on torque and PM loss are described, and then a parameter titled as the slot opening ratio is introduced to evaluate the relationship of various slot opening width combinations. It shows that there exists an irreconcilable contradiction between the torque and PM loss in PMVM, especially in split-pole types. Finally, a prototype was manufactured, and the theoretical results and finite-element analysis results match well with the experimental results.