Power Factor Analysis in Spoke-Type Permanent Magnet Vernier Motors With Different Slot–Pole Combinations for In-Wheel Direct Drive

This article investigates the power factor characteristic in spoke-type permanent magnet Vernier motors (ST-PMVMs) with different slot–pole combinations for in-wheel direct drive. First, the working principle and power factor expression have been presented, and the influencing factors of the power factor have been targeted. Second, the relationship of slot and pole numbers is illustrated, and the general slot–pole combinations of PMVM with less armature magnetomotive force (MMF) harmonics have been derived and concluded. Then, the armature MMF harmonics, armature reaction magnetic field, and armature reaction reactance components under different slot–pole combinations are illustrated and compared, where a parameter to evaluate the ratio of useless leakage harmonic reactance is introduced. Next, the performances, such as the back EMF, armature reaction magnetic field, $d$ - and $q$ -axis inductances, output torque capability, and power factor, are all analyzed. Finally, a prototype was manufactured, and the experimental results match well with the theoretical and FEA results.