A new permanent-magnet vernier machine using a single layer winding layout for electric vehicles

Abstract

Permanent magnet (PM) vernier machines have shown promise in electric vehicle applications as they offer high torque density and low speed/high torque operation by introducing flux-modulation poles that modulate the high-speed armature rotating field and the low-speed PM rotor field. The non-overlap single layer windings provide a cost-effective design variation that eases manufacturing, reduces torque ripples, enhances voltage quality, and provides fault tolerant capability due to the negligible coupling between phases. The performance of such machines depends mainly on the proper selection of the pole and slot numbers. The preferred slots per phase per pole (SPP) ratios eliminate the effect of low order harmonics in the stator MMF, and thereby the vibration and stray loss are reduced. This paper proposes a new three-phase winding configuration based on the 20 slots/18 poles five-phase PM vernier machine which exploits the advantages of multiphase machine, including higher torque density and lower torque ripples, while fed from an off-the-shelf three-phase power converter. 2D Finite element analysis is used to verify the proposed design.