Investigation on Stator Shifting Technique for Permanent Magnet Vernier Machines With Two-Slot Pitch Winding

This article investigates the stator shifting technique (SST) for permanent magnet Vernier (PMV) machines equipped with two-slot pitch winding (TSPW). By employing SST, TSPWs can be generated from the combination of two sets of fractional-slot concentrated windings, with various shift angles. The effects of various shift angles on armature magnetomotive force harmonic contents are explored. It shows that proper shift angles can be selected to preserve the working component while eliminating loss-producing harmonics. Besides, the implementation of various shift angles leads to uneven stator teeth structure, which affects field modulation. Therefore, the output torque capability, phase inductance, power factor, core losses, and fault-tolerance are affected by different shift angles. This article aims to exploit the full potential of TSPW-PMV machines by SST, considering the synthetic effects on harmonic reduction and field modulation. Through the exemplification of 24- slot, 19-rotor pole pair, and 5-armature pole pair PMV machines, it indicates SST is a more general and flexible design method that can provide new design opportunities and improve various performance metrics by introducing shift angle as an additional design variable. Finally, a prototype of the double-layer TSPW-PMV machine with optimal shift angle is fabricated for concept validations.