A New Hybrid Concentrated-Winding Concept With Improved Power Factor for Permanent Magnet Vernier Machine

This article investigates a high power-factor permanent magnet vernier machine (PMVM) equipped with low-coupling hybrid concentrated-winding (CW). The proposed hybrid-CW, carrying both star- and delta-winding sets, exhibits a good filtering property to both sub- and super-order harmonics. Through the meticulous design of the short coil pitch, the ratio of inductance to magnet flux linkage is decreased, leading to a great improvement in power factor. The proposed low-coupling winding design contributes to further power factor improvement by reducing the inductance while retaining the magnet flux linkage. It is revealed that the mutual coupling between different coils of a single phase and that between different windings of three phases is suppressed significantly in the hybrid-CW, thus leading to a high power factor and potentially high fault tolerance. Finite element results show that the proposed hybrid-CW PMVM exhibits a significantly improved power factor up to 0.96 from 0.83 and 0.75, as compared with two counterpart PMVMs with open-slot and split-tooth structures, respectively. Benefiting from the magnetic gearing effect, the proposed PMVM has a promising active torque density of 40 N⋅m/L. Taking the end-winding volume into consideration, the proposed PMVM exhibits an actual torque density of 21.98 N⋅m/L, which is 22.52% and 52.43% higher than the investigated open-slot and split-tooth counterpart PMVMs. Finally, a prototype is fabricated and tested to validate the high-power-factor and high-torque-density features of the proposed hybrid-CW PMVM.