Design and Analysis of an Improved-Power-Factor Trapezoid-Shape Permanent Magnet Vernier Machine With Hybrid Winding Connection

Permanent magnet vernier machines (PMVMs) can achieve high torque at low speeds due to the flux modulation effect, but their low power factor limits the applications in in-wheel motors and ship propulsion systems. This paper proposes a five-phase PMVM with a hybrid star-pentagon winding and a yokeless spoke-type rotor employing trapezoidal-shaped magnets, significantly improving both power factor and torque density. The hybrid winding configuration enhances the power factor by combining the benefits of star and pentagon windings, increasing the working harmonic contribution while maintaining excellent harmonic suppression. Furthermore, the yokeless spoke rotor utilizes oppositely magnetized trapezoidal magnets with a large cross-section to strengthen the flux focusing effect, thereby boosting magnet flux linkage and torque output. Finite element analysis (FEA) was conducted under identical overall dimensional constraints to compare the proposed machine with two existing five-phase machines that have been optimally designed. The proposed machine exhibits a higher proportion of effective armature flux and enhanced magnetic flux linkage. As a result, it delivers at least 19.6% higher torque than the other comparative models, albeit with a slight reduction in power factor. Finally, a prototype is fabricated and experimentally tested, validating that the proposed machine exhibits an output torque of 24.9 Nm and up to a power factor of 0.883.