Improvement of Power Factor and Torque of a PM Vernier Motor From Perspective of Armature and PM Field Harmonics

In this article, to improve the power factor (PF) and torque of permanent magnet Vernier (PMV) motor, a synergetic improvement method is newly presented, where the key is to investigate PF and torque from the armature and permanent magnet (PM) field harmonics perspectives. First, the PF is determined by the fundamental back electromotive force (EMF) and winding inductance. With the aid of magnetic field modulation (MFM), armature harmonics and inductance as well as PM harmonics and back EMF are rethought and modeled. Based on this, the leading armature and PM harmonics that affect the PF are recognized. Similarly, the airgap harmonics, which make the dominant contribution to the torque, are also determined. Then, by clarifying the critical role of these harmonics, the synergetic improvement mechanism of PF and torque is summarized. Meanwhile, for validating the proposed method, the leading harmonics are purposefully selected as the optimization objectives to achieve the high-performance design of the motor. Furthermore, the PF and torque are compared and evaluated. Finally, a prototype motor is built and tested for validation.