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

In this paper, to improve the power factor and torque of permanent magnet vernier (PMV) motor, a synergetic improvement method is newly presented, where the key is to investigate power factor and torque from the armature and PM field harmonics perspectives. First, the power factor is determined by the fundamental back electromotive force (EMF) and winding inductance. With the aid of magnetic field modulation, 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 power factor 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 power factor 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. Further, the power factor and torque are compared and evaluated. Finally, a prototype motor is built and tested for validation.