Torque density maximization of vernier machine by using series compensation

Abstract

This paper deals with the design of SPM vernier machine with high slots/pole/phase q, to get higher torque density as well as improved power factor by applying the concept of series compensation. The torque density of a vernier machine can be enhanced by increasing the number of slots/pole/phase q, but as q increases the drastic increase in the reactance makes the power factor even worse. Therefore, it is general to choose low q, even if higher torque can be obtained with higher q. In this study, the idea of series compensation is applied to get vernier machine with high q without the low power factor problem. Series compensation is performed by supplying the desired reactive power to the machine from an additional inverter with a floating capacitor. To validate the theoretical analyses, three SPM vernier machines with different q (1 ∼ 3) are designed and then analyzed by using FEM.