Performance comparison of dual airgap and single airgap spoke-type Vernier permanent magnet machines

This paper presents a performance comparison of dual airgap and single airgap spoke-type Vernier permanent magnet machines (VPMMs). The dual airgap VPMM adopts the topologies with dual stator windings (DSW) and single stator windings (SSW). The key point is to demonstrate that the dual airgap VPMM with SSW could maintain better torque performance as compared to the VPMM with DSW, but greatly release the thermal and manufacture issues suffering from the inner stator winding. Further, the dual airgap VPMM with SSW is verified to work better in terms of torque performance than the Single airgap VPMM. The 2-D finite element method is used to compare the performance of the three models.

I. Introduction

The vernier permanent magnet machines (VPMMs) with the advantage of high torque density at low speed are suitable for direct drive applications. In particular, the dual excitation topology was introduced to further increase the torque density and efficiency [1]. However, the dual excitation VPMMs generally suffer the thermal and manufacture issues due to inner stator windings. In this paper, it provides an alternative design for the dual airgap VPMM, while the inner stator windings are removed. A performance comparison is carried out to demonstrate that the dual airgap VPMM with single stator windings could maintain better torque performance as compared to the VPMM with dual stator windings, but greatly release the thermal and manufacture issues, as well as working better with torque performance than the single airgap VPMM.