Effect of Airgap Length on Electromagnetic Performance of Surface Mounted Permanent Magnet Vemier Machine

This paper investigates the effect of airgap length on the electromagnetic performance of 3kW surface mounted permanent magnet Vernier (SPM-V) machine. The performance is compared with a conventional surface mounted permanent magnet (SPM) machine with same airgap length using 2D Finite Element Analysis (2D FEA). For each airgap length, the slot/pole number combination for the SPM-V machine is investigated to achieve the optimal performance compared to the conventional SPM machine. The results show that the SPMV machine can achieve much higher torque capability than the conventional SPM machine at smaller airgap length. However, there is an optimal airgap length beyond which the torque performance of SPM-V machines drops below the conventional SPM counterparts. Moreover, unlike the conventional SPM machines, the power factor of SPM-V machines drops significantly with increase in airgap length.