Optimal Flux Modulation Pole Number in Vernier Permanent Magnet Synchronous Machines

This paper aims to identify the optimal flux modulation pole (FMP) number N-f in Vernier permanent magnet synchronous machines (VPMSMs) with concentrated tooth-coil windings. By using the developed analytical model, the influence of N-f on the machine back-EMF is firstly revealed and investigated. It is found that for a fixed machine size, there always exists an optimal N-f to maximize the torque, and the optimal N-f increases with the increase of machine size. In addition, critical design parameters including PM thickness and width of FMPs are parametrically analyzed by both analytical and finite element (FE) analyses. Results show that the VPMSMs with optimal N-f have advantages of higher torque density together with reduced PM volume, particularly for large-sized machines. Finally, two VPMSM prototypes with different N-f are manufactured and tested to validate the analyses.