Performance of Large Low-Pole-Ratio Non-Overlap-Winding PM Vernier Motor

Permanent Magnet Vernier Motor (PMVM) is a new generation of permanent magnet (PM) motor that has attracted attention for direct drive applications, thanks to its ability to generate high torque, achieved through flux modulation effects. Many comparisons have been made between permanent magnet synchronous motors (PMSMs) and PMVMs in terms of performance and cost. However, these comparisons are not strictly fair in terms of cost, as the different power factors (PFs) of the two motors can significantly affect the cost of the drive system. This paper presents a comparative study of an optimized PMSM and an optimized low-gear-ratio PMVM for a 5-MW ship propulsion application. Both motors have the same PF and PM content, and share the same winding configuration, but differ in the number of PM poles on the rotor. The study evaluates both motors based on PF, torque characteristics, copper and core losses, efficiency, active mass and cost. The findings highlight that the low-gear-ratio PMVM outperforms the optimized PMSM in several aspects. It is lighter in weight and proves to be a superior candidate for this application due to its higher torque density, efficiency, and lower ripple torque.