A Novel Pole-Changing Permanent Magnet Vernier Motor

This article proposes a novel pole-changing (PC) permanent magnet (PM) Vernier machine (PC-PMVM), in which an unevenly distributed modulation tooth structure is adopted in the stator, and a set of three-phase PC-winding is installed in the stator slots. On the rotor, surface-mounted PMs are adopted to generate PM excitation field. First, the topology design principle of PC-PMVM is discussed for the purpose of PC, based on which a 12/34-pole PC-PMVM is proposed. The analytical analysis shows that there are a series of working harmonics in the air-gap and can be grouped into two different types with different phasor diagrams for realizing PC operation. Thus, the speed range can be widened greatly because of the different PM flux linkage and inductances before and after PC. Next, the electromagnetic performance of PC-PMVM is investigated by finite element analysis and compared with an interior PM motor and a PC induction motor. Finally, a prototype is manufactured and tested. The results verify the correctness of theoretical analysis, and show that the proposed motor owns both high torque density and excellent speed-widening capability benefiting from the PC design and PC operation.