A High Power Factor PM Vernier Machine with Segmented-Stator

Permanent magnet vernier machines (PMVMs) are attractive candidates for direct-drive applications due to their high torque density. However, they suffer from low power factor owing to the large harmonic leakage inductance caused by armature no-working harmonics. This paper proposes a high power factor PMVM with segmented-stator. Benefited from segmented-stator structure, the additional magneto-motive force (MMF) has been introduced, which not only can weaken the low order armature no-working harmonics and corresponding harmonic leakages, but also can strengthen armature working magnetic field by the cooperation of multiple working harmonics. As a result, both the high power factor and average torque can be achieved. Further, the performances of the proposed PMVM have been comprehensively analyzed and compared with regular PM synchronous machine (PMSM) and regular PMVM. It indicates that compared to the regular PMVM, the power factor of proposed PMVM at current density 5 A/mm2 can be improved from 0.85 to 0.96, and torque density can be enhanced from 15.4 Nm/L to 16.7 Nm/L, respectively. Finally, a prototype with 6-segmented-stator 13-pole-pair PM rotor is manufactured and tested, where experimental results match well with finite element analysis (FEA), which verifies the superiorities of the proposed PMVM.