Design Considerations of Spoke-Array PM Vernier Machine for Different Power Levels

Spoke-Array permanent magnet vernier machine (SA-PMVM) is a competitive candidate for direct-drive applications owing to its high torque density, while neither the theoretical models nor relations between parameters and performances are well established due to the complex influence of flux barrier effects, which further lead to the lack of design guidance for SA-PMVMs. This paper is devoted to propose comprehensive design considerations of SA-PMVMs covering different power levels. Via constructing the closed-form per-unit formulations, the relations between machine parameters and electromagnetic performances, including torque density and power factor, are revealed. Further, the proper selections of critical design parameters, such as pole ratios, i.e., the pole-pair ratios of PM to armature winding, stator slot opening width to slot pitch ratios, and PM thickness to PM width ratios, are determined. Then, the general design method of SA-PMVM is proposed, and two finite element models are established to verify the theoretical analysis.