Investigation of Permanent Magnet Vernier Machines From Armature Field Perspective
Yu Zhao, Dawei Li, Xiang Ren, Ronghai Qu
Abstract
Permanent magnet Vernier machines (PMVMs) have drawn more and more attention due to their high torque density, whereas the power factor of PMVMs is lower than that of regular permanent magnet synchronous machines (PMSMs). At present, the analysis of PMVMs is mainly from the perspective of PM rotors, and the research results suggest that there seems a relationship between torque density and power factor. However, from the PM rotor perspective, the relationship cannot be explained in principle. In this article, the performance of PMVMs is investigated from the viewpoint of armature fields, where both the high torque density and the low power factor have been clarified. It is indicated that the high torque density of PMVMs is attributed to high amplitudes and large variation gradient of armature working harmonic, which has the same pole-pair of PMs, whereas the power factor suffers from the lower proportion of armature working harmonic to total harmonics. Meanwhile, the negative coupling between torque capability and power factor is first revealed from the armature field perspective. Finally, two prototypes of 18/14/4 and 15/14/1 with the same 14-pole-pair PM rotors and different armature fields are built and tested, and the analysis results match well with finite element analysis (FEA) and experimental results.