Power Factor Analysis of Flux Modulated Dual-PM Excited Machines based on PM and Armature Flux Linkages

Abstract

Flux modulated dual-permanent magnet (PM) excited machine (FMDPMM) has become a promising candidate for direct-drive applications, featuring high torque density and efficiency. However, it usually suffers from a low power factor (PF) due to the imbalanced PM and armature flux linkages, which are mainly caused by the abundant PM and armature field harmonics. To address the problem, a comprehensive PF analysis of FMDPMM is conducted in this paper based on PM and armature flux linkages. First, the dominant PM and armature field harmonics contributing to the corresponding flux linkages are investigated using a simplified magneto motive force (MMF)-permeance model. Based on the qualitative analysis, several practical design guidelines are presented to improve the PF of FMDPMM. Then, the dominant field harmonics and flux linkage contributions of two FMDPMMs with different PM arrangements and winding configurations are comparatively analyzed, quantitatively verifying the effectiveness of the proposed guidelines for PF improvement. The results demonstrate that, by taking advantage of high PM flux linkage, low non-working armature flux linkage, and proper filtering effect of armature windings, MDPMM can simultaneously achieve a high PF and a large torque density. Finally, a prototype is manufactured for validation.