A Novel Asymmetric-PM Hybrid-Magnetic-Circuit Variable Flux Memory Machine for Traction Applications

Abstract

In this paper, a novel asymmetric-permanent- magnet hybrid-magnetic-circuit variable flux memory machine (AH-VFMM) is proposed. The low coercive force (LCF) permanent magnets (PMs) are located on one biased side of the hybrid magnetic circuit branch, forming an AH configuration. Compared to its conventional symmetric-PM hybrid-magnetic-circuit (SH) counterpart, the proposed design benefits from the reduced usage of high coercive force (HCF) rare-earth magnet, alleviating the magnetic saturation to improve the flux regulation (FR) range, while the excellent load demagnetization withstand (LDW) capability can be still maintained. The topology evolution and operating principle of the proposed machine are introduced and described, respectively. Then, based on the combination of the magnetic equivalent circuit (MEC) method and Schwarz-Christoffel (SC) transformation, a hybrid analytical model is established to quantitatively reveal the mechanism of FR range extension, and facilitate the initial design of the machine. The electromagnetic characteristics of the proposed machine under different magnetization states (MSs) are investigated and compared with those of the conventional SH counterpart. Finally, an AH-VFMM prototype is manufactured, and the experimental measurements are carried out to verify the validity of the proposed design.