Comparison Between a Series-Hybrid Variable-Flux Memory Motor and a Rare-Earth IPMSM

This paper compares a series-hybrid variable-flux memory motor with an equivalent optimized conventional rare-earth IPMSM for electric vehicle applications. Hybrid variable-flux motor technology with different magnetic circuit arrangements, such as series, parallel, and series-parallel, have been recently investigated for traction applications. The series-hybrid variable-flux motors (SHVFMs) have shown superiority for high torque and load demagnetization withstand capabilities. Yet, the literature lacks a detailed comparison between this evolving technology and the conventional IPMSMs for traction applications. Thus, this paper compares the two comprehensively, based on Finite Element (FE) Analysis supported by experimental results. The segregated power loss, efficiency, and power factor comparison is carried out for heavy and continuous load operation in the constant torque and field-weakening regions. It was found that for heavy load operations, the conventional IPMSM outperforms the SHVFM; however, the opposite is true for continuous load operations, significantly beyond the base speed. The magnet size/cost and inverter size are also discussed.