Design Optimization Study on HEFSM with Flat Aspect Ratio for Enhancing Power Density and Efficiency

This paper focuses on a hybrid excitation flux switching motor (HEFSM) as one of the variable flux motors for EV/HEV propulsion. HEFSMs have the advantage in that all the active components are concentrated in the stator, which provides ease of cooling, whereas causes the drawback of being likely to occur severe magnetic saturation on the stator side. Therefore, a low L/D ratio, i.e., a flat aspect ratio, was selected, which offers a wide two-dimensional cross-section and mitigation of the magnetic saturation. In this paper, optimization of permanent magnet arrangement and grades under a low L/D ratio is addressed to enhance efficiency and power density over the entire speed range while satisfying design constraints and required performance for EV/HEV propulsion applications. The experimental verification shows that the motor efficiency of the newly designed HEFSM significantly exceeded that of the previously designed one, which reaches over 92% at the frequent operating point.