Basic Study on Efficiency Improvement of Hybrid Excitation Flux Switching Motor using Variably Magnetizable Permanent Magnets for Automotive Traction Drives

This paper deals with a hybrid excitation flux switching motor (HEFSM) employing a variably magnetizable permanent magnet as an automobile traction motor for a hybrid electric vehicle. Compared with the conventional HEFSM, a difference can be found on the stator body that newly utilizes the variably magnetizable permanent magnets adding to the conventional parts such as laminated steel core, three-phase armature coils, field excitation coils and constantly magnetized permanent magnets. A basic concept to improve motor efficiency is based on replacing the mmf of field excitation coils with that of the variably magnetizable permanent magnets. The magnetizing state of the variably magnetizable permanent magnet is adjusted properly according to operating conditions, resulting in the copper loss and iron loss reductions. FEA-based design and simulation as well as experimental test-based performance evaluation results of the proposed HEFSM show that the motor efficiencies under frequent operating conditions compete with those of the IPMSM installed on TOYOTA fourth-generation PRIUS.