Optimum Design Study on HEFSM Using Variably Magnetizable PM with Low L/D Ratio and Novel PM Arrangement for EV/HEV Traction Applications

This paper focuses on a hybrid excitation flux switching motor (HEFSM) using variably magnetizable permanent magnets (VM-PMs) as variable flux motors for EV/HEV propulsion. The HEFSM makes an energization of field excitation coil unnecessary for most of the operating conditions so that it enlarges high efficiency operating area thanks to reductions of both copper and iron losses by adequately controlling magnetization state of the VM-PMs according to given operating conditions. In this paper, a new HEFSM design is proposed, which employs a novel PM arrangement as well as a flat motor shape with an optimum L/D ratio aiming at total PM usage reduction and the variable flux capability and maximum torque improvement. FEA-based simulation results show that the motor efficiency and variable flux capability of the proposed HEFSM are comparable with those of a previous PM-rich HEFSM while satisfying the target maximum torque and demagnetization tolerability of PMs under the total PM usage limitation.