Investigation of Enhancing Reluctance Torque of a Delta-Type Variable Flux Memory Motor Having Large Flux Barrier for EV/HEV Traction

Delta-type permanent magnet (PM) arrangement and extended flux barriers are very effective in improving magnetization characteristics of variable flux memory motors (VFMMs). However, the reluctance torque tends to be declined because of small q-axis inductance. Therefore, a conventional VFMM using above two methods needs larger load current for achieving required maximum torque than that of a target traction motor which is mounted in TOYOTA PRIUS 4th generation. Hence, this paper proposes rotor shape that can increase the reluctance torque in order to achieve required maximum torque by applying same load current as that of the target motor. Finally, the proposed VFMM whose reluctance torque is improved can generate the target maximum torque with smaller load current than that of the conventional VFMM. In addition, the proposed VFMM has smaller maximum magnetizing current compared to that of the conventional model, and the proposed VFMM also indicates higher efficiency than that of the target traction motor in high speed region.