Improvement of Strength Properties With Distributed Mortise Structure for Field Unit Type Magnet-assisted Wound Field Motor

A novel rotor structure for magnet-assisted wound field motors was proposed in this paper. In the pervious research, to improve the torque density of the magnet-assisted wound field motor, a field-unit-type rotor was proposed. This study showed that reluctance torque can be utilized in wound-field motors, contributing to improved torque density. However, when the same structure is applied to hybrid and electric vehicles, the strength characteristics on a high rotational speed was an issue. Therefore, this study proposed a novel rotor structure using a split rotor core and a distributed mortise structure. This structure improved the strength characteristics while maintaining the advantages of the field unit structure proposed in the previous study. To validate its effectiveness, the magnetic and mechanical properties of the proposed motor were verified using numerical and experimental verification, and the obtained results were compared with those a of conventional motor. The results confirmed that the proposed structure was effective in improving the performance of magnet-assisted wound field motors. In addition, the proposed motor was compared with an existing IPM motor of hybrid vehicle, and showed comparable mechanical output and high-efficiency in the high speed range.