Torque Improvement of Magnet-Assisted Wound Field Motor With Field Unit Type Rotor

This article presents a novel magnet-assisted wound field motor with a field-unit-type rotor. In conventional magnet-assisted wound field motors, the rotor core cannot be placed on the q-axis to pass through the winding nozzle. Therefore, conventional motors cannot utilize reluctance torque, and arrangement of magnets is limited. In the proposed motor, the main rotor core and pole piece, on which the field winding is wound, are separate, and the field coil, bobbin, and pole piece are integrated to form field units, which are inserted into the main rotor core in the axial direction. This structure allows the core to be placed on the q-axis of the main rotor core, thereby achieving higher torque density than conventional motors. In this study, to verify the effectiveness of the proposed motor, its torque characteristics are compared with those of the conventional motor using finite element method. The numerical results show that the proposed magnet-assisted wound field motor achieved higher torque than that of conventional motors. Moreover, to validate the analysis results, experimental tests are conducted using prototype motor. By comparing the experimental and simulation results, the high torque density effect, which revealed by the numerical analysis, can be confirmed to be reasonable. In this article, the magnet-assisted wound field motor proposed in the previous study is referred to as the conventional motor, and the magnet-assisted wound field motor using the field unit structure is referred to as the proposed motor.