A Study of Downsizing the Motor for Traction Drive of a Hybrid Electric Vehicle by Use of High Coercivity Magnets

The distributed winding interior permanent magnet (IPM) motor is generally used for the traction drive of hybrid electric vehicle because it assumes wide torque-speed range. However, they have a big winding-overhang producing unnecessary copper-losses and extending the stator axial length. That reduces the torque density and increases the costs. The solution is using of concentrated windings. This solution makes it can significantly reduce (roughly 50 %) the winding-overhang. The increase of torque density is limited by permanent magnet demagnetization at high-current operation. To solve the problem, the high coercivity magnet is necessary, preventing the motor from demagnetizing. This paper examines the feasibility study of increasing torque density to the concentrated winding IPM motor with using of high coercivity magnet(2387 kA/m, 30 kOe). The results I got is the torque density can be increased 25 % compared to the conventional distributed winding motor, which realizes 25% downsizing of the motor.