Design of a permanent-magnet direct-driven wheel motor drive for electric vehicle

This paper presents a high efficiency direct wheel motor drive for electric vehicles (EVs). The proposed motor is a permanent magnet square-wave motor whose rotor with rare earth magnets forms the outside of the motor to be set within each wheel tyre to realize the direct drive. In order to achieve the direct drive without any mechanical transmission for EVs, the wheel motor has been designed as a low-speed high-torque motor. The design and optimization of the motor was done with the aid of finite element electromagnetic field analysis. The advanced motor control strategy, which could ensure the wheel motor drive runs efficiently in the entire permitted speed and load range, is also discussed. The design procedure of the 6.2 kW, 1000 rpm wheel motor drive and its technical data are given in this paper