Air-Cooled Multi-Phase Dual-Winding In-Wheel Motor Integrated with Ultra Small SiC Module

This paper presents an air-cooled in-wheel motor integrated with an SiC inverter having high torque density, high gear ratio, and fault tolerant characteristics. Air-cooling is achieved using an integrated SiC power module, which utilizes a volume of only 5 cc for one phase, thus reducing the inverter loss. Additionally, a 5-phase permanent magnet synchronous motor with a dual winding structure is used to achieve a low current peak for the SiC module, and the dual winding structure can achieve the winding changeover technique to improve motor efficiency in the high-speed region. The motor is driven up to 20,000 min-1, and the in-wheel motor's gear ratio of 18:1 can generate an output of 1.2 kNm. The maximum output is 40 kW short term with a continuous output of 20 kW achieved by natural air-cooling in the wheel. The proposed design can achieve fault tolerance, an important attribute for the electric vehicle system. This product had been supported by a Japanese government project for 5 years from 2014 to 2018.