Axial flux machines drives: a new viable solution for electric cars

For electric car propulsion systems, the wheel motor is an application that requires the electrical machine has shape flexibility, compactness, robustness, high efficiency, and high torque. Axial flux machines are an interesting solution, where the motor is directly coupled to, or inside, the drive wheels. In this paper, axial flux induction and synchronous machines as wheel motor applications are presented and some considerations for each motor type are drawn by the authors. The structure with two rotors seems to be a very promising solution for both induction and synchronous machines. In the induction motor case, the two rotors can rotate at different speeds, thus the motor can act as a mechanical differential. The axial flux permanent magnet motor with two rotors is very compact and can be integrated inside the wheel.