Axial Flux In-wheel-motors for Vehicle Electrification

In-wheel-motors have emerged as a transformative technology in vehicle electrification, offering superior efficiency, compactness, and design flexibility over traditional off-wheel-motors. This study focuses on the advanced axial flux permanent magnet synchronous motors used as in-wheel-motors, which are critical for electric vehicle applications due to their high power and torque densities and minimized axial length. Automotive manufacturers increasingly adopt axial flux motors for their in-wheel-motors due to numerous advantages. The most appropriate configuration of axial flux motors is the single-stator double-rotor which supports a higher number of Neodymium permanent magnets, resulting in significantly improved power and torque densities, reduced iron losses, and enhanced efficiency compared to radial flux machines. This paper examines the state-of-the-art axial flux in-wheel-motors specifically designed for electric vehicles, highlighting the design considerations and engineering methodologies that contribute to their superior performance. By analyzing key performance metrics, including power and torque densities, efficiency, magnetic circuit topology, stator/rotor topology, winding configuration, drivetrain integration, and target applications, this paper demonstrates the potential of axial flux IWMs to drive a substantial transition into electric vehicles with allocated wheel torque control.