Radial Flux In-Wheel-Motors for Vehicle Electrification

In-wheel motors (IWMs) have emerged as a promising technology for vehicle electrification, offering enhanced efficiency, compactness, and design flexibility compared to traditional onboard motors. The independent and direct drive capability of IWMs allows for the advanced application and integration of a wide range of chassis active safety systems, including anti-lock braking systems (ABS), traction control systems (TCS), electronic stability control (ESC), and torque vectoring (TV). IWM manufacturers utilise toroidal motor stators for IWM electric vehicle applications where axial length minimisation is essential. An outer rotor topology with radial flux Neodymium permanent magnets allows for hosting a higher number of pole-pairs on the rotor circumference enables accommodation of a higher number of pole pairs on the rotor circumference, significantly enhancing the power and torque densities compared to traditional cylindrical motors. Inspired by early conceptual IWMs introduced by pioneering automotive and tyre manufacturers, major automotive companies today have developed unique IWM designs, each with distinguishing features. The Protean IWM stands out for its high torque density, high efficiency, fault tolerance, direct drive, and improved packaging, making it an optimal choice for a propeller. This paper explores the state-of-the-art radial flux IWMs tailored specifically for electric vehicle (EV) applications. The unique features of the Protean IWM are examined in more detail due to its potential as a propeller suitable for both retrofitting traditional vehicles with minimal tear-out and for new electrified vehicles. Finally, a comparison of the features of various IWMs is conducted, highlighting the unique strengths of each system.