Feasibility Study of High Torque Density Yokeless and Segmented Armature Axial Flux Machine for High-Speed EV Drives

This paper presents a preliminary design and analysis of yokeless and segmented armature axial flux machines, intended to replace traditional radial flux machines in axle traction drive for battery electric vehicle applications. The focus is on torque density and the applicability of the machines in high-speed operations from an electromagnetic perspective. The approach taken in this paper is to benchmark a reference e-axle system without redesigning any other components, except for the machine itself. This allows for several design constraints to be directly adopted. To further narrow the design scope, different slot-pole combinations are compared based on their torque capability, material usage, torque density, and losses of each component, including magnet, copper, and iron losses at maximum speed. In addition, magnet segmentation is studied as a means to reduce magnet losses.