Experimental Characterization and Modeling of a YASA P400 Axial Flux PM Traction Machine for Electric Vehicles

This paper investigates a popular off-the shelf performance traction machine, the yokeless and segmented armature YASA axial flux permanent magnet machine. A series of manual measurements and automated dynamometer tests were performed at various conditions. From these tests parameters are determined including friction and windage torque, phase resistance, permanent magnet flux linkage, and inductance. The efficiency, phase current, phase voltage, and power factor of the machine was measured over a wide torque and speed range, and these measurements were used to validate an analytical model of the machine. The measured efficiency map of the machine was integrated with a model of the Chevrolet Bolt electric vehicle (EV). The modeled performance of the YASA machine and of the Chevrolet Bolt EV machine were then compared, showing that for the HWFET drive cycle the YASA machine had about double the loss of the Bolt EV machine, translating to around 7% less range. The higher loss of the YASA machine likely has several causes, including higher phase resistance, significant friction, windage, and no-load iron losses, and the fact that Bolt EV machine was heavily optimized for this application while the YASA was optimized to be a highly power dense more general purpose machine.