Experimental Characterization and Modeling of a YASA P400 Axial Flux PM Traction Machine for Performance Analysis of a Chevy Bolt EV

This paper investigates off-the shelf performance traction machine, a yokeless and segmented armature (YASA) axial flux surface permanent magnet machine, model P400HC from YASA Motors. 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, speed, and dc bus voltage range up to around the maximum ratings given by the manufacturer. A range of d-q current values were tested, showing that the machine is slightly salient since maximum torque is achieved when including a small amount of d-axis current. A Chevrolet Bolt electric vehicle (EV) was modeled with the YASA Motors machine and the stock Bolt EV machine. Over four different vehicle drive cycles, the YASA Motors machine was shown to be considerably more lossy than the Bolt EV machine, thereby achieving 4% to 6% less range. The higher loss of the YASA Motors 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 an EV application while the YASA Motors machine was optimized to be a highly power dense more general-purpose machine.