Comparison of Lumped Primary Coil Systems With SAE J2954 Secondary Coils for Dynamic Wireless Charging

In the SAE J2954 standard for stationary wireless charging of electric vehicles, two different coil geometries are proposed: The circular (C) and the double-D (DD) coil system. In the future, electric vehicles are expected to be equipped with the vehicle assembly (VA) coil geometry as proposed in the standard. This can be used as a design criterion for an electrified road, where the installed primary coils have to be compatible to the vehicle coil. In this paper, the two SAE systems are compared to each other regarding the coupling factor stability with a compatible primary side for dynamic wireless charging, i. e., charging while in motion. Therefore, two coil designs have been built up in laboratory, each consisting of three identical primary air coil pads compatible with the corresponding SAE secondary side. The results indicate that the coupling factor for the double-D coil system shows lesser variation along the path than for the circular coil system, but the absolute coupling factor is greater for the circular coil system.