10 kW Small-Gap Wireless Power Transfer System with Asymmetric Pads for Electric Vehicles

In wireless power transfer systems for electric vehicles, the volume, cost, and complexity of the system increase due to the consideration of a large air gap and misalignment between the transmitter pad and the receiver pad. This paper proposes a small-gap wireless power transfer system with asymmetric pads to increase the misalignment tolerance and enhance the performance of the wireless power transfer system. The proposed system reduces the air gap to a practical limit using a simple z-axis actuator while the x-axis is aligned by a mechanical stopper. The remaining y-axis misalignment is resolved with the asymmetric structure of the proposed pad. The proposed asymmetric pad enables the wireless power transfer system to maintain consistent performance under considerable y-axis misalignment. The experimental verification of the proposed asymmetric pad is conducted with a 10 kW system prototype. The maximum efficiency of 95.1 % was achieved under a negligible y-axis misalignment, and a 94.0 % efficiency was obtained with the maximum y-axis misalignment of 100 mm.