Development of Dynamic Wireless Power Transfer Coils for 3rd Generation Wireless In-Wheel Motor

Short cruise range is a major issues in electric vehicles, and dynamic wireless power transfer has been proposed to solve this problem. In this study, a new dynamic power transfer system is introduced, called the hird generation wireless in-wheel motor, that integrates the drive circuit and motor. Additionally, a methodology of the transmitter and receiver coil design that can calculate inductance and resistance of the rectangular spiral coils in a fast manner is proposed. It considers the theoretical efficiency of coils, current of coils, and voltage of resonance capacitor as constraints. Inductance calculation models only use coordinates of coil edge and the distance between coil and ferrite core. The coils designed by the proposed method were manufactured and evaluated using an LCR meter. The calculation error of the self-inductance and mutual inductance was found to be ±9%. With the transmitter coil and receiver coil, an output and DC to DC efficiency of is 18kW and 95.2%, respectively, were obtained by actual wireless power transfer test.