Finite-element-simulation-assisted optimized design of an asymmetrical high-power inductive coupler with a large air gap for EV charging

Wireless Power Transfer (WPT) has become very popular due to improved safety and convenience provided by the cordless environment. Compared to wireless charging of small electronics, wireless charging of EVs has less variability in distance between transmitter coil (Tx) to receiver coil (Rx). Also, it is highly desirable to minimize the weight and size of Rx mounted on a car, while a larger Tx is employed on the charging platform to provide stronger and/or more uniform magnetic field. Most of the WPT papers for EVs in the literature [1]-[3] describe the realization of inductive couplers using air coils, while some authors use a high-permeability magnetic core [4], [5]. However, a well-defined approach on how to design the coupler is missing. This paper describes how a 3D FES program is used to optimize the coupler. It shows that for a typical design it is preferable to use a ferrite core and suggests how to optimize the core geometry as a function of the air gap.