Design of Magnetic Shielding for Reduction of Magnetic Near Field from Wireless Power Transfer System for Electric Vehicle

The wireless power transfer (WPT) system for electric vehicle (EV) typically has a pair of two magnetically coupled coils with the relatively large air gap between them. The time-varying currents flowing through the coils produce the intense magnetic near field around the coils which is inevitable to transfer the high power wirelessly. In this paper, we investigate the design of the coils with magnetic shielding with the air gap of 200 mm via the finite element analysis tool to minimize the magnetic near field from the WPT system for EV. The simulation results show that the minimization of the magnetic near field from the coils can be achieved by making the average winding diameters and the diameter of the ferrite shields to be root 2 and 3 times larger than the air gap length, respectively. For the case examined here, the magnitude of the magnetic near field is reduced over 29.12 % with the negligible loss of the power transfer efficiency.