Reactive Shield for Reducing the Magnetic Field of a Wireless Power Transfer System with Dipole Coil Structure

Abstract

This paper proposes a reactive shield structure to reduce the leakage magnetic field of a wireless power transfer (WPT) system with a dipole coil structure. The reactive shield resonates at a frequency lower than that of the WPT system and operates in an inductive region where the reactance is positive. Therefore, the magnetic field generated by the shield coil is 180° different in phase from that generated by the transmitting coil, resulting in an effective reduction in the leakage magnetic field. The methodology for designing the reactive shield for the dipole coil structure is mathematically analyzed, and the current and magnetic field phases are compared. Its effectiveness has been validated through simulations and experiments. Specifically, the proposed method is validated through a 50 W class WPT experiment, which showed that the proposed shielding structure achieves efficiency reductions ranging from 0.3% to 1.5% and has a leakage magnetic field reduction effect of up to 67% compared to the comparison groups.