Reduction of magnetic fields to human exposure from a wireless EV charger by a new cancelling method

The latest Electric Vehicles (EV)-related power electronics have attracted special interest as one of effective solutions to energy and environmental issues. In order to implement a promising EV battery charging equipment and its EMS infrastructures for carports in private houses and public buildings, Wireless Power Transfer (WPT)-based on-board chargers (OBC) are more suitable and acceptable from a practical point of view. The authors have developed cost-effective WPT-OBC embedding the voltage-fed quasi-resonant ZVS high-frequency inverter with a single IGBT switch, which operates under the condition of PWM-dependent PFM control scheme. In actual, leakage magnetic field exposure emitted from WPT assembly should follow the feasible guideline of ICNIRP. This paper presents a new conceptual magnetic shielding method which is able to reduce the leakage magnetic field exposure from the wireless Inductive Power Transfer (IPT) assembly. It is noted that this method is based on the combined magnetic shielding implementation which makes use of both magnetic flux path concept by magnetic material and magnetic field cancellation principle eddy current induced into the conductive plates. Furthermore, the effectiveness of the leakage magnetic shielding technique in WPT is proven by the analytical considerations and experimentally-observed data.