Active coil system for magnetic field reduction in an automotive wireless power transfer system

A novel design of active coils is proposed to reduce the magnetic field generated by the currents flowing into the coils of a wireless power transfer (WPT) system for recharging the batteries of an electric vehicle (EV). The main idea is to split the traditional active loop, in two separate shielding coils. They have semi-annular shape and are placed on the ground pad around the WPT primary coil. The geometry and excitation of the active coils are varied to minimize the magnetic field beside the active coils without degrading the WPT electrical performance.