EMF Reduction with Compensated Current RMS Based on Short Canceling Coils for Wireless Power Transfer Systems

Abstract

This study proposes and analyzes low-radiation-noise wireless power transfer (WPT) systems with active shielding. Current flows on the additional windings (canceling windings) around the WPT coils with power supplies are used to cancel the magnetic field generated by the WPT coils. The RMS values of the current flowing in the canceling windings are compensated by the active shielding from the utilization of the short-circuited canceling windings to achieve a zero magnetic field. As a result, a 1-kW transmission power and radiation noise reduction of 39.5dB is achieved with the proposed active shielding. The error between the estimated and measured current RMS is 6.2% at the lowest magnetic field. In addition, it is found that the transmission power with the proposed WPT system cancellation method is increased by the magnetic field reduction.