On the use of eddy currents to facilitate wireless power transfer through metallic surfaces

This paper proposes that parasitic eddy currents can be utilized to facilitate and possibly enhance the power transfer capability of systems that utilize Near Field Magnetic Coupling (NFMC) for wireless charging. A proof of concept is provided where a receiver coil of diameter 27 mm harnesses more than 10W rectified power with greater than 60% AC-DC efficiency, while located within a dominantly metallic surface of dimensions 135 mm by 75 mm, and placed on a transmitter with a charge area 160 mm by 90 mm. A measurement and simulations based study has been performed to understand the phenomenon and explain the contribution of eddy currents towards wireless energy transfer. While the study was performed at 6.78 MHz, the findings are applicable at other frequencies.