Achieving low magnetic flux density and low electric field intensity for an inductive wireless power transfer system

In most loosely coupled inductive wireless power transfer systems, the air-gap magnetic flux density between coils is still far above safety limit, which is a potential threat to human beings and animals. In addition, less attention is paid to the air-gap electric field intensity, which increases significantly as the operating frequency increases. In this paper, a multi-kW inductive wireless power transfer system general design methodology that can inherently achieve low air-gap center plane magnetic flux density and electric field intensity is proposed. The effects of coil radius, number of turns, inter-turn distance and operating frequency are investigated. Proposed methodology is evaluated with a 3 kW, 30 cm distance wireless power transfer design example by FEA and experiment tests. Power scaling law within air-gap center plane magnetic field and electric field safety limits is developed.