Achieving Low Magnetic Flux Density and Low Electric Field Intensity for a Loosely Coupled 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 the 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 and the number of turns increase. In this paper, a multi-kW loosely coupled 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 coil-to-coil efficiency, magnetic and electric field distributions of different winding configurations are compared. The effects of coil radius, number of turns, interturn distance, transfer distance, and operating frequency on transfer efficiency, and magnetic and electric field distributions are investigated. The proposed methodology is evaluated with a 3 kW, 30 cm distance wireless power transfer design example by finite element analysis (FEA) and experiment tests.