Exact Calculation of Leakage Magnetic Field for Wireless Power Transfer in 85-kHz Band

Abstract

Wireless power transfer, a technology for transmitting electric power to various devices without physical connection, has bee n widely. Although the magnetic field resonance method of wireless power transfer exhibits high efficiency, the leakage magnetic field due to the current flowing in the coil poses an issue. To date, leakage magnetic field strength has been obtained via electromagnetic field analysis. However, electromagnetic field analysis requires a long time and a large memory capacity. In this study, a method to obtain the leakage magnetic field strength with high accuracy solely via numerical calculations is derived. The accuracy of the calculation near the coil were decreased via the conventional calculation methods. At a distance of 1 m from the coil, the proposed method improved from 8.56 % to 2.12 % in the x-direction and from 11.25 % to 1.41 % in the y-direction. The validity of each magnetic field strength calculation method was confirmed via experiments. Given that only the input voltage to the transfer coil and the design value of the coil are used in the calculation of the magnetic field strength, this method can be useful in the design of wireless power transfer systems.