Magnetic Field Distribution of Resonance Coupling Coils of 7.7 kW Wireless Charging System

This paper designs a 7.7 kW power resonance wireless charging system for electric vehicles. The resonant frequency of this system is 85 kHz, and the coupling coil adopts LCC compensation circuit. A wireless charging system circuit model was built and simulated by MATLAB/Simulink to obtain the currents on the primary and secondary coils. The 3D FEA software ANSYS Maxwell was used to model circular coils with ferrites to predict the magnetic field distribution in the vehicle environment. According to the SAE J2954, four points on the body and the surrounding area and four points on the driver’s seat were selected as markers, respectively. Studying three working conditions of the alignment and offset of the coupling coil, the magnetic field distribution of the entire coupled coil and each marker are observed. A pair of aluminum shielding shells was designed for the magnetic field distribution of the coupling coils. The magnetic field strength of the coils with or without shielded aluminum shells was simulated and compared. Then, the inhibitory effect of the shielding shell on the leakage magnetic field of the resonance coupling coils was verified. Safety of magnetic field distribution of a wireless charging system with a shielded aluminum shell was explained.