Research on magnetic field distribution and characteristics of a 3.7 kW wireless charging system for electric vehicles under offset

A 3.7 kW resonant wireless charging system (WCS) is proposed to realize the energy transmission for electric vehicles. In addition to designing the electrical modules functionally, coupling coils are designed and verified by physical prototype, which guarantees the accuracy of coils and subsequent simulations. Then, we focus on the magnetic field distribution of coupling coils in the vehicle environment. Four points (A1, A2, A3, A4) in different regions and three points (the head B1, chest B2 and cushion B3) in the driving seat are helped to measure the magnetic field strength. The magnetic field distribution of coils under five offsets of 60 mm, 120 mm, 180 mm, 240 mm and 300 mm are analyzed theoretically and simulated correspondingly. The simulation results indicate that the magnetic field strength of test points are within the limits, but the strength at A3 is larger than 30.4 A/m required by SAE J2954 at 40% offset and 50% offset. Taking into account the composition of the actual magnetic field, the magnetic field distribution due to side-band and odd harmonic current are also obtained. An experimental bench for the proposed 3.7 kW WCS is built to validate the rightness and feasibility of the simulated scheme. The results of simulation and experiments of magnetic field distribution have less error and are often in good agreement.