Electromagnetic Field Safety Analysis of a 7.7 kW Wireless Power Transfer System for Electric Vehicles

The safety of the electromagnetic environment of wireless power transfer (WPT) systems is one of the prerequisites for the application of wireless charging technology for electric vehicles (EVs). The electromagnetic characteristics of a wireless charging EV with a new 7.7 kW WPT system were modeled and analyzed in this paper. Firstly, a complete model of the magnetic coupler was built as a source of electromagnetic radiation, and an external excitation source was added by coupling the resonant coils to the double inductor-capacitor-capacitor (LCC-LCC) topology circuit model. Secondly, the finite element analysis software COMSOL Multiphysics was used to solve for the magneto-quasi -static values to verify the electromagnetic safety of the wireless charging process. Then, two charging scenarios were investigated when the GA and VA aligned and misaligned, involving lateral offset and longitudinal offset cases. Finally, the simulation results were compared and analyzed, showing that the values of electromagnetic fields become higher as the offset distance increases. In worst-case scenarios, the highest magnetic flux density (1.1 mu T) is observed in the virtual plane of the test on the left side of the vehicle, which occupies only 17.6% of the limits specified in ICNIRP 1998 (6.25 mu T), indicating a good EMF safety performance of the wireless charging system.