Analysis of Power Losses due to Magnetic Shielding for Electric Vehicle Wireless Charging

This paper proposes a design optimization method for a passive shielding in Wireless Power Transfer (WPT) systems. Starting from a charging device developed for electric vehicles, the main objective of this work is to study the effects of different shielding solutions on energy transmission efficiency and electromagnetic emissions. A Finite Element Method (FEM) is used to evaluate the ohmic losses related to different geometric configurations of both the plate shielding and the ferrite bars, as well as to the use of different materials for the shielding. As a result of the optimization procedure, the mutual inductance of the coils is restored to levels comparable to the non-shielded configuration. A separate set of FEM simulations reports reduced electromagnetic emissions for the optimized configuration, compliant with specific safety standard requirements. The final shielding configuration is composed by larger ferrite bars and by a shielding plate with a reduced radius. Finally, aluminium is used for the shield onboard of the electric vehicle, while the use of iron is proposed for the shield related to the ground section of the WPT system.