Ferromagnetic Design of Coils Considering Misalignment Effects for a SAE J2954-Compliant EV Wireless Charger

In electric vehicle (EV) wireless charging, the misalignment between coils is an unavoidable issue that has been widely addressed in literature. One of the consequences of misalignment between coils is the variation of the self-inductance value. Additionally, it should be mentioned that ferromagnetic material is used to improve the system overall performance. Thus, this article studies the possibility of using the self-inductance variations as a criterion to determine the optimal ferromagnetic material layout, so that the effects of misalignment can be alleviated. For this reason, five different ferromagnetic topologies have been proposed, to perform a comparative analysis between them. The amount, size and layout of ferromagnetic material have been theoretically analyzed under realistic conditions and then, simulated through advanced simulation tools. Once the relations between misalignment and self-inductances, as well as ferrite layouts and self-inductances values have been achieved, it is determined that there is an optimal topology that leads to lower variations of self-inductances and, thus, presents a better performance under misalignment situations. This study has been performed and experimentally validated for a prototype of a SAE J2954-compliant EV 3.7-kW wireless charger, with a good agreement between simulated and experimental values.