Design and Modeling of Ferrite Core Geometry for Inductive Wireless Chargers of Electric Vehicles

In order to maximize the inductive link efficiency in wireless electric vehicle chargers, a ferrite layer is added to improve the coupling performance and reduce the leakage of flux to the surrounding ferrous materials. The geometry of ferrite directly affects the self and mutual inductance of the primary and secondary coils and accordingly their coupling factor. Three ferrite geometries are investigated in this work and their coupling behavior is studied and compared to that of a ferrite sheet. Based on the simulation results, the geometry in which ferrite bars are aligned perpendicular to the current conduction path provides the highest coupling factor and highest inductive link efficiency at perfect alignment conditions over a range of air gaps from 10 cm to 30 cm, while having the smallest ferrite surface area. Hence, this geometry is recommended to be used for closely aligned rectangular EV coupling coils.