A Reluctance-based Model for the Design of Inductive Power Transfer Coils

Ferrite is generally added to the transmitting and receiving coils used for inductive power transfer (IPT) to improve magnetic performance. To reduce coil weight and cost, finite element method (FEM) modelling may be employed to minimize the amount of ferrite used and optimize its placement. However, this approach is time-consuming and provides very limited design insight. Therefore, this paper proposes an analytical approach, based on magnetic reluctance, to aid in the design of IPT coils. It is based on modelling the air gap between transmitting and receiving coils as a network of reluctances, and facilitates design insight through allowing key analytical relationships between magnetic field and coil design parameters to be developed. Results from the proposed analytical model are benchmarked against those from FEM for an IPT coil implemented with a circular winding and with commonly used ferrite strips. The results verify the accuracy of the proposed analytical model.