Optimising Ferrite-less Pad Reflection Winding with a Multi-Objective Genetic Algorithm

Inductive power transfer is the leading technology for roadway electric vehicle wireless power transfer. A robust magnetic design is desired for magnetic couplers (pads) that are to be buried in a road surface. Ferrite-less designs including a reflection winding have been shown to be a possible way to increase the robustness of pads and reduce leakage magnetic field. This paper presents a methodology to optimise the reflection winding of a ferrite-less pad with a genetic algorithm and presents the results of an example optimisation with an axisymmetric approximation of the wireless power transfer standard SAE J2954 WPT3/Z3 secondary pad, with the results verified in the finite element analysis package FEMM, and in the laboratory. The results verify the reflection coil concept and indicate that improvements in leakage per power can be gained by allowing the reflection winding to be non-planar.