Magnetic field emissions for ferrite and non-ferrite geometries for wireless power transfer to vehicles

Minimizing magnetic field emissions to surroundings are one of the most challenging design criteria for wireless power transfer to vehicles. In this paper, concept of division of the emissions into three zones (primary, secondary, and combined zone) in the vertical direction is introduced. For geometries without ferrite, these zones can be defined only on basis of distance from coils. The simulation results indicate that magnetic field profile in the surroundings is influenced for ferrite based geometries and the three zones tend to overlap. This overlapping is studied via Comsol simulations for vertical separation between the coils in range of 100–180 mm. It is observed that lower vertical separation results in higher overlapping of the zones and the coils behave as they are effectively placed close to center of air gap. The analysis in this work provides a better understanding of the space profile of magnetic field emissions (with and without ferrite) for wireless power transfer to vehicles.