Surface spiral coil design methodologies for high efficiency, high power, low flux density, large air-gap wireless power transfer systems

It was demonstrated that a surface spiral winding coil has low skin- and proximity effect losses in MHz, high power wireless power transfer systems. However, it was not clearly explained why the surface spiral winding coil is appropriate to use in kW level, low flux density, and safe wireless power transfer systems. Furthermore, research has not focused on the losses of a dielectric substrate of a surface spiral winding coil, even though the dielectric loss can overwhelm the skin- and proximity effect losses at MHz frequencies. In the first part of this paper, the benefits of the surface spiral winding coils for large air-gap, kW level wireless power transfer systems are discussed. In the following section, various sources of the power dissipation in surface spiral coils are identified. The discussion focuses on the dielectric losses in the substrates of surface spiral winding coils. Low-loss substrate design guidelines are proposed using the investigation results. The proposed design guidelines are evaluated by means of FEA simulation.