Surface Spiral Parallel and Antiparallel Winding Designs for High Efficiency, Low Spatial Voltage Stress, and Inductive Wireless Power Transfer Systems

Surface spiral winding (SSW) has been demonstrated to achieve low skin and proximity effects copper losses, and low air-gap magnetic flux density in MHz, kW level inductive wireless power transfer systems. The dielectric losses are still the limiting factor to further improve the coil-to-coil efficiency. In addition, high spatial voltage stress between the first turn and the end turn limits the maximum transferable power due to the voltage breakdown. This paper develops alternative coil configurations to reduce the copper loss, the dielectric losses, and the spatial voltage stress. Through emulating SSW using copper tubing, the dielectric losses and the spatial electric field between adjacent turns are reduced simultaneously. Two surface spiral parallel winding designs are proposed to reduce the equivalent series resistance and improve the coil-to-coil transfer efficiency. A surface spiral antiparallel winding design is proposed to equalize dynamic voltage stress between adjacent turns and improve power scalability while maintaining high coil-to-coil transfer efficiency.