A Large Air-Gap Multi-MHz Capacitive Wireless Power Transfer System Using Compact Charging Pads

This paper presents a large air-gap multi-MHz capacitive WPT system utilizing innovatively designed compact charging pads. This charging pad comprises a pair of coupling plates that are used for power transfer, a metal sheet at its base that minimizes the impact of surrounding dissipative materials and a dielectric layer in-between. The effect of the dimensions of these structural components on the system's performance is studied and the tradeoffs between different choices are discussed. The design is supported by theoretical analysis and simulations, and is experimentally validated by a prototype 13.56-MHz 12-cm air-gap 500-W capacitive WPT system that utilizes these charging pads for power transfer. The prototype system achieves 88% efficiency while transferring 500 W power. The impact of foreign objects (including metal, wood, plastic, rubber, water, and snow) on the performance of this prototype system is also studied. The system's performance is found to be significantly impacted only for some of the objects in very close proximity to the coupling plates. Furthermore, to study the effectiveness of the charging pads in practical electric vehicle (EV) charging scenarios, the charging pad is embedded in materials used for roadway construction and the system performance is compared.