A 3.75-kW High-Power-Transfer-Density Capacitive Wireless Charging System for EVs Utilizing Toro idal-Interleaved-Foil Coupled Inductors

This paper presents a multi-kilowatt-scale high-power-transfer-density high-efficiency capacitive wireless power transfer (WPT) system suitable for electric vehicle (EV) charging. The system's high performance is enabled by innovative toroidal-interleaved-foil (TIF) coupled-inductor based matching networks. These matching networks also leverage the charging environment's parasitic capacitances to provide gain and reactive compensation. This new coupled inductor design is optimized to minimize losses while achieving a sufficiently high self-resonance frequency. TIF coupled inductors optimized for a 3.75-kW capacitive WPT system achieve a quality factor of 2055 and self-resonance frequency of 22.3 MHz. A 13.56-MHz 12-cm air-gap 22-cm diameter coupling-plate prototype capacitive WPT system using TIF coupled inductors is designed, built and tested. This system achieves record-breaking performance for a capacitive EV charging system, transferring 3.75 kW at an efficiency of 94.7%, corresponding to a power transfer density of 49.4 kW/m².