Design of a High-Power Density Multi-MHz Capacitive Wireless Power Transfer System for Mobile Robots

Abstract

This paper introduces a methodology to design high-power density multi-MHz capacitive wireless power transfer (WPT) system for wirelessly charging mobile robots while focusing the fringing electric fields to be within safety limits. An optimal way to design efficient matching networks for the capacitive WPT system is proposed with a constraint on voltage developed across the coupling plates during the desired power transfer to limit electric fields. Furthermore, a methodology to determine charging pad dimensions for the capacitive WPT system is presented while meeting the desired target specifications for system efficiency, output power and power transfer density. A 6.78-MHz 3-cm air-gap 1.9-kW capacitive WPT system is designed, built and tested to validate the proposed design methodology. The prototype achieves a record power transfer density for a capacitive WPT system i.e., 95 kW/m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> transferring 1.9-kW with 90% peak efficiency.