Comparison of Large Air-Gap Inductive and Capacitive Wireless Power Transfer Systems

This paper presents a theoretical comparison of large air-gap inductive and capacitive wireless power transfer (WPT) systems. The maximum power transfer capabilities of these WPT systems are analytically formulated in terms of their geometrical and electrical parameters while adhering to their physical limits, such as core saturation and air breakdown. The maximum achievable efficiency in these systems are expressed in terms of their system specifications, and the tradeoffs between their efficiency and power transfer density are compared. The effect of operating frequency on the power transfer capability and efficiency is also analyzed. The analytical predictions are validated using two multi-MHz kW-level capacitive WPT prototypes.