Coil design Guidelines for High Efficiency of Wireless Power Transfer (WPT)

Efficient operation of a wireless power transfer (WPT) system is a major design challenge in many WPT applications. This paper presents a method for designing a high efficiency WPT system when restrictions are imposed on receiver coil (Rx) size. The optimum pitch of the transmitter (Tx) and Rx coils is evaluated by analyzing the coil quality factor and coupling coefficient. Empirical formulae are proposed to derive generalized design guidelines for a given Rx size. The proposed empirical approach can be directly used for the design of a WPT with miniaturized Rx coils without using time consuming optimization algorithms. The proposed empirical expressions are validated with experimental results.