The Influence of Substrate Size Changes on the Coil Resistance of the Wireless Power Transfer System

Wireless power transfer (WPT) technology has been widely used in many fields. Nevertheless, in the field of high power transmission, such as the WPT system of electric vehicles, the power transmission efficiency of WPT system lags behind that of wired charging due to losses brought by substrate shielding materials. In this regard, the conduction resistance of Litz-wire coils without substrate is analyzed first in this paper. Secondly, the induction resistance of the coil with single-layer and double-layer substrate materials is modeled. Then, through the establishment of a coil simulation and experimental platform with a single-layer substrate, a contrastive analysis of the variation trend of coil equivalent series resistance (coil ESR) at changing thickness and area and constant volume of the substrate is carried out in combination with the theory. The variation law of coil ESR at changing thickness and area and constant volume of double-layer substrate is also explored at the end of this paper. This is expected to contribute to the reduction of coil losses in the WPT system through a systematic study of the influence of substrate size changes on the coil resistance of the WPT system.