Abstract
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.
Highlights
As the core index of the technology’s advantages over traditional wired charging technology, the power transmission efficiency (PTE) of wireless power transfer (WPT) system plays a decisive role in the large-scale application of the technology
In view of the increase of coil effective series resistance (ESR) caused by substrate, based on theoretical modeling, simulation calculation, and experimental measurement, a systematic study on the variation rule of coil ESR with a single-layer substrate and double-layer substrate is carried out in this paper
When the size of single-layer substrate is close to the diameter of the coil outer ring, coil ESR is proportional to the area of ferrite
Summary
The wireless power transfer (WPT) technology uses energy carriers (e.g., magnetic field, electric field, electromagnetic wave, etc.) in the physical space and realizes the transfer of electric energy from the power supply side to the load side based on a no-wire contacting mode [1,2]. WPT technology in 2007 [1], academia and industry have done a lot of research for solving the problem of WPT system transmission distance and PTE improvement [12,13,14,15,16], and proposed frequency tracking [13], impedance matching [14], changing the coil structure, and adding magnetic circuit optimization structure [15,16]. The theoretical analysis of the coil resistance of single-layer and double-layer substrate with finite thickness and infinite area is studied respectively, followed by a discussion on the shifts of calculation methods when the substrate thickness is close to the skin depth.
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