A Method for Researching the Influence of Relay Coil Location on the Transmission Efficiency of Wireless Power Transfer System

The transfer distance of the wireless power transfer (WPT) system with relay coil is longer, so this technology have a better practical perspective. But the location of the relay coil has a great impact on the transmission efficiency of the WPT system, and it is not easy to analyze. In order to research the influence law of the relay coil location on the transmission efficiency and obtain the optimal location, the paper firstly proposes the concept of relay coil location factor. And based on the location factor, a novel method for studying the influence of the relay coil location on the transmission efficiency is proposed. First, the mathematical model between the transmission efficiency and the location factor is built. Next, considering the transfer distance, coil radius, coil turns and load re-sistance, a lot of simulations are carried out to analyze the influence of the location factor on the transmission efficiency, respectively. The influence law and the optimal location factor were obtained with different parame-ters. Finally, a WPT system with relay coil was built for experiments. And the experiment results verify that the theoretical analysis is correct and the proposed method can simplify the analysis progress of the influence of re-lay coil location on the transmission efficiency. Moreover, the proposed method and the research conclusions can provide guidance for designing the multiple coils structure WPT system.