Transmission ofWireless Power in two-coil and four-coil systems using coupled mode theory

Wireless Power Transfer (WPT) systems are considered as sophisticated alternatives for modern day wired power transmission. Resonance based wireless power delivery is an efficient technique to transfer power over a relatively long distance. This paper presents a summary of a two-coil wireless power transfer system with the design theory, detailed formulations and simulation results using the coupled mode theory (CMT). Further by using the same theory, it explains the four-coil wireless power transfer system and its comparison with the two-coil wireless transfer power system. A four-coil energy transfer system can be optimized to provide maximum efficiency at a given operating distance. Design steps to obtain an efficient power transfer system are presented and a design example is provided. Further, the concept of relay is described and how relay effect can allow more distant and flexible energy transmission is shown.