Study on maximum air-gap and efficiency of Magnetic Resonant Coupling for Wireless Power Transfer using Equivalent Circuit

The progress of technology in the field of Wireless Power Transfer in the last few years is remarkable. The difference between traditional technology and today´s technology is that a transforming power across large air pas can be achieved through recent research. Much electric equipment is proposed- both small one and large. For example, Wireless Power Transfer for small equipment (mobile phone and laptop) and for large equipment (electric vehicle). Furthermore, replacing every cord Wireless Power Transfer is proposed. The Coupled Mode Theory was theorized in 2006 and proven in 2007. Thus, magnetic and Electric Resonant Coupling allows power to traverse large air gaps with high efficiency. This technology is closely related to Electromagnetic Induction, antenna technology and resonator for the filters of communication technology. We have studied these phenomena and technologies using Equivalent Circuits- which is a more familiar and comprehensible format for electrical engineers than the Coupled Mode Theory. In this paper, we study maximum efficiency vs. air gap by Equivalent Circuit and propose simple equations about maximum efficiency of air gaps. The results of these equations are well matched with results from Electromagnetic Field Analysis.