Review of Coupled Magnetic Resonance System (CMRS)

Abstract

In this chapter, the well???known coupled magnetic resonance system (CMRS) is explained, stating that it is nothing but new and is a sort of conventional inductive power transfer system (IPTS). There are three major magnetic couplings between coils in CMRS: source???transmitter (Tx), Tx???receiver (Rx), and Rx???load couplings, respectively. Except for Tx???Rx coupling, other couplings do not directly contribute to wireless power transfer. Hence, this miscellaneous coupling can be replaced with a lumped transformer with a ferrite core. Because there is only a Tx???Rx coupling, the CMRS becomes compact in size and robust to ambient changes. Moreover, the design of CMRS is drastically simplified without complicated multiresonance tunings due to a small magnetic flux linkage from the source coil or the load coil.Coreless coils are used for Tx and Rx coils to examine the characteristics of CMRS with lumped transformers. A detailed static analysis on the explicit circuit model of the proposed CMRS and design procedures are fully established. Experiments for 1 W and 10 W prototype CMRSs with a class???E inverter at the switching frequency of 500 kHz, where the quality factors are less than 100, verified the usefulness of the proposed model, achieving 80% of the maximum Tx coil???to???load efficiency. It is concluded that the conventional CMRS, in general, is just a special form of IPTS where the quality factor is extremely high with coreless Tx and Rx coils.This chapter is based on two papers, one by B.H. Choi, E.S. Lee, J. Huh, and C.T. Rim, ???Lumped impedance transformers for compact and robust coupled magnetic resonance systems,??? IEEE Trans. on Power Electronics , vol. 30, no. 11, pp. 6046???6056, November 2015 and the other by J. Huh, W.Y. Lee, S.Y. Choi, G.H. Cho, and C.T. Rim, ???Frequency???domain circuit model and analysis of coupled magnetic resonance systems,??? Journal of Power El ectronics , vol. 13, no. 2, pp. 275???286, March 2013.