Analysis of the Resonance Characteristics by a Variation of Coil Distance in Magnetic Resonant Wireless Power Transmission

Magnetic resonant wireless power transmission is a method that enables high-efficiency power transmission at a longer distance than the conventional magnetic inductive type. However, when the power transmission distance is smaller than a specific value, there is a problem that the frequency division phenomenon occurs and the output and efficiency decrease. In this paper, the equation of output power was formulated with transmission distance as variables and verified through simulation and experiments. After that, the resonance characteristics according to the transmission distance and the magnetic phenomenon in the frequency divided state were analyzed through the circle diagram and the finite-element analysis. From these results, it is possible to design the optimal system for the target transmission distance, and it is possible to calculate the split frequency representing the maximum power in short-range transmission, so that high output and efficiency can be obtained stably.