A numerical study of power loss factors in resonant magnetic coupling

We numerically studied the affect of power loss factors in a wireless power transfer system using resonant magnetic coupling. Resonant magnetic coupling is regarded as one of the most promising methods for mid-range wireless charging systems. To make this method practical, it is important to accurately estimate power transfer efficiency and effect of each loss factor in the device-designing stage. We conducted a numerical simulation using an equivalent circuit model and electromagnetic analysis for a mobile-device model. Resonance at 7 MHz between the transmitting and receiving coils was achieved using lumped capacitors attached at the coil ends. In addition to the skin effect, we consider various loss factors such as proximity effect, loss tangent of lumped capacitors, and so on. The results show that the proximity effect significantly decreases the power transfer efficiency of the system, and the loss tangent of lamped capacitor also decreases it by a few percentage points.