Research on quality factor of the coils in wireless power transfer system based on magnetic coupling resonance

The improvement of the coil quality factor results to a higher efficiency for wireless power transfer(WPT) system[1-3]. Additionally, adding a suitable magnetic core into the coil can effectively enhance the mutual inductance and improve the efficiency of WPT system[4-7]. The high frequency current is un-uniform in the wire due to the external magnetic field. As a result, the conductive area of the wire is much smaller than its cross-section, and the excess resistance, namely the frequency-dependent resistance, is induced. The frequency-dependent resistance is proportional to the squared field the wire exposed to[8-13]. Two simple models are built up for 3D Maxwell simulation to calculate the magnetic field. Maximum quality factor of coils and corresponding optimal operation frequency is derivate based on the analyzing of the field and resistance. Quality factor optimization by using the analytic method has been carried out and experiment for verification is done and the conclusions have been got.