Efficiency Characteristics of WPT System with Laminated Nanocrystalline Core Considering Nonlinear Factors Caused by Crushing and Compressing Process.

In order to reduce eddy current loss, nanocrystalline alloys used in wireless power transfer (WPT) system generally needs crushing and compressing process, which may lead to obvious nonlinear characteristics and affect both equivalent conductivity and permeability, thus impacts the transmission power and efficiency of WPT system. In this study, the effect of the nonlinear characteristics of the nanocrystalline on the maximum output power of WPT system without saturation at constant load is investigated by finite element analysis (FEA); and a method to determine the critical conductivity which can improve the efficiency of WPT system by adding nanocrystalline is proposed; meanwhile, the critical conductivity at different lamination coefficients are analyzed. Then, a selection method of nanocrystalline for WPT system is proposed considering the nonlinear characteristics and its laminated structure. Experimental validation was performed on 3-kW prototypes, the results show that nanocrystalline core with higher permeability saturates at lower currents, and the critical conductivity determination method is also verified. In addition, with identical initial permeability, the higher efficiency of magnetic coupler can be obtained by lowering lamination coefficient.