Effects of coil parameters on transfer efficiency in LCL wireless power transfer system

The transfer efficiency of WPT system is affected seriously by the AC internal resistance of power coils, the transverse offset and the separation distance between coils. Sometimes the user sets the tolerance of the relatively larger transverse offset as the primary aim, but they never give up high efficiency. This paper theoretically analyzes the effects of the ratio between AC internal resistance of coil and mutual inductance on the transfer efficiency in the LCL WPT system, and then, we get the minimum permitted value of the mutual inductance with specific efficiency in a given WPT system. In addition, we also get the permitted degree of the transverse offset under different separation distance between coils. Finally, we find that decreasing the AC internal resistance is beneficial to increasing the transverse offset. Experimental results verify the theoretical analyses.