Size-adjustable Coils for Compensation of Lateral Misalignment in WPT Systems

This work demonstrates the feasibility of size-adjustable coils to minimize the reduction of the transfer efficiency due to the lateral misalignment between the source and load coils in a resonant-type wireless power transfer system. Experimental results for a 6.78 MHz system reveals that by reducing the size of the coil adaptively according to the misalignment, the transfer efficiency can be maintained above 80% even when effective overlapping area is reduced to 11.5% between a 20 × 20 cm² coil pair. Moreover, the proposed coil system successfully removes the transfer null caused by a large misalignment. The proposed virtual system is expected to maintain the transfer efficiency higher than 40% even when the misalignment is such that one coil is completely outside the other.