A design methodology for multi-kW, large air-gap, MHz frequency, wireless power transfer systems

In a loosely coupled kW level wireless power transfer system, it is difficult to consider multiple design considerations simultaneously because of the system complexity. Circuit design methodology is critical to achieve efficient, low VA rating, and stable system. In this paper, a design methodology for a loosely coupled series-parallel resonant system is proposed. Proposed design methodology is evaluated by a 3kW, 30cm distance power transfer design example. Using the methodology, efficiency, VA rating, stability, and safety issues are considered simultaneously. The example model is implemented by means of FEA. A surface spiral winding transmitter coil is used in the FEA model. Quality factor (Q) dependence of surface spiral winding on mechanical design parameters is investigated to maximize the Q. Based on the investigation, a high Q coil is designed for the system and the coil is used as a transmitter to evaluate the proposed methodology.