A wireless power transfer system for electric vehicles is required to have high efficiency, a large air gap, and good tolerance for misalignment in the lateral direction and to be compact and lightweight. A new 3 kW transformer has been developed to satisfy these criteria using a novel H-shaped core and split primary capacitors. The design procedure based on the coupling factor k, the winding's Q, and the core loss is described. An efficiency of 90% was achieved across a 200 mm air gap.

A wireless power transfer system for electric vehicles has to deal with the issue of high leakage levels of electric field. In this paper, we propose two methods for reducing the leakage electric field. First is the use of ferrite to reduce the emitted leakage electric field to the environment. Second is the changing of the pulse width of the inverter to reduce the harmonics of leakage electric field. We present the experimental results of the reduction effects of leakage electric field. We also compared the leakage electric field using seriesparallel and series-series resonant capacitor topologies.