Design of WPT coils to minimize AC resistance and capacitor stress applied to SS-topology

The only loss in the lumped circuit model of a wireless power transfer system comes from the parasitic resistances, which usually becomes more problematic at higher frequencies. Resonant currents and voltages can also exert a large stress on the system. This paper presents a simple coil design procedure that minimizes the AC resistance and the stress of the compensating capacitors. It results in the lightest coil designs that can be chosen from commercially available Litz wires. Test setup using SS-topology achieved 98.6 % coil-to-coil efficiency with 18 cm air-gap and 0.6 kg coils.