A wireless power transfer system with a double-current rectifier for EVs

The secondary coil installed on an EV is required to be small in size, light in weight, and efficient in power transfer, as well as tolerant in lateral misalignment with a large air gap. Also, a wireless power transfer (WPT) system needs high power transfer. Both downsizing and high power transfer bring a thermal problem the secondary coil. This paper proposes a WPT system combining the so-called "series and series" connected resonant capacitors with a double-current rectifier to achieve a secondary coil current reduction that is an essential matter of the problem. The proposed WPT system employs solenoid coils that are superior to circular coils in terms of misalignment and flux-distribution performance. The secondary WPT coil rated at 18 A is designed, constructed, and tested to verify the principles of operation. The system efficiency is 90.0% at nominal air gap 135 mm without misalignment in output power 7 kW.