Evaluation of power transmission and effect of air gap in waterproof sealed case for magnetic field resonance wireless power transfer

Abstract

　In this study, the transmission property of undersea magnetic field resonance type wireless power transfer (WPT) is reported. It is necessary to use a waterproof sealed case because transmission efficiency of the electricity decreases when a coil is wetted with water or seawater. A 30 turns, 160 mm diameter coil is prepared. We put the coil used as a resonator in a waterproof sealed case, and the coil is resonated and tested. From experiment results, we achieved 80mm WPT and transmitted 6 W. Frequency around 0.85 MHz is suitable for undersea WPT. We experimentally found that the optimal thickness of the air gap between the coil in the waterproof case and the wall surface of the case is around 20 mm.