Circuit Coupling Model Containing Equivalent Eddy Current Loss Impedance for Wireless Power Transfer in Seawater

Nowadays, as the whole world put more emphasis on ocean resource exploration, the use of automatic underwater vehicles (UAVs) comes to be increasingly frequent. Inductive wireless power transfer (IWPT), as a power transfer solution with high safety and exibility, is quite promising applied in UAV power supply. However, when applied underwater, IWPT efficiency decreases due to eddy current loss (ECL) caused by high conductivity of water medium. In order to analyze IWPT output characteristics in seawater, this paper proposes a coupling circuit model involving equivalent eddy current loss impedance (EECLI), which is derived via three- coil model. On the one hand, it is found that splitting frequency still exists in IWPT under seawater. On the other hand, EECLI is independent to coil distance, but proportional to operation frequency. The validity of the proposed model for IWPT system with coils in small size (coil outer diameter 12 cm, system resonant fre- quency 570 kHz) is verified by experiment, which means it is available for IWPT system design and analysis.