Transmission Characteristics Analysis of Underwater Three-Coil WPT Systems under Various Misalignment Conditions

This paper examines the transmission characteristics of underwater three-coil Wireless Power Transfer (WPT) systems under various misalignment conditions. A circuit model for the three-coil WPT system is established to identify key electrical parameters influencing performance. Through simulation and experimental analyses, the effects of different misalignments on system's transmission characteristics are quantitatively evaluated. The results reveal that horizontal offsets negatively affect the efficiency of the three-coil WPT system, with the adverse impact on system efficiency increasing progressively when the misalignment occurs in the receiving coil, relay coil, and transmitting coil, respectively. The system maintains over 70% efficiency within a horizontal offset of 70 mm. Additionally, it shows strong resilience to coaxial rotational offsets, with efficiency fluctuations kept below 5% under a 30° rotational misalignment. These findings demonstrate the robustness of the underwater three-coil WPT system, highlighting its suitability for practical applications where alignment variations are inevitable.