Universal Eddy Current Loss Modeling for Seawater WPT Systems via Pattern Extraction and Curve Fitting

The model of eddy current loss (ECL) is essential for guiding its suppression in seawater WPT systems. This paper proposes a pattern extraction and curve-fitting method for modeling ECL in coupled coils with magnetic cores. The model is universal and accurately captures the relationship between WPT systems and eddy current resistance (ECR). Specifically, it provides a precise expression for mutual resistance, facilitating both its calculation and measurement. A circuit model of the seawater WPT system is developed, with its accuracy, particularly regarding the impact of mutual resistance on ECL, validated using LCC/S, S/SP(C), and S/SP(L) systems. The results indicate that, compared to the LCC/S system, the mutual resistance in the S/SP(C) system, where the coil current phase difference is significantly greater than 90<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^{\circ }$</tex-math></inline-formula>, effectively suppresses ECL. Conversely, the S/SP(L) system, with a phase difference significantly less than 90<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^{\circ }$</tex-math></inline-formula>, exacerbates ECL. An experimental setup simulating seawater with a conductivity of 5.0 S/m is built. At a transmission distance of 15 cm and an operating frequency of 85 kHz, the efficiencies of the LCC/S, S/SP(L), and S/SP(C) systems are 84.3%, 72.9%, and 90.0%, respectively, with the efficiency gap widening at higher frequencies.