Design, Challenges, and Trends of Inductive Power Transfer Couplers for Electric Vehicles: A Review

The magnetic coupler is the heart of an inductive power transfer (IPT) system, which facilitates wireless power transfer through its air gap. The couplers are designed to maximize efficiency, power density, power transfer distance, and misalignment tolerance while minimizing leakage flux, weight, cost, and volume. The coupler design process becomes complex due to the nonlinear behavior of magnetics, sophisticated geometrical structures, and mandatory design limitations imposed by standards, such as SAE J2954/1, IEC 61980-1:2015, and ISO 19363:2020. Initially, this article reviews the advancements in coil design methodologies and their structures over the last few decades to identify the ongoing challenges and trends. The impacts of the power electronics system, industrial standards, material selection, numerical and analytical modeling methods, and thermal modeling on the coil design process are identified to formalize the design procedure. A coil design example based on finite element analysis (FEA) tools is presented to identify the drawbacks of the existing design and optimization process. A sensitivity analysis, 3-D-Pareto plots, and optimal design selection by considering misalignment variations are proposed to improve the multiobjective optimization process. A generalized guideline for coil design is proposed, which highlights the essential design stages of an IPT coupler. Current trends are identified, and future directions are proposed.