A critical review of electromagnetic coil assembly design and optimization for wireless power transfer in electric vehicles: Technical insights

Wireless power transfer (WPT) provides a cable-free solution for charging electric vehicles (EVs), with the electromagnetic coil assembly playing a key role in energy transfer efficiency. This paper critically reviews coil and coupler design methodologies for WPT, emphasizing their influence on system performance, including efficiency, misalignment tolerance, and safety. Despite progress, achieving efficiencies above 90% over distances exceeding 150 mm remains challenging, alongside managing electromagnetic interference (EMI) and addressing performance gaps that hinder widespread adoption. The study evaluates coil geometries circular, rectangular, spiral, helical, 3D-printed, and resonant, focusing on mutual inductance, coupling coefficients (e.g., k>0.5), and misalignment tolerance, complemented by optimization techniques like genetic algorithms and artificial intelligence (AI). Recent advancements in high-conductivity materials, ferrite shielding, and metamaterial integration are assessed, emphasizing practical trade-offs like manufacturability and safety at high power levels (>11 kW). Experimental insights from prototypes (e.g., 1.5 kW at 97.6% efficiency) highlight unresolved issues, including standardization and thermal management under high-frequency operation. This work synthesizes current insights and outlines future research directions to guide engineers and researchers in advancing WPT coil design for EV applications.