A Novel Modeling and Design Method of Ferrite Pads to Enhance Comprehensive Performance in 11.1 kW Inductive Power Transfer System

Magnetic core parameters critically determine the transmission efficiency, power density, and overall performance of inductive power transfer systems. Conventional pad design methods predominantly rely on global optimization using simulation tools, often lacking clear physical interpretation. This study identifies a performance threshold for magnetic pads, beyond which further improvements in pad performance yield no meaningful gains in transmission efficiency. To quantify this threshold, an analytical model based on the boundary distribution of magnetic vector potential is developed, replacing conventional source-driven field approximations. The proposed formulation characterizes the internal magnetic field distribution and enables accurate determination of the threshold for magnetic pad sizing. Based on this insight, a sizing strategy is introduced to significantly enhance power density while maintaining high transmission efficiency. The method is validated through coupled electromagnetic–thermal simulations and experimental tests across a power range of 3–11.1 kW. Results show that, compared with an oversized reference pad—with a 25% increase in side length and a 56.2% increase in area—achieving only a 0.6% improvement in AC-AC transmission efficiency, the optimally sized pad improves efficiency by 3% over a downsized pad, which has a 25% reduction in side length and a 43.8% decrease in area, while also reducing peak temperature by 10°C. These findings validate the proposed method's effectiveness in improving system power density and optimizing magnetic– thermal performance without compromising transmission efficiency.