The impact of transfer medium on high-power inductive charging systems in mobility applications

Zilong Zheng

doi:10.17918/00010906

High-power inductive power transfer (IPT) systems operating in challenging environments--such as embedded beneath roadway surfaces or in conductive fluids--face significant electromagnetic losses that can reduce overall efficiency. This work provides a systematic investigation of power losses across multiple materials and scales, offering both fundamental insights and practical design guidance. A uniform-field laboratory study first analyzes the material losses in diverse pavement types, including hot mix asphalt (HMA) and various concrete formulations. Results show that dense-graded asphalt, exemplified by HMA-9.5 mm, consistently demonstrates lower power loss density compared to cementitious materials. In contrast, concretes with high porosity or polar admixtures exhibit greater electromagnetic attenuation, underscoring the importance of carefully choosing road materials for embedded IPT installations. The analysis is extended to underwater IPT, where saltwater's high conductivity and molecular polarity exacerbate loss mechanisms. Empirical models derived from a controlled solenoid-based test platform confirm that underwater losses scale strongly with frequency and flux density, surpassing air-based values by a substantial margin. These findings highlight the need for moderated operating frequencies or specialized coil designs to maintain viable efficiency in submerged charging applications. To validate the observations at high power, a full 18 kW IPT system--operating at 85 kHz in accordance with SAE J2954--is implemented. Embedding the transmitter coil beneath different pavement materials (e.g., HMA-9.5 mm, Portland cement concrete, and slag-based concrete) shows that asphalt's lower-loss characteristic persists at large scale, enabling DC-DC efficiencies above 95%. Surprisingly, increasing pavement thickness from 50 mm to 100 mm does not proportionally degrade performance; in some asphalt tests, thicker layers actually yield comparable or slightly reduced incremental losses. This outcome is attributed to near-field decay and asphalt's inherently characteristics, indicating that deeper coil burial can meet structural demands without incurring major efficiency penalties. Overall, the findings demonstrate that selecting appropriate pavement materials, optimizing coil geometry, and managing operating frequency are vital to mitigating power losses in both underground and underwater IPT. By blending empirical modeling with large-scale prototyping, this research guides future installations toward high-efficiency wireless charging solutions for electric vehicles, submerged robots, and other applications requiring reliable, contactless power delivery.

The impact of transfer medium on high-power inductive charging systems in mobility applications

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The impact of transfer medium on high-power inductive charging systems in mobility applications

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