Effects of the Number of Layers and Air Gap on Efficiency, Impedance, and Power Transfer in Multilayer Resonant Wireless Power Transfer Systems
IEEE Access, 2026 (SCI-Expanded, Scopus)
- Yayın Türü: Makale / Tam Makale
- Basım Tarihi: 2026
- Doi Numarası: 10.1109/access.2026.3737561
- Dergi Adı: IEEE Access
- Derginin Tarandığı İndeksler: Science Citation Index Expanded (SCI-EXPANDED), Scopus, Compendex, INSPEC, Directory of Open Access Journals
- Anahtar Kelimeler: cascaded resonance, Litz wire, mode splitting, multi-layer WPT, Wireless power transfer
- Van Yüzüncü Yıl Üniversitesi Adresli: Evet
Özet
This paper presents a systematic experimental and theoretical study of the effects of layer count (two to six) and inter-coil air gap (50–400 mm) on efficiency, impedance, and power transfer in a cascaded resonant wireless power transfer (WPT) system designed for kilowatt-level operation across the 63–87 kHz frequency band. Across 17 layer–spacing configurations, each coil is individually tuned to resonance via a dedicated series compensation capacitor, forming a fully resonant chain through which magnetic energy is transferred progressively from transmitter to receiver — in contrast to conventional two-coil architectures. To support this experimental investigation, a complete 6×6 impedance matrix formulation incorporating nearest-neighbor coupling is developed for the most general, heterogeneous six-layer configuration of the coil chain (L: 118–718 μH, C: 5–30 nF); generalized eigenvalue analysis of this formulation yields six resonance modes spanning the 63–149 kHz range, of which three fall within the experimental operating band and agree with measured resonance peaks to within 1.0 kHz. The relationship between coupling-coefficient distribution and mode-splitting behavior is quantitatively established: asymmetric inter-coil spacing produces non-uniform eigenmode spacing, with the three in-band modes (f1–f3) confined to the 64–79 kHz sub-band and f₄ pushed to 90.45 kHz by the stronger coupling in the lower stack. Experimentally, kilowatt-level operation exceeding 90% efficiency is demonstrated: a peak efficiency of 91.11% is achieved at three-layer, 150 mm spacing, 84 kHz, while a maximum output power of 1,149.52 W is recorded at two-layer, 100 mm spacing, 78 kHz. A systematic comparison across all 17 configurations reveals that maximum efficiency and maximum output power do not coincide under the same operating conditions, and that this trade-off depends systematically on layer count, providing practical design guidance for multi-layer WPT systems.