Coil Design for Power Stability in WPT Based on Curve-Surfaced Characteristics

Power stability in wireless power transfer (WPT) systems is a key indicator for charging movable devices. It requires robust coil designs to achieve stable power delivery and high spatial freedom. However, coil designs tailored for irregular and confined spaces remain underexplored. This work investigates the characteristics of curve-surfaced coils, focusing on their capability to generate uniform magnetic fields and maintain stable cross coupling under varying spatial configurations. This study derives a theoretical model to analyze the mutual inductance between curved-surface transmitting coils and planar receiving coils. Design guidelines are established to enhance performance in scenarios involving lateral or rotational misalignment. To validate the proposed method, a 6.78 MHz WPT system is implemented and tested. The experiment results confirm that the proposed coil design achieves stable power transfer and high spatial flexibility, demonstrating its potential for practical applications.