Inductance and Parasitic Capacitance Modeling of Spiral Air-core Inductor in MHz Inductive Power Transfer System

Air-core inductors are widely applied in high-frequency inductive power transfer (IPT) systems. However, its behavior at high frequencies is very different from that at low frequencies due to parasitic capacitance. In order to estimate the parasitic parameters of the air-core inductors at the design phase and avoid the designed inductors working at the capacitive range, this paper investigates the model of a spiral air-core inductor, including inductance and parasitic capacitance. Compared with previous models, which neglected the capacitance between non-adjacent turns, the proposed one considers all the turn-to-turn capacitance to obtain a more accurate result. The proposed model was verified by simulation and experimental measurement. The calculation, simulation, and measurement results are in good agreement. Compared to the measured results, the errors of the calculated inductance, capacitance, and self-resonant frequency are 2.0%, 7.4 %, and 4.1 %, respectively. Therefore, the proposed model is applicable to estimate inductance and parasitic capacitance for designing a better high-frequency air-core inductor.