Design of High-Frequency Current Transformer for Capacitive Wireless Power Transfer Systems

Capacitive wireless power transfer systems operate near their resonant frequency, typically in the MHz range, with high-quality factor (Q) ensuring sinusoidal currents in the passive elements. High-Frequency Current Transformers (HFCTs) are ideal for sensing such high-frequency currents. However, designing an HFCT for a specific measurement bandwidth presents challenges due to the influence of various design parameters on its performance. While there are advanced commercially available current sensors with high bandwidth, such as Tell-i current sensors and Combinational Rogowsky coils, these options are prohibitively expensive. This paper proposes a methodology for designing a low-cost HFCT for high-frequency sinusoidal current measurement to address this research gap. The proposed procedure facilitates a quick and straightforward comparison of different magnetic materials based on their complex permeability (μ), enabling the selection of the most suitable material for the design and, ultimately, the design of the HFCT. The finalized HFCT is then used to measure the sinusoidal resonant current of a series RLC circuit, and the measurement results are compared with analytically calculated data.