Multiple-Split Transmitting Coils for Stable Output Power in Wireless Power Transfer System with Variable Airgaps

In this paper, a tunable multi-split transmitting (TX) coil for a wireless power transfer (WPT) system that accommodates a wide range of distances between the TX and receiving (RX) coils is proposed. This method enables the WPT system to maintain a stable and consistent output power supply to the load, regardless of variations in coupling coefficients caused by changes in the distance between the TX and RX coils. The tunable multi-split TX coil can operate in various modes depending on how the wire connections between each TX coil are configured. This approach adjusts the inductance value of the TX coil for different conditions, using the same amount of coil as a conventional single-loop TX coil. The results show that by adjusting the TX coil to three different modes as the airgap varies from 50 mm to 250 mm, consistent output power is achieved with smaller variations in the input current and voltage compared to those in a conventional system. A conventional system requires an input voltage increase of approximately 529.64%, while the proposed system requires only a 42.93% increase. The proposed system enhances the power transfer capacity of the WPT system, particularly when operating in an over-coupling state. This approach provides a stable output power supply with a standardized and simplified TX coil structure.