Analysis and experimental verification of three-coil inductive resonant coupled wireless power transfer system

In this paper, the basic principle of Wireless Power Transfer (WPT) based on resonance in magnetically coupled coils is described with detailed theoretical analysis of concepts. A novel approach of WPT is proposed using an additional coil between the main transmitter and receiver to enhance the transfer efficiency. The design process for the proposed WPT system is detailed, together with experimental investigation. Output voltages waveforms are presented for variable distances. Frequency domain analysis has been carried out for resonant frequency analysis and detection. It is observed that by using an intermediate coil between the transmitter and receiver coils, almost doubles the output voltage and improves the efficiency by more than four times of a two coil system. The effect of variable capacitors in the intermediate coil on the output voltage at different distances is experimented and founded that using a proper capacitor is required to achieve higher voltages. The output voltage can even be doubled if we use a proper capacitor.