Improvement in Power Transmission Efficiency of Wireless Power Transfer System Using Superconducting Intermediate Coil

We have demonstrated that using a high-quality-factor intermediate (IM) coil with a high temperature superconductor (HTS) wire improves the power transmission efficiency (PTE) of a wireless power transfer (WPT) system for long-distance power transmission. The IM coil is placed at the center of Cu transmitting (Tx) and receiving (Rx) coils and consists of a previously developed double-sided HTS coated conductor (CC) wire. A WPT system with the HTS IM coil was designed on the basis of the design theory for a third-order bandpass filter. The measured PTE of the system was compared with that of one with a Cu IM coil. The resonant frequencies of the Tx, Rx, and IM coils in both systems were each about 9 MHz. When the distance between the Tx and Rx coils was 160 cm, the PTEs of the systems were 49.7% and 17.5%, respectively, demonstrating that the PTE of a WPT system can be greatly improved by using an HTS IM coil rather than a Cu one.