Wireless power transfer using a superconducting capacitor

It has been demonstrated that a high temperature superconducting (HTS) wireless power transfer (WPT) system has the advantages of higher power transfer efficiencies and longer transmission distances. But the resistive losses of the conventional compensation capacitors, the copper connectors and the long copper connecting wires between the HTS coils in the liquid nitrogen and the conventional compensation capacitors outside still exist. Since at low frequencies the power transfer efficiency of a WPT system is dominated by the resistive losses (and at high frequencies by radiation) of the WPT system and the AC loss of superconductors is much lower than that of conventional conductors, using superconducting capacitors as the compensation capacitors is an optional way to further increase the power transfer efficiency. Here, a superconducting capacitor was constructed. Two kinds of HTS WPT experiments were conducted by use of the superconducting capacitor and the conventional capacitor as the transmitting compensation capacitor, respectively. The results are presented and analyzed. It is shown that though the capacitance of our superconducting capacitor changed a little, for the distance up to 1.5 times of the radius of the coils, the efficiency of the WPT system can be increased by 4.25% by using the superconducting capacitor as the transmitting compensation capacitor.