Charging Characteristics of Rotary HTS Flux Pump With Several Superconducting Wires

High-temperature superconducting (HTS) flux pumps are used to charge HTS coils at cryogenic temperatures without thermal and mechanical contact with the power supply at room temperature. We found that the larger the alternating magnetic field (AMF) penetrating into the HTS wire, the faster is the current charge rate in the HTS coil and the larger will be the amount of charge. AMF causes vortex pinning of the HTS wire to move, resulting in dynamic resistance ( R dyn ) and electromotive force (EMF). Charging characteristics are determined by R dyn and EMF which are generated by effective internal resistance ( R eff ) and open-circuit voltage (OCV), respectively. Even if AMF of the same magnitude penetrates the wires, the size of R eff and EMF generated will vary depending on the characteristics of the HTS wires. Therefore, in this study, R eff and OCV of a HTS wire are measured and compared with the results of HTS coil charging using a flux pump.