Presentation Information
[WBP2-16]The Electric Field Dependence and Statistical Distribution Analysis of Critical Current for Superconducting Composite Conductors
*Yuto Yamaguchi1, GInta Utsunomiya1, Riichiro Tashiro1, Taketsune Nakamura2, Ryosuke Kubota3, Masayoshi Inoue1 (1. Fukuoka Institute of Technology (Japan), 2. Kyoto Univ. (Japan), 3. Fukuoka Institute of Technology Junior College (Japan))
Keywords:
High Temperature Superconductor,Superconducting Conductor,Critical Current,Statistical Distribution
In the squirrel-cage type high temperature superconducting induction/synchronous motors (HTS-ISM), HTS wires/tapes are applied to the end ring and the rotor bar. The rotor bars use composite conductors made from HTS tapes stacked by soldering. Therefore, the current-voltage (I-V) characteristic measurements of the HTS composite conductors are important. However, since the I-V characteristics are influenced by current paths caused due to the contact resistance and/or distance between the current leads and voltage taps, the apparent critical current (Ic) obtained by the standard electric field criterion (Ec=10^-4 V/m) may vary. In this study, we measured I-V characteristics up to an electric field range of more than two orders of magnitude higher than the standard electric field criterion for 49 conductors, and investigated the electric field criterion dependence and statistical distribution of Ic. In some conductors, the voltage begins to rise at current lower than the expected Ic. These conductors exhibited kink-behavior beyond approximately 10^-3 V/m, and then the n-value increased again. Therefore, we extracted Ic using two criteria of 10^-4 V/m and 10^-2 V/m, and obtained statistical distributions for each. Where the Ec was increased, the number of samples with low Ic values decreased, and a single dominant distribution was observed. We will discuss details of the I-V measurements and statistical analysis for the conductors in the presentation.