Electrical degradation of a high-Tc superconductor by continuous current transport

Several companies in the world are marketing superconducting products, such as wires, films, and bulk, and so on. High-T_c superconducting (HTS) systems have begun to be commercialized with these HTS products, and the demand for them is increasing. A database on the electrical degradation of high-T_c superconductors is an essential requirement to commercialize HTS systems. The electrical degradation of Bi-2223 wire has been investigated in this paper. To simulate the conditions of real systems, two types of specimens were prepared. One was named Ring Specimen with Bi-2223 wire on a bobbin of 400 mm diameter and the other was named Double-Pancake Specimen with Bi-2223 wire coiled on a bobbin of 100 mm diameter. The Bi-2223 wire of the Double -Pancake Specimen was coiled with several winding tensions. The continuous current transport method was used for the measurement of the electrical degradation. Various levels of transport current were applied to each conductor. The levels are 90, 95, 98, and 110% of the critical current (I_c) in Ring Specimens and 95 and 150% in Double-Pancake Specimens. Although a difference of the I_c in the long Bi-2223 wire was found, there was not any severe degradation in the Ring Specimens. When the level of transport current was below the critical current, degradation did not appear in the Double-Pancake Specimens either. However, they degraded very quickly when the level of transport current was 150% of I_c.