Application of sinter-forged Bi-2223 bars to 1500-A a.c. power utility service as high-frequency current leads in a 77-4 K temperature gradient
✍ Scribed by U. Balachandran; C.A. Youngdahl; M.T. Lanagan; S.E. Dorris; J.J. Picciolo; J. Cluff; T. Brent; M. Marinelli; B. Fisher; P. Winandy; J. Wenzlaff; T. Askew; R. Niemann; R.B. Poeppel; M. Nakade; T. Hara
- Publisher
- Elsevier Science
- Year
- 1995
- Tongue
- English
- Weight
- 669 KB
- Volume
- 3
- Category
- Article
- ISSN
- 0964-1807
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✦ Synopsis
Two assemblies of Pb-BSCCO 2223 superconductor bars were produced for use in ac connections between utility system lines at room temperature and a fault-current limiter operating at 4 K. Each assembly, consisting of four parallel bars arranged within a 100 mm-diameter-boundary, delivered 15;OO A (peak), 50-60 Hz ac through the 774 K range of the temperature gradient while dissipating .< 0.3 W. The sinter-forged bars displayed dc critical current densities of 950-1300 A cm-* at 77 K and > 5000 A cm-' at 4 K; magnetic field sensitivity was relatively small. Although thermal conductivity tests showed values much higher than those found in the literature for polycrystalline Pb-BSCCO 2223 made by other processes, this undesirable result was counterbalanced by the relatively high values of critical current, which enabled the use of bars with smaller cross-sectional areas. Typical 50-Hz ac power losses at 77 K in each bar (with a cross-sectional area of 0.54 cm') were 1 mW cm-' of length at 310 A and 1.75 mW cm-' at 375 A. Losses were much smaller at 4 K. Bars were 25 cm long, including ends that carried silver contacts sinter forged to the ceramic, with a 21 cm silver-free length in the thermal gradient between the fixed-temperature terminals. Thermal efficiency of the assemblies was assessed by helium boiloff tests.