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

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

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Abstract

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 1500 A (peak), 50-60 Hz ac through the 77-4 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-2 at 77 K and > 5000 A cm-2 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 cm2) were 1 mW cm-1 of length at 310 A and 1.75 mW cm-1 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.

Original languageEnglish (US)
Pages (from-to)313-320
Number of pages8
JournalApplied Superconductivity
Volume3
Issue number6
DOIs
StatePublished - Jun 1995

All Science Journal Classification (ASJC) codes

  • Engineering(all)
  • Physics and Astronomy(all)

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