Termination Methods for REBCO Tape High-Current Cable Conductors
Three types of joint termination methods for a 2G HTS cable have been developed: YBCO-BSCCO, YBCO-YBCO, and Folding-fan soldered terminations. For the YBCO-BSCCO terminator, each YBCO tape of a cable is connected to a BSCCO tape while the other ends of BSCCO tapes are bundled together and soldered inside a copper tube. The same termination was tested more than 30 times in liquid nitrogen and helium without any problems. It was operated at 10 kA in liquid helium and more than 2 kA in liquid nitrogen. The YBCO-BSCCO termination has been confirmed to be very easy to fabricate and convenient for a cable test since it is reusable. A YBCO tape termination method without BSCCO tape also has been proposed. Both terminations will be very useful for 2G HTS cables. These terminations are demountable if they are not soldered at the junction between tapes. Joint resistance is greatly reduced with increasing applied pressure especially for YBCO-YBCO contact joints. However, in the case of a YBCO-BSCCO joint, the BSCCO tapes may degrade at high pressure. The contact pressure should be optimized to obtain low joint resistance. If the contact surfaces of YBCO-BSCCO and YBCO-YBCO terminations are soldered for a permanent joint, the termination resistances are lower, and better uniformity will be achieved. Another termination is the Folding-fan termination. It is a soldered joint. Joint resistance distributions among cable tapes for these termination methods have been evaluated. Mechanical contact joint resistance distributions between YBCO-BSCCO tapes and YBCO-YBCO tapes have been measured under various contact pressures and contact surface conditions at 77 K. By optimization of the applied contact pressure and contact surface treatment techniques the contact joint resistance of a termination joint can be reduced and a better uniformity can be obtained. We also discussed effects on a cable performance due to no-uniformity of termination resistances, a loop resistance between two tapes in a termination of a cable, and a series operation of two 2G YBCO Twisted Stacked-Tape Cable (TSTC) conductors.
- Research Organization:
- Tufts Univ., Medford, MA (United States); Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States). Plasma Science and Fusion Center; Supercon, Inc., Shrewsbury, MA (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), Fusion Energy Sciences (FES); USDOE Office of Science (SC), Engineering & Technology. Office of Small Business Innovation Research (SBIR) and Small Business Technology Transfer (STTR) Programs
- DOE Contract Number:
- SC0004062; FC02-93ER54186; SC0007722; SC0004269
- OSTI ID:
- 1880222
- Country of Publication:
- United States
- Language:
- English
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