Berlin 2008 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 10: Superconductivity: Fabrication and Characterization

TT 10.2: Vortrag

Montag, 25. Februar 2008, 14:15–14:30, H 3010

Roebel Assembled Coated Conductor Cables (RACC): Ac-Losses and Application Potential — •Curt Schmidt and Wilfried Goldacker — Forschungszentrum Karlsruhe, Institut für Technische Physik

High temperature superconducting (HTS) cables for transport currents well above 1 kA, assembled from a number of tapes, are required for application in transformers, generators and for future fusion reactor coils. Coated conductor (CC) tapes are suitable candidates for an operation temperature between 50 and 77 K which is a crucial precondition for economical cooling costs. Ac-field applications require low ac-loss cables and hence transposition of the individual tapes. The in the plane inflexibility of the tapes doesn't allow classical twisting techniques. The problem can be solved using a modified Roebel technique where meander shaped tapes are assembled to a Roebel cable. The electrical connection between the tapes, necessary to allow current redistribution, and the mechanical stability is achieved by impregnation with a conductive epoxy resin. We prepared short lengths of cables with 11 and 12 structured tapes and measured ac-losses in an external ac field and coupling current time constants. In the interesting frequency range below 100 Hz the coupling losses are small compared to hysteresis losses in the tape. The possibility of hysteresis loss reduction by striating the tapes should therefore be taken into consideration. Finally we discuss the potential of this cable type with respect to ac-losses and current carrying capability as a function of operation temperature, as well as possible routes of long length cable fabrication.