The potential of Roebel assembled coated conductor cables

Low ac-loss HTS cables for transport currents well above 1 kA are required for application in transformers and generators and are taken into consideration for future generations of fusion reactor coils. Coated conductors (CC) are suitable candidates for high field application at an operation temperature in the range 50-77 K, which is a crucial precondition for economical cooling costs. We prepared a short lengths of Roebel bar cables made from industrial DyBCO-CC (Theva Company, Germany) and YBCO-CC (Superpower). Meander shaped tapes of 4(5) mm width with twist pitches of 122(180) mm were cut from the 10(12) mm wide CC tapes using a specially designed tool. Eleven or sixteen of these strands were assembled to a cable. The electrical and mechanical connection of the tapes was achieved using a silver powder filled conductive epoxy resin. Ac losses of a short sample in an external ac field were measured as a function of frequency and field amplitude in transverse and parallel field orientations as well as the coupling current time constant in transverse field. The potential of this cable type for ac-use is discussed with respect to ac-losses and current carrying capability. (orig.)