Modelling method for critical current of YBCO tapes in cable use

Superconducting YBCO cables are suitable to transfer large amounts of energy due to their small space requirements and low losses. The large energy transfer capacity is achieved by connecting several coated conductor (CC) tapes in parallel. The critical currents of the tapes will be changed when they are placed from self-field to the magnetic field of the cable. In this paper, the change was determined from the cable geometry and intrinsic J(c)(B)-dependence with fast and robust integral element method exploiting thin elements. The critical current distribution and the magnetic fields of 1 kA cable were computed. The so-called gap effect causes the critical current of the individual tapes to rise from 86.5 to 88.8 A when they are moved from the self-field to the cable field. The gap effect was studied as a function of width of the superconducting layers, cable radius and the number of the tapes. It was shown that the cable critical current can be given as a function of the tape number and the layer fill factor defined in this paper. In addition, the gap effect was studied as a function of zero field critical current density. The results suggest that up to 16% rise can be obtained with a cable of 25 tapes with critical current per tape width 500 A cm(-1). (c) 2007 Elsevier B.V. All rights reserved.