Current and Field Distribution in Meandered Coated Conductors for Roebel Cables

Alternating currents or fields in coils, transformers or generators may lead to high losses in superconducting cables. The main contributions to these ac-losses are hysteresis losses of the superconductor and coupling losses between the strands. The hysteresis losses can be reduced by decreasing the width of the tapes. The resulting smaller cross section of the individual filaments could lead to a strong reduction in performance, if the tape is not homogeneous and the current cannot flow around local defects any longer. Hence, detecting local defects before cutting and assembling becomes very important. With our scanning techniques, we visualize the field penetration and the current flow within different two-dimensional structures like Roebel strands. The effect of different local defects on the current distribution in Roebel single strands is examined. Direct measurements of the conductor performance with respect to its geometry are important for finding the best solutions for future cable designs.