Transport and magnetization ac losses of ROEBEL assembled coated conductor cables:measurements and calculations

Abstract

Many superconductor applications require cables with a high current capacity. This is notfeasible with single-piece coated conductors because their ac losses are too large. Therefore,it is necessary to develop superconducting cables with a high current capacity and low aclosses. One promising solution is given by ROEBEL cables. We assembled three ROEBELcables from commercial YBCO coated conductors. The cables have the same width but adifferent number of strands, which results in different aspect ratios and currentcapacities. We experimentally studied their ac losses under a transport current or aperpendicular magnetic field. In addition, we performed numerical calculations,which agree with the experiments, especially for the transport case. We foundthat in the cables there is good current sharing between the strands. We alsofound that stacking the strands reduces the magnetization losses. For a givencritical current, thicker cables have lower magnetization ac losses. In addition, aconducting matrix is not required for a good current sharing between strands.