Transport AC Loss Characteristics of a Five Strand YBCO Roebel Cable With Magnetic Substrate

Transport AC loss in a short length of 5/2 YBCO Roebel cable (five 2 mm wide strands) with weakly magnetic substrate is measured. The AC loss data are compared with those for a single strand. All the strands composing the cable and the single strand are cut from the same stock material. Transport AC loss in the 5/2 Roebel cable is larger than that predicted by both the Norris strip and ellipse models over a large range of the cable current. The difference between normalized AC losses in the Roebel cable and the single strand is larger at low I_t/I_c than at high I_t/I_c, where I_t is the amplitude of transport current. These AC loss characteristics were not observed in transport AC loss results for YBCO Roebel cables composed of coated conductor with non-magnetic substrate. Results from an electromagnetic analysis of two parallel stacks of wire with magnetic substrate are presented to elucidate the results.