Substrate and stabilization effects on the transport AC losses in YBCO coated conductors

In support of second generation HTS conductor development for ac applications, transport ac loss measurements were conducted on a series of RABiTS-processed YBa₂Cu₃O_x (YBCO) coated conductors with different nickel alloy substrates and copper stabilization at 77 K. Each 1-cm wide sample had a critical current density between 1.0 and 2.0 MA/cm² and had either a 75 μm Ni-5at%W substrate or a 75 μm Ni-10%Cr-2%W substrate with 2-μm nickel overlayer. Samples with copper stabilization had a 50-μm strip of 1 cm wide copper laminated to a 3-μm thick silver coated YBCO sample. Using thermal and electrical measurement techniques, the ac losses were measured as a function of the peak current ratio at 60 Hz. Experimental results were compared to the Norris thin strip and elliptical models to determine the influence of the ferromagnetic loss of the substrate and the copper lamination on the total ac loss.