Numerical calculation of AC losses in multi-layer superconducting cables composed ofcoated conductors

Abstract

Two types of four-layer cables composed of coated conductors, with practicalcross-sectional geometries and various critical currents, were designed. The AC lossesin the cables were numerically calculated using a numerical model employing aone-dimensional FEM (1D model). The AC loss of each layer in the four-layer cable withw = 4.0 mm was compared with Norris’s analytical values,QNS, for a widerange of It/Ic. The AC loss in the first (innermost) layer was smaller than itsQNS, whereas the losses in the outer layers were close to, or much larger than, theirQNS. These results indicate that, in multi-layer cables, the AC loss in an outerlayer increases because of the magnetic field generated by the current inthe inner layers, and the entire AC loss of the cable is dominated by theAC losses in the outer layers. The AC losses in the four-layer cables withw = 3.3 mm, which had smaller gaps between the conductors, were smaller than those for the cable wherew = 4.0 mm. These results showed the effectiveness of using narrower conductorsand decreasing the gaps to reduce AC loss in multi-layer cables composedof coated conductors. The AC losses of the four-layer cable withw = 3.3 mmand Icc/w = 500 A cm−1 at 1 and 3 kArms were much smaller than the measured AC losses in cables fabricated withYBCO-coated conductors or BSCCO tapes. The AC loss in a four-layer cable with practicalcross-sectional geometries should approximately be within an order of magnitude of theirQNS.