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

摘要

Two types of four-layer cables composed of coated conductors, with practical cross-sectional geometries and various critical currents, were designed. The AC losses in the cables were numerically calculated using a numerical model employing a one-dimensional FEM (1D model). The AC loss of each layer in the four-layer cable with w = 4.0 mm was compared with Norris's analytical values, QNS, for a wide range of I-t/I-c. The AC loss in the first (innermost) layer was smaller than its QNS, whereas the losses in the outer layers were close to, or much larger than, their QNS. These results indicate that, in multi-layer cables, the AC loss in an outer layer increases because of the magnetic field generated by the current in the inner layers, and the entire AC loss of the cable is dominated by the AC losses in the outer layers. The AC losses in the four-layer cables with w = 3.3 mm, which had smaller gaps between the conductors, were smaller than those for the cable where w = 4.0 mm. These results showed the effectiveness of using narrower conductors and decreasing the gaps to reduce AC loss in multi-layer cables composed of coated conductors. The AC losses of the four-layer cable with w = 3.3 mm and I-cc/w = 500 A cm(-1) at 1 and 3 kArms were much smaller than the measured AC losses in cables fabricated with YBCO-coated conductors or BSCCO tapes. The AC loss in a four-layer cable with practical cross-sectional geometries should approximately be within an order of magnitude of their QNS.