Influences of Ferromagnetic Deflectors Between Layers of Superconducting Power Transmission Cables on Transport Current Losses

Abstract

Alternating-current losses in two-layer power transmission cables constructed by type-II superconducting strips in the presence of ferromagnetic deflectors between the layers are numerically investigated. Each layer comprises 15 wires with rectangular cross section of 4 mm width and 2 μm height, while the inner and outer layer radii are 20 and 21 mm, respectively. Deflectors are composed of either non-magnetic or strongly ferromagnetic material, where the width and height of each is 5 mm and 80 μm, respectively. Losses are obtained through Finite-Element Method simulations with respect to amplitude of the applied current with 1 Hz frequency. Use of ferromagnetic deflectors increases the total alternating-current loss in the two layers considerably for small amplitudes, while the loss approaches that in non-magnetic case at amplitudes around the critical current. Individual layer losses are such that outer-layer loss is significantly larger, 2.5-fold at 1/16 of the critical current, for ferromagnetic deflectors, whereas they are almost identical in non-magnetic case at all amplitudes. Inner and outer wires are exposed to similar self magnetic fields of wires in non-magnetic case, while ferromagnetic deflectors accumulate magnetic field lines on themselves and increase the losses in outer wires. The current profile is homogeneous except at the edges of the wires in the non-magnetic case, whereas homogeneity is disrupted for the outer wire in the case of ferromagnetic deflectors, such that current flow in the positive direction is confined to the central region.