SE313864B - - Google Patents

Abstract

1030975 Super-conductive conductors SIEMENS-SCHUCKERTWERKE AG 13 April 1965 [17 April 1964] 15841/65 Headings H1A and A4D A hard super-conductor in which the critical current is raised by the application of a magnetic field parallel to the direction of current flow is formed as a wire which has been twisted about its own axis so as to become elastically deformed. Because of deformations caused by this process the current flows in helical paths in the wire, thus when the wire is super-conducting it can carry a higher current that it would if it extended simply along the axis. Alternatively, the hard superconductor may in the form of a plurality of untwisted wires forming a cable, each wire extending the full length of the cable and at least one of the wires being coiled helically about the axis of the cable. Suitable super-conductors are the alloys niobium-zirconium, molybdenum-rhenium, and tantalum-titanium. In an embodiment a coldrolled wire of a niobium-zirconium alloy containing 25% zirconium was twisted about its own axis. The twisting could have been combined with a drawing operation during manufacture of the wire. The wire may be annealed to remove strains set up during twisting. Such wires may be used in winding the outer coils of super-conducting magnet coils. They are less affected by transverse magnetic fields than are comparable non-twisted wires. The cable shown is made of seven identical strands. One extends along the axis of the cable, four more are wound as a coarse multi-start helix about the first, and the remaining two are wound as a fine double-start helix on the outside of the cable. The field set up by the outer strands has an appreciable component parallel to the direction of current flow in the strands of the inner helix which itself sets up a field substantially parallel to the current flow in the central strand. This cable can carry more current than a cable in which the strands all unparallel to the cable axis. Other cable constructions are suggested.