Magnetization loss measurements of Bi-2212 round wires fabricated by stranded-and-formed method

Round high Tc superconducting wires are sometimes preferred to flat tapes, because they are easy to assemble to obtain large current carrying capacity, and their performance in the external magnetic field is isotropic. Ag- or Ag/Au-sheathed Bi-2212 round wires were fabricated by the stranded-and-formed method. In this method, first, 54 filaments are bundled to make a segment, and then, three segments are stranded, drawn, and formed to a final round-shape wire. Advantages of the round wires fabricated by the stranded-and-formed method include higher tolerance against bending strain and higher critical current density than usual round wires. Another potential advantage of this type of round wires is the reduction of AC losses due to their multiply twisted structures. The magnetization losses of four types of the Bi-2212 round wire with multiply twisted structure were measured. The effect of the multiply twisted structure for the AC loss reduction was confirmed by the experimental results.