Effects of bending strain on the critical current and AC loss of BSCCO/Ag tapes

When a coil or a winding is made, the superconducting tapes must be bent to different curvatures. Bending of high temperature superconducting (HTS) tapes can result in degradation of the critical current density and thus increase the AC losses of the tapes. Therefore, the effects of bending strain on the critical current and AC loss should be considered in the design of high temperature superconducting apparatus. In this paper, the dependence of critical current and AC loss on the bending diameter of the superconductor tape was experimentally investigated. The diameters of the curved tape were varied from 110 to 36 mm. AC loss measurements were taken at 77 K, 50 Hz. Analysis of the bending strain effects on the critical current and AC loss are presented. An expression describing the dependence of AC losses on bending strain is proposed by modifying Norris' formula. The experimental results are presented and compared with the calculated values.