Analytical Formulation of $I_{c}$ Dependence on Torsion of YBCO and BSCCO Conductors

The behavior of HTS tapes under torsion is of key importance for the definition of the allowable twist during cabling activity. In this paper, we report on the elaboration of self-consistent analytical expressions of I_c dependence on twist pitch for YBCO and BSCCO (2223) conductors. The computed expressions are validated with the results of a series of tests performed at 77 K and in self-field with a purpose-built setup. The I_c was observed to be reduced to 95% of the unstrained value for twist pitches of 114 mm for BSCCO tapes, and 80-90 mm for YBCO tapes. The reduction of performance was identified to be caused mainly by irreversible degradation of I_c at the tapes edges. At lower temperatures, a slightly lower sensitivity to twist is expected.