Effects of twisting pitch on critical current of HTS tapes in Quasi-isotropic strand

Abstract

With the development of the second generation (2G) high temperature superconducting (HTS) tape, a several types of high current-carrying conductors have been proposed, among which the quasi-isotropic strand (Q-IS) can effectively improve critical current anisotropy. Twisting technology is essential in practical applications as it can effectively improve current uniformity and stability, reducing AC loss. Aiming at the structural characteristics of the Q-IS, this paper establishes a longitudinal strain model to describe the torsional strain of the tapes in the strand and studies the dependence of critical current characteristics on twisting pitch by theory and experiment. A set of twisting devices were designed, experiments were carried out on the tapes at three different positions in the Q-IS, and their critical currents under different twisting pitches were measured at 77 K. After comparing experiments, the results show that the longitudinal strain model can well describe the characteristics of the critical current of the twisting tapes in a Q-IS.