Impact of local geometrical irregularities on critical currents of REBCO tapes in round cables

Abstract

Abstract REBa2Cu3O7-x (RE—rare earth, Ba—barium, Cu—copper, O—oxygen) tapes used in common multilayer superconducting cables, such as Roebel cable, twisted stacked tape cable or vonductor on round core/tube (CORC ® /CORT), undergo shape modifications during the cable production. In particular, the tapes edges are regularly raised due to the Poisson effect during bending of tapes in the cable assembling process. This kind of deformation amplifies the local strain in subsequent layers, endangering the capability to transport electrical current. We explore such deformation by numerical and analytical calculations validated by experiments. Three-point bending device submerged in liquid nitrogen was developed for this purpose. We found that, if the orientation of Poisson effect deformations is along the tape length, the local strain is reduced and performance of the cable remains unaffected. In contrary, the local deformations at the crossings of tapes from subsequent layers represent a serious threat towards reaching a satisfactory critical current retention.