Magnetization ac loss reduction in HTS CORC^®cables made of striated coated conductors

Abstract

High temperature superconductors (HTSs), like for instance REBCO (RE=rare earth) coated conductors, are of high potential for building large superconducting magnets. Some magnets, such as accelerator magnets, require the use of superconducting cables to allow fast ramping, and low magnetization loss to mitigate field quality issues. One of the methods to lower ac loss is to divide the superconducting layer in the tape into filaments. In this paper, conductors with copper stabilization for practical applications are laser scribed into narrow filaments. Striated tapes are then wound into conductor on round core (CORC ® ) cables. The critical current and magnetization ac loss of single tapes were measured. We found that the stabilizing copper layer causes difficulties for laser scribing. The degradation of the critical current is more pronounced than in the case of non-stabilized tapes. The selection of the number of filaments is therefore a compromise between critical current degradation and reduction of ac loss. Based on the results obtained from single tape experiments, the optimum number of filaments in 4 mm wide tapes was chosen, and CORC ® cables with 2, 3 and 4 layers of tapes with and without filaments were manufactured. Magnetization ac loss measurements at 77 K showed a reduction of ac loss in the cables with filaments. This reduction corresponds almost to the number of filaments. Measurement at different frequencies also showed that the coupling loss in CORC ® cables with a short twist-pitch is relatively small in comparison to hysteretic loss.

Strain Distribution in REBCO-Coated Conductors Bent With the Constant-Perimeter Geometry

“…If the assumption holds, small winding angles (longer pitches) are favored for a helical tape configuration as they reduces the axial strain, as shown by (10). This assumption is supported by the experimental results on helically wound tapes in tension [18] and compression [50].…”

Study of the magnetization loss of CORC® cables using a 3D T-A formulation

“…In order to validate the model, AC losses were calculated and compared to those published in [38]. The geometrical and physical properties were chosen in accordance with [38], as shown in Table 1. Two CORC cable samples are wound from REBCO tapes, which are named as Cable B and Cable C. Cable B has two layers and each layer is wound with 3 tapes.…”

“…A laser scribing technology has been applied on REBCO tapes to reduce AC losses, in which the superconducting layer of the tape is divided into filaments by laser scribing and meanwhile the substrate layer is kept for a mechanical support [38,42]. This section focuses on the magnetization loss reduction using striated tapes for CORC cables.…”

“…Simulations are performed on the striated counterparts of Cable A and Cable B, and the effect of filaments on magnetization loss is shown in Figure 12 and Figure 13. Here, to apply a simple variable method on the filament, the critical current of all the filaments is assumed uniform, the trench between filaments is neglected and the critical current reduction generated by the tape striation is neglected, though the critical current of REBCO tape shows a significant degradation when the number of filaments is more than five [36][37][38]59]. The coupling current between individual filaments is neglected by constraining the total current of each filament to be zero in the calculation.…”

AC Loss Comparison Between Multifilament and Nonstriated YBCO Coils Designed for HTS Propulsion Motors

“…A great number of research groups as well as manufacturers have been focusing on investigating the magnetization AC loss and transverse resistivity of striated tapes [3][4][5][6][7][8]. Lots of researchers has confirmed that striation is an effective way to reduce the hysteresis AC losses.…”