Development of YBCO Roebel cables for high current transport and low AC loss applications

Abstract

We discuss production of lengths of up to 27 m of YBCO Roebel cable. Results for 5/2 (5 strands, 2 mm width), 9/2 and 15/5 cables produced from standard 12 mm commercial YBCO wire are presented. We discuss specifications for the input wire and suggest using a statistical correlation function, using data from magnetic field scanning, that is shown to produce high performance strands. We discuss advances in manufacturing techniques including cable insulation processes. Transport and magnetic AC loss data are presented for 5/2 cable which demonstrates the effectiveness of decreased strand width and the transposition of strands. Both losses are predominantly hysteretic in nature. Finally, the cable DC transport is presented and we discuss the possibilities for high current cables in high field applications.

Current carrying capability of HTS Roebel cable

“…We adjust the parameters manually until a reasonable fit to the J c (B ext )-dependence of our constituent YBCO cable strands is obtained. We manufacture these strands from commercial YBCO wire [5]. The parameter values we find to match the normalised field dependence are; B 0 = 25 mT, a = 0.65 and c = 3.…”

“…For HTS applications the current capacity of given wire at different temperatures and fields, I c (B, T, H), is usually scaled from 77 K, self-field, values. For HTS Roebel cable, composed of multiple strands of conductor, the 77 K critical current is strongly affected by the self-field [3][4][5]. To design devices using Roebel cable it is useful to understand the effect of self-field on the 77 K measurement in some detail.…”

Magnetization Losses of Roebel Cable Samples With 2G YBCO Coated Conductor Strands

“…LTERNATIVE CABLING technology is required for constructing cables with transposed strands using high temperature superconducting (HTS) flat tapes, a necessary geometry for attaining high critical current density by texturing Roebel cables [1], originally invented more than a hundred years ago for reducing ac loss in conventional machines, is a promising configuration which have received considerable research and development effort for adapting to HTS conductors [2][3][4]. While the initial driver for HTS Roebel cables has been the reduction of hysteretic loss in superconductors for power applications, interests in future high field accelerators beyond the Large Hadron Collider (LHC) have brought new impetus and prospects.…”

Superconducting Materials and Conductors: Fabrication and Limiting Parameters

“…A major obstacle to the application of YBCO in HEP magnets is that it is difficult to form a transposed cable that enables currents in the tens-of-kA region. Roebel-type cables are considered [133][134][135], but are still in their relative infancy. Recent tests at CERN on two Roebel cables made by Karlsruhe Institute of Technology (KIT) and General Cable Superconductors (GCS), assembled from 10 and 15 12-mm-wide tapes respectively, showed critical current at 4.2 K in excess of 10 kA in a parallel 10 T background field, and approximately 4 kA in a 10 T perpendicular field [136].…”