Frequency dependence of magnetic ac loss in a Roebel cable made of YBCO on a Ni–W substrate

• Published in: Superconductor science & technology 2010-08, Vol.23 (8), p.085009-085009
• Main Authors: Lakshmi, L S, Staines, M P, Badcock, R A, Long, N J, Majoros, M, Collings, E W, Sumption, M D
• Format: Article
• Language: English
• Subjects: Applied sciences; Cables; Copper; COPPER OXIDE; Electric connection. Cables. Wiring; Electrical engineering. Electrical power engineering; Exact sciences and technology; FREQUENCY; Hysteresis; Materials; MECHANICAL HYSTERESIS; Nickel; NICKEL ALLOYS (50 TO 99 NI); Nickel base alloys; Orientation; Strands; SUPERCONDUCTORS; Various equipment and components; WIRE AND CABLE; YBCO superconductors; YTTRIUM OXIDE
• ISSN: 0953-2048; 1361-6668
• DOI: 10.1088/0953-2048/23/8/085009

We have investigated the frequency dependent contributions to the magnetic ac loss in a 10 strand Roebel cable with 2 mm wide non-insulated strands and a transposition length of 90 mm. This cable is made from 40 mm wide YBCO coated conductor tape manufactured by AMSC and stabilized by electroplating 25 mu m thick copper on either side prior to the mechanical punching of the cable strands. The measurements were carried out in both perpendicular and parallel field orientation, at frequencies in the range of 30--200 Hz. While the loss in the perpendicular orientation is predominantly hysteretic in nature, we observe some frequency dependence of the loss when the cable approaches full flux penetration at high field amplitudes. The magnitude is consistent with eddy current losses in the copper stabilization layer. This supports the fact that the inter-strand coupling loss is not significant in this frequency range. In the parallel field orientation, the hysteresis loss in the Ni--W alloy substrate dominates, but we see an unusually strong frequency dependent contribution to the loss which we attribute to intra-strand current loops.