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

Abstract

We have investigated the frequency dependent contributions to the magneticac loss in a 10 strand Roebel cable with 2 mm wide non-insulated strands anda transposition length of 90 mm. This cable is made from 40 mm wide YBCOcoated conductor tape manufactured by AMSC and stabilized by electroplating25 µm thick copper on either side prior to the mechanical punching of the cable strands. Themeasurements were carried out in both perpendicular and parallel field orientation, atfrequencies in the range of 30–200 Hz. While the loss in the perpendicular orientation ispredominantly hysteretic in nature, we observe some frequency dependence of theloss when the cable approaches full flux penetration at high field amplitudes.The magnitude is consistent with eddy current losses in the copper stabilizationlayer. This supports the fact that the inter-strand coupling loss is not significantin this frequency range. In the parallel field orientation, the hysteresis loss inthe Ni–W alloy substrate dominates, but we see an unusually strong frequencydependent contribution to the loss which we attribute to intra-strand current loops.