Investigation of the effect of striated strands on the AC losses of 2G Roebel cables

Abstract

The assembly of meander shaped coated conductor tapes by the Roebel technique is apromising way to manufacture high current cables with low ac losses. The application oflongitudinal striations to the single strands can be an option to create a filament structurefor further possible reduction of the ac losses. Due to the complex Roebel strandgeometry, it was important to identify a reliable technique to produce such structuresusing a picosecond-infrared (IR) laser for the groove etching process. We analyzedthe effects of the filament structure on the magnetization ac loss behavior bycomparing the losses of a cable with striated strands with those of a reference one withnon-striated strands. The ac loss reduction in the Roebel cable with striated strandswas confirmed. The measured magnetization loss of the 125 mm striated singlestrand is five times lower than that of the non-striated one. In the case of thecable sample the loss reduced by a factor of three, but not in the whole intervalof amplitudes of the applied magnetic field. We also compared the results withthose for a cable with insulated striated strands: they seem to indicate that thecoupling currents occur mostly between the filaments, not between the strands.