Transport AC Losses in Multiple-Layer Roebel Tapes

The Roebel tape is a novel high-temperature superconducting (HTS) wire with a multiple superconducting layer structure. Adjacent layers are patterned into meander-shaped multifilaments in opposite directions so that the magnetic fields generated by each layer can be mutually cancelled. The Roebel tape can be regarded as an HTS Roebel cable encapsulated into a tape, and hence has exclusive advantages such as high engineering current density, small critical current degradation, low AC losses, and a simple manufacturing process. This paper focuses on the transport AC losses of the Roebel tape with a multiple-layer structure. 3-D finite element method (FEM) models for the Roebel tapes are built based on the T-A formulation. Current distribution and AC losses of the Roebel tapes with up to 10 ReBCO layers are obtained. The results show that the tapes with even numbers of layers generate lower losses than those with odd numbers, which indicates the superconducting layers should always appear in pairs. Increasing layers can increase the engineering current density of the tape, but the average loss per layer also rises. Therefore, we suggest increasing the distance between the layer pairs or using double-layer Roebel tape stacks instead. The results indicate that the multilayer Roebel tapes can be a promising cable solution for industry and fusion applications because of the high current density and low AC losses.