The AC loss occurred in REBa2Cu3Oy (REBCO, RE = rare earth elements, Y, Eu, Gd) superconductor is serious problem in AC applications because it may cause a severe temperature rise of superconducting systems. Therefore, it is necessary to understand the AC loss property of REBCO superconducting tape in detail and to reduce that. As AC application such as motor, the tape is mostly stacked into multi-layer. Thus, understanding the relation between the number of the stacked tapes and the AC loss is one of the most important subjects. So far, we confirmed that the AC loss of the n-layer stacked REBCO superconducting tapes decreases to 1/n of that of 1-layer for the magnitude of the applied external field, Bm, below the penetration field, Bp, and such property can be explained from the viewpoint of the demagnetizing coefficient. However, the result in that report was only at 50 K and such property was not systematically confirmed at other temperatures. In this study, the AC loss decreasing property owing to stacking tapes for Bm below Bp was investigated via experiments. Furthermore, such property was considered theoretically from the viewpoint of the demagnetizing coefficient of the stacked REBCO superconducting tapes. Consequently, it was cleared, from theoretical consideration, that the n dependence of the AC loss can be explained quantitatively by the demagnetizing coefficient, and, in order to apply the theory to the experimental results, the stacked tapes have to satisfy the restrictions which are D/w < 0.1 and t/w << 1. Here, D, w and t are the distance between the neighboring superconducting layers, the width and the thickness of the superconducting layer. Moreover, from such AC loss property, it was revealed that the n dependence of Bp can be expressed as a power function. Using the results obtained in this study, the AC losses of the stacked tapes can be estimated easily from that of 1-layer tape.
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics
- Energy Engineering and Power Technology
- Electrical and Electronic Engineering