Numerical calculation of AC losses in multi-layer superconducting cables composed of coated conductors

Abstract

Two types of four-layer cables composed of coated conductors, with practical cross-sectional geometries and various critical currents, were designed. The AC losses in the cables were numerically calculated using a numerical model employing a one-dimensional FEM (1D model). The AC loss of each layer in the four-layer cable with w = 4.0 mm was compared with Norris's analytical values, Q NS , for a wide range of I t /I c . The AC loss in the first (innermost) layer was smaller than its Q NS , whereas the losses in the outer layers were close to, or much larger than, their Q NS . These results indicate that, in multi-layer cables, the AC loss in an outer layer increases because of the magnetic field generated by the current in the inner layers, and the entire AC loss of the cable is dominated by the AC losses in the outer layers. The AC losses in the four-layer cables with w = 3.3 mm, which had smaller gaps between the conductors, were smaller than those for the cable where w = 4.0 mm. These results showed the effectiveness of using narrower conductors and decreasing the gaps to reduce AC loss in multi-layer cables composed of coated conductors. The AC losses of the four-layer cable with w = 3.3 mm and I cc /w = 500 A cm −1 at 1 and 3 kArms were much smaller than the measured AC losses in cables fabricated with YBCO-coated conductors or BSCCO tapes. The AC loss in a four-layer cable with practical cross-sectional geometries should approximately be within an order of magnitude of their Q NS .

A new numerical approach to find current distribution and AC losses in coaxial assembly of twisted HTS tapes in single layer arrangement

“…This is due to the fact that when the number of tapes increases the gap between the tapes decreases and for smaller gaps each tape experiences a magnetic field which is predominantly parallel to its width, whereas the perpendicular component near its edges tends to be smaller. The same observation has been reported in previous studies [2,3]. Since the former radius is fixed, for a given number of tapes a smaller pitch length (i.e.…”

“…Several 2D methods neglecting the twisted configuration have been proposed for computing AC losses in HTS cables [1][2][3][4]. While providing useful information on the AC losses, these methods cannot be used for designing purposes, where finding the optimal twist design is an important issue.…”

Transport AC Losses in Soldered Joint of the YBCO-Coated Conductors

“…So far, there are several possible joining techniques presented in literatures [4][5][6][7][8][9][10][11][12][13][14][15], including superconducting joints, non-superconducting joints using a low melting point metal as a soldering material, and diffusion joints. Lots of researches [4][5][6][7][8][9][10][11][12][13][14][15] were focused on how to achieve very small contact resistivity and the good electro-mechanical properties of the joints, while there are few reports on the transport AC loss characteristic in the joints, which is one of the decision factors for future use of the YBCO CC in electric power applications [16][17][18][19][20][21]. In this paper, several soldered joints were fabricated, and the transport AC losses in case of self-field and 77 K were measured.…”

A Matrix Approach for the Evaluation of the Internal Impedance of Multilayered Cylindrical Structures

“…The current interest paid to multilayered structures (in connection to its fabrication, and applications concerning superconductivity, skin effect, eddy currents, and photonic metamaterial structures) is witnessed in recent publications [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]. Nonetheless, the research topic on multilayered radially inhomogeneous cylindrical structures has received scarce attention.…”