A.C. loss measurements in high-T sub(c) superconductors

• Published in: Applied superconductivity Vol. 3; no. 6; pp. 339 - 349
• Main Authors: Beghin, E, Bock, J, Duperray, G, Legat, D, Herrmann, P F
• Format: Journal Article
• Language: English
• Published: 01.01.1995
• ISSN: 0964-1807

Low a.c. loss is a key issue for electrical engineering applications of high-T sub(c) superconductors at industrial frequencies. Different material options are characterized by three different a.c. loss measurement techniques which approach as much as possible the application conditions of the conductors. Melt-textured-growth YBa sub(2)Cu sub(3)O sub(7-x) bulk samples, suitable for magnetic bearings, are characterized in an external a.c. field by magnetization measurements. Melt-casted Bi sub(2)Sr sub(2)Ca sub(2)Cu sub(3)O sub(8-x) samples and powder-in-tube Bi sub(2)Sr sub(2)Ca sub(2)Cu sub(3)O sub(10-x) tapes are suitable for current leads or power cables. In these applications the conductors are exposed to a.c. transport currents. The associated losses in self field are measured by a very sensitive electrical measurement technique. Finally, a calorimetric method is necessary when larger conductors (for instance Bi sub(2)Sr sub(2)Ca sub(2)Cu sub(3)O sub(8-x) tubes) are tested under transport currents I sub(t), generating a transverse magnetic field H proportional to I sub(t), as encountered in magnet windings for SMES, transformers or generators. The results show that the a.c. losses are sufficiently low for self field applications at industrial frequencies and a comparison of the different high T sub(c) superconductors is given. The results show further that the a.c. losses are essentially hysteretic and can be modeled using the Bean model.