AC losses in HTS bulk at various temperatures

• Published in: IEEE transactions on applied superconductivity 2005-06, Vol.15 (2), p.2879-2882
• Main Authors: Yamagishi, K., Asaba, I., Sekizawa, S., Tsukamoto, O., Ogawa, J., Kikukawa, K., Hirakawa, M.
• Format: Article
• Language: English
• Subjects: AC loss; Alternating current; Amplitude estimation; Applied sciences; Bulk density; Critical current density; cryo-cooler; Decay; Electric machines; Electrical engineering. Electrical power engineering; Electrical machines; Exact sciences and technology; Frequency estimation; Frequency measurement; High temperature superconductors; HTS bulk; Loss measurement; Magnetic field measurement; Magnetic fields; Miscellaneous; Perturbation methods; Studies; Superconductivity; Temperature; Temperature dependence; trap magnetic field; Trapped magnetic fields
• ISSN: 1051-8223; 1558-2515
• DOI: 10.1109/TASC.2005.848253

HTS bulks applied to electric machines are exposed to AC magnetic field perturbations which cause AC losses in the bulks. AC losses affect the efficiency of the machines and decay the trapped magnetic field in an HTS bulk. Critical current density and the maximum trapped magnetic field of a bulk are enhanced as temperature is decreased. Thereby, the lower temperature operation of the bulk is preferable. The AC losses in the bulk and their influence on the trapped magnetic field are dependent on the temperature. Therefore, to estimate the efficiency and decay of the trapped magnetic field at various operation temperatures, it is necessary to know the temperature dependence of the AC losses. We investigated AC loss characteristics of a bulk at various temperatures. In the work, AC losses were measured for the amplitude of the AC external magnetic field up to 0.08 T and frequency 17.3 Hz/spl sim/62.2 Hz at the temperature 65 K/spl sim/100 K. It is also shown that the temperature dependences of the AC losses are well estimated by a theoretical model based on the Bean model.