Heating due to AC losses in high-temperature superconductors

Because of low thermal conductivity of high-temperature superconducting mat erials, AC losses can lead to pronounced heating of the interior parts of a bulk sample. For samples cooled from their surface, it results in the stro ng nonuniform distribution of temperature over the thickness. The influence of this phenomenon on the AC loss value is analyzed using the approach bas ed on the Bean critical state model complemented by the temperature depende nce of the critical current density and by the heat equation. It is shown a nalytically and by numerical calculations that the heating increases the lo sses in the magnetic fields below the complete penetration field and reduce s in fields above the complete penetration field. When the losses are calcu lated without considering the heating, the error in the loss value can achi eve a few hundreds percents, even in relatively low magnetic fields of indu strial frequency. (C) 1998 Elsevier Science B.V. All rights reserved.