Title :
Current-voltage characteristics of an HTS coil having a hot spot
Author :
Korpela, A. ; Kalliohaka, T. ; Lehtonen, J. ; Mikkonen, R. ; Pitel, J. ; Kovak, P.
Author_Institution :
Lab. of Electromagn., Tampere Univ. of Technol., Finland
fDate :
3/1/2002 12:00:00 AM
Abstract :
Due to a slanted electric field-current density characteristics some power dissipation exists in HTS magnets even at operation currents below a critical current determined by using some electric field criterion. Thus, the temperature inside an HTS magnet does not remain constant during a single voltage (V)-current (I) measurement. Furthermore, a sufficiently large operation current will produce a hot spot in the turn of the maximum electric field inside the coil. In this paper the effect of the temperature increase during a V (I)-measurement on the V (I)-characteristics of a Bi-2223/Ag coil is studied at 20, 40 and 56 K. The V (I)-calculations take into account both the material inhomogeneity and anisotropy and are based on the short sample data measured with the Bi-2223/Ag tape. The investigation is concentrated at overcritical currents, where the effect of temperature increase on the V (I) -characteristics of the coil is significant.
Keywords :
bismuth compounds; calcium compounds; critical currents; high-temperature superconductors; silver; strontium compounds; superconducting coils; superconducting magnets; superconducting tapes; 20 K; 40 K; 56 K; Bi-2223/Ag tape; Bi2Sr2Ca2Cu3O-Ag; HTS coil; HTS magnet; critical current; current-voltage characteristics; electric field-current density characteristics; hot spot; material anisotropy; material inhomogeneity; overcritical current; power dissipation; Anisotropic magnetoresistance; Coils; Critical current; Current-voltage characteristics; High temperature superconductors; Magnetic field measurement; Magnets; Nonuniform electric fields; Power dissipation; Voltage measurement;
Journal_Title :
Applied Superconductivity, IEEE Transactions on
DOI :
10.1109/TASC.2002.1018673
