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

Volume

12

Issue

1

fYear

2002

fDate

3/1/2002 12:00:00 AM

Firstpage

1438

Lastpage

1441

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;

fLanguage

English

Journal_Title

Applied Superconductivity, IEEE Transactions on

Publisher

ieee

ISSN

1051-8223

Type

jour

DOI

10.1109/TASC.2002.1018673

Filename

1018673