Current-voltage characteristics of an HTS coil having a hot spot

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 volt...

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Bibliographic Details
Published in:IEEE transactions on applied superconductivity 2002-03, Vol.12 (1), p.1438-1441
Main Authors: Korpela, A., Kalliohaka, T., Lehtonen, J., Mikkonen, R., Pitel, J., Kovak, P.
Format: Article
Language:English
Subjects:
Anisotropic magnetoresistance
Applied sciences
Coiling
Coils
Critical current
CURRENT DENSITY
Current-voltage characteristics
Density
Electric fields
Electrical engineering. Electrical power engineering
Electromagnets
Exact sciences and technology
High temperature superconductors
Hot spots
Magnetic field measurement
MAGNETS
Nonuniform electric fields
Power dissipation
Silver
SUPERCONDUCTIVITY
SUPERCONDUCTORS
Various equipment and components
VOLTAGE
Voltage measurement
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Summary: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.
ISSN:1051-8223
1558-2515
DOI:10.1109/TASC.2002.1018673