Relation between different critical current criteria and quench current in HTS magnets
In practice, the critical current of an HTS magnet is the current at which a thermal runaway (quench) occurs. The stability analysis required to determine the quench current, I q is often a time consuming numerical problem. Usually the short sample critical current, I c is measured by using some ele...
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Published in | Physica. C, Superconductivity Vol. 372; pp. 1360 - 1363 |
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Main Authors | , , , , , |
Format | Journal Article |
Language | English |
Published |
Elsevier B.V
01.08.2002
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Subjects | |
Online Access | Get full text |
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Summary: | In practice, the critical current of an HTS magnet is the current at which a thermal runaway (quench) occurs. The stability analysis required to determine the quench current,
I
q is often a time consuming numerical problem. Usually the short sample critical current,
I
c is measured by using some electric field criterion. In trained LTS magnets
I
q can be estimated from
I
c due to a steep electric field (
E)–current density (
J) characteristic. For HTS magnets the situation is more complicated due to the anisotropy and slanted
E(
J)-characteristics. In this paper the theoretical maximum of
I
q,
I
q
max
of conduction cooled HTS magnets is computationally compared with different critical current criteria at 20 K. Computations are based on the
I
c data measured with a Bi-2223/Ag tape. Two electric field criteria, 1 and 0.1 μV/cm, are applied to the magnets by investigating both the maximum electric field in a single turn of the coil and the voltage between the magnet poles. The critical currents obtained by these criteria are compared with
I
q
max
in several coil geometries of a solenoidal conduction cooled HTS magnet having the wire length of 2, 5 and 10 km.
I
q
max
is determined from the balance between the available cooling power and the total loss power generated inside the magnet. The objective is to enable a magnet designer to determine a safe operation current for an HTS magnet without performing a detailed stability analysis. |
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Bibliography: | ObjectType-Article-2 SourceType-Scholarly Journals-1 ObjectType-Feature-1 content type line 23 |
ISSN: | 0921-4534 1873-2143 |
DOI: | 10.1016/S0921-4534(02)01029-8 |