85 research outputs found
Experimental study of a transformer with superconducting elements for fault current limitation and energy redistribution
Numerous proposed and developed superconducting fault current limiters and
self-limiting transformers limit successfully fault currents but do not provide
uninterrupted supplying of consumers. A design investigated in the work
combines the functions of a conventional transformer with the functions of fast
energy redistribution and fault protection. The device constitutes a
transformer containing an additional high-temperature superconducting (HTS)
coil short-circuited by a thin film HTS switching element. Fault current
limitation and redistribution of the power flow to a standby line are achieved
as a result of a fast transition of the superconducting switching element from
the superconducting into the normal state. Transient and steady-state
characteristics were experimentally investigated. A mathematical model of the
device operation was proposed, and the calculated results were found to be in
good agreement with the experimental data. The application field and basic
requirements to such devices were discussed and it was shown that the proposed
device meets these requirements.Comment: 15 pages incl. 4 figures. Submitted to "Cryogenics
Thermal state of superconducting films on wide substrates
The stationary thermal state and propagation of a normal zone in a long
superconducting film on a wide substrate are analyzed analytically. Expressions
describing voltage-current characteristics and temperature-current dependence
of the film are derived for the flux creep, flux flow and normal regions. It is
shown how the flux creep influences the conditions of the thermal stability. In
particular, it is found that the bistability of the thermal state can appear in
this regime. Under the boiling crisis, the temperature-current dependence for a
film differs markedly from that for a wire and is characterized by a smooth
temperature increase with the current. A "mixed" regime is analyzed where the
flux flow and normal states exist simultaneously with the boundary between them
parallel to the film axis. Expressions for the propagation velocity of a normal
zone along a narrow film are obtained which show that this velocity in films is
sufficiently higher than in wires.Comment: 17 pages, 10 figures, submitted to "Cryogenics
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