Journal ArticleDOI
Dynamic resistance in a slab-like superconductor with Jc(B) dependence
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TLDR
In this article, the dynamic resistance in a slab-like superconductor is calculated, taking into account a field-dependent critical current density, and the model predicts the observed dependence of dynamic resistance on field amplitude, field frequency and transport current.Abstract:
The dynamic resistance in a slab-like superconductor is calculated, taking into account a field-dependent critical current density. In superconductors carrying DC transport current in an AC external magnetic field, the dynamic resistance causes a transport loss which depends on the amplitude and frequency of this field as well as on the transport current. This resistance is calculated analytically in a critical-state model applied to a superconducting slab in a parallel field. The field has a general periodic time dependence and for the superconductor a relation between critical current and momentary magnetic field as in the Kim model is assumed. The dynamic resistance appears only at field amplitudes larger than the so-called threshold field, which depends on the transport current. The model predictions are compared with experimental results obtained with a Bi-2223/Ag tape at liquid-nitrogen temperature. At small field amplitude and at low transport current, the derived model predicts the observed dependence of dynamic resistance on field amplitude, field frequency and transport current. For a larger field amplitude and simultaneous high transport current, the resistance is found to be larger than the model predicts. This is probably due to the not completely slab-like geometry and/or to a different field dependence of the critical current density in a high AC field.read more
Citations
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Journal ArticleDOI
Computation of Losses in HTS Under the Action of Varying Magnetic Fields and Currents
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Journal ArticleDOI
Dynamic resistance of a high-Tc superconducting flux pump
TL;DR: In this article, a mechanically rotating superconducting flux pump was used to excite an HTS double pancake coil at 77 K. This flux pump is found to possess an effective internal resistance, Reff, which varies linearly with frequency, and is two orders of magnitude larger than the measured series resistance of the soldered contacts within the circuit.
Journal ArticleDOI
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Jianzhao Geng,Tim Coombs +1 more
TL;DR: In this article, the authors proposed a flux pumping mechanism for high-tc superconducting (HTS) coils with an experimental verification and an analytical model, where the basic principle is that flux flow can be triggered when the superconductor carrying a direct current is subjected to a perpendicular AC magnetic field.
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Chris W. Bumby,Rodney A. Badcock,Hae-Jin Sung,Kwangmin Kim,Zhenan Jiang,A. E. Pantoja,Patrick Bernardo,Patrick Bernardo,Minwon Park,R. G. Buckley +9 more
TL;DR: In this article, a brushless HTS-PM exciter is proposed to inject a superconducting DC current into the rotor coil circuit, which can significantly alter the thermal load upon the cryogenic system by removing the need for thermally inefficient normalconducting current leads.
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Impact of flux gap upon dynamic resistance of a rotating HTS flux pump
TL;DR: In this article, the effect of varying the size of the flux gap between the rotor magnets and coated conductor stator from 1 to 7.5 mm was investigated and it was shown that the performance of an experimental mechanically rotating HTS flux pump ceases to maintain a measurable output at flux gaps above 7.
References
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Journal ArticleDOI
Calculation of hysteresis losses in hard superconductors carrying ac: isolated conductors and edges of thin sheets
TL;DR: In this article, two methods of calculating hysteresis losses in hard superconductors are described and the London model is assumed in which the critical current density is taken independent of magnetic field.
Journal ArticleDOI
Effective resistance of current-carrying superconducting wire in oscillating magnetic fields 1: Single core composite conductor
TL;DR: In this paper, the influence of oscillating magnetic fields on the dc transport current in a single core superconducting wire has been studied by observing the terminal voltage of the wire.
Journal ArticleDOI
Alternating field losses in superconducting wires carrying dc transport currents: Part 1 single core conductors
TL;DR: In this article, the influence of dc transport currents on alternating-field hysteresis loss was investigated for a single core superconducting wire, and the results were compared with calculations based on a slab model.
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