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Dynamics of the Josephson Multi-Junction Systems with Junctions Characterized by Non-Sinusoidal Current - Phase Relationship

100%
Abal'osheva I., Lewandowski S.
Acta Physica Polonica A
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2004
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vol. 106
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issue 5
687-691
EN
It is shown that the inclusion of junctions characterized by non-sinusoidal current - phase relationship in the systems composed of multiple Josephson junctions - results in the appearance of additional system phase states. Numerical simulations and stability considerations confirm that these phase states can be realized in practice. Moreover, spontaneous formation of the grain boundary junctions in high-T_c superconductors with non-trivial current-phase relations due to the d-wave symmetry of the order parameter is probable. Switching between the phase states of multiple grain boundary junction systems can lead to additional 1/f noise in high-T_c superconductors.
2
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Applicable Damage of High-T_{ rm c} YbaCuO Superconducting Tapes by Current and Laser Pulses

100%
Kiprijanovič O., Ašmontas S., Anisimovas F., Gradauskas J.
Acta Physica Polonica A
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2011
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vol. 119
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issue 2
256-258
EN
Damage and irreversible damage of YBaCuO tapes with high density current after switching from superconducting to normal state are investigated. Quasi-homogeneous current distribution across the tape in superconducting state can cause perfect tape damage or irreversible damage when current is slightly above critical value. The model of the tape heating during the optically initiated switching from superconducting to normal state is proposed. Analysis of causes inducing damage shows necessity to consider 0.5T_{m} damage criterion because of strong current influence on the damage processes. Possible damage mechanisms are described and crack tips motion simultaneously with switching from superconducting to normal state is considered. Application of optically illuminated YBaCuO tapes with nanosecond duration current pulses on the base of the described mechanisms is proposed.
3
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Higher harmonics in the voltage on a superconducting wire carrying AC electrical current

88%
Tebano R., Gömöry F.
Open Physics
|
2003
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vol. 1
|
issue 2
246-257
EN
The problem of determining the harmonic content in the voltage that appears on a superconducting wire carrying cosine-like AC current was resolved theoretically, using two approaches. First, the Fourier components of the voltage spectrum were found by numerical integration. Importance of individual terms was established, leading to two conclusions: a) it is the cosine component of the 3rd harmonic that represents the bulk of harmonic distortion, b) for the practical purposes it is sufficient to consider higher harmonics with n ≤ 7. Then, the analytical formulas were derived. While for the sine components a general expression containing an infinite series was found, closed-form formulas were derived for the cosine components of the harmonics 1, 3, 5, 7. Consequences of the results to the experimental technique used to study the AC transport properties of superconductors are discussed.
4
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Fault Current Limitation by 2G HTS Superconducting Transformer - Experimental Investigation

75%
Wojtasiewicz G.
Acta Physica Polonica A
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2016
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vol. 130
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issue 2
516-520
EN
Transformers represent one of the oldest and most mature elements in a power transmission and distribution network. The new superconducting transformers are smaller and lighter than conventional ones and they have lower power losses, too. Also, the new 2G superconducting tapes with high resistivity in the normal state allow to build transformers with high short-circuit strength. The short-circuit current limiting feature of the superconducting transformer, which is the most important benefit of replacing conventional windings by superconducting ones, provides protection and significantly reduces the wear and tear of circuit breakers and other substation power equipment. This paper describes the design and experimental investigations results of a model of a 1-phase, 8.8 kVA superconducting transformer with windings made of 2G HTS tape. A special regard is given to the ability of the device's superconducting winding to limit the short-circuit current, in particular its equivalent resistance in normal state at a temperature of 77 K (i.e. resistance of the resistive layers of the HTS tape just after transition to the non-superconducting state).
5
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Superconducting Devices for Power Engineering

63%
Janowski T., Kondratowicz-Kucewicz B., Wojtasiewicz G., Kozak S., Kozak J., Majka M., Jaroszyński L.
Acta Physica Polonica A
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2016
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vol. 130
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issue 2
537-544
EN
The paper presents the current state of research on superconducting devices for the electrical power system, i.e. transformers, fault-current limiters, and energy storages. In particular, it describes scientific achievements of the Laboratory of Superconducting Technologies of Electrotechnical Institute. The development of distributed and renewable energy sources, as well as the increasing number of receivers with low power factor will rise interest in superconducting fault-current limiters and superconducting transformers rated below 1 MVA. Previous studies were focused on the largest power transformers and highest current superconducting fault-current limiters. ReBCO coated conductors allow to build efficient superconducting AC devices. Superconducting tape of a layered structure (second generation HTS tape) enables the construction of transformer rated up to a few MVA without the usage of parallel conductors. Relatively high resistance of the tape in normal state allows to build fault-current limiters and fault-current limiting transformers. Superconducting transformers and superconducting fault-current limiters can help to increase connected power of distribution stations and thereby accelerate development of renewable energy sources.
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