Influence of Cracks in the Superconductor Layers Caused by Mechanical Stresses on Critical Currents and AC Transport Losses in YBCO CCs

Isozaki, K.; Noda, T.; Iwasaki, S.; Honzawa, R.; Ojima, Tomonori; Takao, T.; Iida, Yuya; Ogino, T.; Tsukamoto, O.

doi:10.1109/tasc.2012.2235496

Cited by 11 publications

(5 citation statements)

References 6 publications

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“…Magnetic field profile is calculated in advance by finite element analysis based on the test coil configuration and is used to determine the critical current I c [i] at i-th section. Time evolutions of voltage across the restive zone and wire temperature are calculated by (2), assuming that I t (t) changes according to (1) when a resistive zone appears where I t exceeding I c and voltage across the resistive zone exceeds a certain value of V res at t = t q . Fig.…”

Section: B Analytical Resultsmentioning

confidence: 99%

“…The authors investigate quench protection characteristics of coils wound of Bi/Ag-sheathed wires. It is considered that there are three kinds of causes of unexpected quenches during operation of HTS coils, a) local transient heat disturbances, b) appearance of non-recoverable local defects in the conductor which may be caused by fatigue effect due to repeated mechanical stresses [2] and c) appearance of long resistive zone caused by temperature rise of long part of the conductor due to malfunction of cryogenic system, for example [3], [4]. Quenches by the cause a) are rare in HTS coils because of high temperature margin of HTS wires.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Quench Protection Characteristics of Coil Wound of Bi/Ag-Sheathed Wire

Tsukamoto¹,

Fujimoto

Yamaguchi³

et al. 2015

IEEE Trans. Appl. Supercond.

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The most probable cause of quenches of a coil wound of Bi/Ag-sheathed wires is the appearance of a long resistive zone caused by the temperature rise of the long part of the conductor due to, for example, ac losses and the malfunction of the cryogenic system. Protection characteristics of quenches by this cause are experimentally and analytically investigated. In the experiment, the operating temperature of a coil wound of a Bi/Ag-sheathed wire is gradually increased until the resistive voltage of the coil exceeds a given threshold to start a quench dump sequence. Damages in the test coils are examined by changing the decay time constant of the coil current. Based on those results, conditions to protect coils from damages are investigated. Analysis is conducted to simulate quench events, and conditions for quench protection are obtained. The analytical results well explain the quench behaviors of the test coils.Index Terms-Coil wound of Bi/Ag-sheathed wire, quench experiment, quench origins, quench protection.

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Section: B Analytical Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Quench Protection Characteristics of Coil Wound of Bi/Ag-Sheathed Wire

Tsukamoto¹,

Fujimoto

Yamaguchi³

et al. 2015

IEEE Trans. Appl. Supercond.

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“…Most probable defects that newly appear during operation are caused by repeated stresses to CCs. From a result of SEM observation of CCs subjected to repeated stress it is estimated that L d does not exceed 0.1 mm [14]. Therefore, originally existing defects are major ones to consider about.…”

Section: Discussionmentioning

confidence: 99%

Study on stabilization and quench protection of coils wound of HTS coated conductors considering quench origins – Proposal of criteria for stabilization and quench protection

2014

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a b s t r a c tIt has been considered that HTS coils are hard to be quenched because of high quench energy due to high critical temperature and high specific heat of HTS wires. Therefore, attention to quench protection was not much paid. However, HTS coils still have possibility to be quenched during operation by mainly the following two origins, (a) presence of non-recoverable local defects in the conductors and (b) temperature rise of long part of the conductor. Actually, severe quench accidents, such as burning coils, are occurring in various places as scales of HTS increased. Purposes of this paper are to study on behaviors of normal zone and hot spot temperature of wires during quench detect/energy dump sequence and to find criteria for the stability and quench protection. In the paper, criteria are proposed for stability and quench protection of HTS coils. A criterion for the stability is that a coil can be operated stably without a quench against defects in coil windings and that for quench protection is that a coil can be safely protected from damages caused by a quench due to temperature rise of long part of coil wires. The criteria are used as design rules for HTS coils.

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“…Slitting the wide REBCO tape to the width required by the application can greatly reduce the cost of conductor manufacturing. However, edge cracks were observed because of the REBCO tapes slitting process by many groups [9][10][11][12][13][14][15][16][17][18][19]. Edge cracks due to the slitting process may cause the premature degradation when subjected to the tensile loading.…”

Section: Introductionmentioning

confidence: 99%

“…Liu et al showed that REBCO tapes have higher shear strength under shear stress at the center and lower shear strength at the slitting edges [21]. Isozaki et al reported that the edge cracks grow and widen under fatigue tensile stresses [13], and draw the conclusion that influence of stress/strain on critical currents can be explained by assuming that some of edge cracks are widened and grown by the stress. Mbaruku et al inferred that cracks initiated at the conductor edge and edge cracks served as crack nucleation sites during fatigue [14].…”

Section: Introductionmentioning

confidence: 99%

Evaluation of the effect of edge cracks on critical current degradation in REBCO tapes under tensile stress

Yang¹,

Song²,

Guan³

et al. 2021

Preprint

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The slitting process used for fabrication of REBa 2 Cu 3 O x (REBCO, RE=Rare earth) tapes of required width will greatly improve production efficiency and reduce production costs. However, edge cracks induced by the slitting process of wide REBCO tapes may cause the premature degradation under a extremely high hoop (tensile) stress in high-field magnets. It is necessary to evaluate the edge cracks of REBCO tapes on the critical current (I c ) degradation. This work aims to evaluate the effect of edge cracks on the I c performance under tensile stress. I c degradation under artificial cracks was measured to validate the applicability of linear elastic fracture mechanics for the REBCO film. Linear elastic fracture mechanics was used to get the mixed stress intensity factor of multiple edge oblique cracks. A model considering edge crack properties angle β, spacing d, and length a is constructed to evaluate the critical load and critical cracks properties. When the stress intensity factor at the crack tip is less than K Ic = 2.3 MPa √ m, edge cracks remain stable and do not propagate. Two kinds of REBCO tapes fabricated by different companies are evaluated, and cracks of these tapes will not cause premature degradation. This model could be used to evaluate the operation range of REBCO tapes and improve the manufacturing process.

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Influence of Cracks in the Superconductor Layers Caused by Mechanical Stresses on Critical Currents and AC Transport Losses in YBCO CCs

Cited by 11 publications

References 6 publications

Quench Protection Characteristics of Coil Wound of Bi/Ag-Sheathed Wire

Quench Protection Characteristics of Coil Wound of Bi/Ag-Sheathed Wire

Study on stabilization and quench protection of coils wound of HTS coated conductors considering quench origins – Proposal of criteria for stabilization and quench protection

Evaluation of the effect of edge cracks on critical current degradation in REBCO tapes under tensile stress

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