Relation of Shunting Current at Cracked Part to Critical Current and &lt;i&gt;n&lt;/i&gt;-Value in Multifilamentary Bi2223 Composite Tape

Ochiai, Shojiro; Okuda, Hiroshi; Sugano, M.; Osamura, Kōzō; Otto, A.; Malozemoff, A. P.

doi:10.2320/matertrans.maw201201

Cited by 7 publications

(38 citation statements)

References 10 publications

(28 reference statements)

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“…It has been shown that the experimental results of coated-and filamentaryconductors are described well by this replacement. 5,6,14) Based on this finding, we use the single equivalent crack model for analysis also in this work.…”

Section: Measured Critical Currents (I C ) and N-valuesmentioning

confidence: 99%

“…(1) and (2), we can obtain the values of ð1 À fÞðL=sÞ 1=n 0 and R t by curve fitting to the measured VI curve, and, once they are estimated, the SmBCO ligament part-transported current I Sm and shunting current I s can be obtained, as has been shown in our preceding work. 5,6,14) In calculation with eqs. (1) and (2), the values of I c and n at · T = 497 MPa just below the onset stress of cracking were used as I c0 and n 0 (I c0 = 180, 171 and 183 A, and n 0 = 35.2, 36.1 and 32.2 for S1, S2 and S3, respectively).…”

Section: Model For Analysismentioning

confidence: 99%

“…Here, we denote the crack width as s, critical current in non-cracked state as I c0 , and n-value in noncracked state as n 0 . The VI relation of cracked section (L = 1.5 cm) is expressed as 5,6,14) V…”

Section: Model For Analysismentioning

confidence: 99%

“…Usually, damage takes place non-uniformly within a sample. 14) As the electric circuit of a sample is composed of series circuits of sections, the superconducting property of the sample varies, depending on the extent of damage in the sections. For safe and reliable design, it is required to describe the relation of extent of damage to superconducting property in sections and the relation of superconducting property of sections to that of overall sample.…”

Section: Introductionmentioning

confidence: 99%

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Relation of n-Value to Critical Current for Local Sections and Overall Sample in a SmBCO Coated Conductor Pulled in Tension

et al. 2014

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Under application of tensile stress to a SmBCO (SmBa 2 Cu 3 O 7¹¤ ) coated conductor sample consisting of series electric circuit of local sections, the relation of voltagecurrent curve, critical current and n-value of the sections to those of overall sample was studied. The change in critical current and n-value with increasing applied stress was different from section to section due to the difference in damage behavior of the SmBCO layer among the sections. When the difference in extent of damage among the sections was small, the voltages developed in all sections contributed to the voltage of overall sample. In this case, the critical current and n-value of overall sample were within the range of the highest and lowest values among the sections. On the other hand, when the damage in one section was far severer than that of other sections, the voltage developed in the most severely damaged section largely contributed to the overall voltage, and hence the voltagecurrent curves of the most severely damaged section were almost the same as those of overall sample. In this case, critical current of the overall sample was slightly higher and n-value of the overall sample was lower than the critical current and n-value of the most severely damaged section. Accordingly, the decrease in n-value with decreasing critical current in overall sample was sharper than that in sections. This phenomenon was accounted for by the increase in shunting current at cracked part at higher voltage in the most severely damaged section.

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Section: Measured Critical Currents (I C ) and N-valuesmentioning

confidence: 99%

Section: Model For Analysismentioning

confidence: 99%

Section: Model For Analysismentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Relation of n-Value to Critical Current for Local Sections and Overall Sample in a SmBCO Coated Conductor Pulled in Tension

et al. 2014

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“…We use the model reported by Fang et al, 12) which treats crack-induced changes in V-I curves. We have used this model to analyze the V-I curve and estimate the I c and n-value in cracked DyBCO-and SmBCO-coated conductors, 4,5,811) and in Bi 2 Sr 2 Ca 2 Cu 3 O 10+x (BSCCO) filamentary conductors 22) containing collective cracks that are composed of successively fractured filaments in a transverse cross-section. 18,22) We showed that the experimentally measured V-I curves, I c , and n-value are described by this model.…”

Section: Introductionmentioning

confidence: 99%

Effects of Heterogeneous Cracking of Superconducting Layer on Voltage-Current Curve, Critical Current, and n-Value in High-Temperature Superconducting Layer-Coated Conductor Tape

et al. 2015

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When high-temperature superconducting layer-coated conductors are exposed to high electromagnetic and/or mechanical stress and strain, the superconducting layer is damaged mainly by cracking. As cracking occurs heterogeneously, the critical current and n-value of a test specimen, which is composed of a series circuit of local sections, are dependent on the extent of cracking in local sections. In this work, the correlations of the extent of cracking in local sections with the critical current and n-value of the specimen were studied by modeling analysis. When one section is cracked, the critical current and n-value of the specimen decrease with increasing crack size. When multiple sections are cracked, the properties depend on the difference in crack size among the sections. When the crack size of the sections is similar, the critical current of the specimen decreases and the n-value increases as the number of cracked sections increases. This is caused by the increased voltage and the decreased shunting current at cracks. When there are large differences in the crack sizes of the sections, the section with the largest crack controls the voltage-current behavior of the specimen and determines the reduction in the critical current and n-value. For a given size of the largest crack, the critical current of the specimen is slightly higher and the n-value is lower when there is an intermediate difference in crack size among the sections than when there is a small difference in crack size, and the critical current is lower and the n-value is higher when there is an intermediate difference in crack size than when there is a large difference in crack size.

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Tape Length-Dependence of Critical Current and n-Value in Coated Conductor with a Local Crack

2014

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Tape length-dependence of voltagecurrent curve, critical current and n-value in a coated conductor with a local crack were studied by modeling analysis. In calculation, the specimen length was varied in the range of 1.5 to 18 cm where the influence of cracking of superconducting layer is sharply reflected in the voltagecurrent curve. The following results were obtained, which can be utilized for analysis and interpretation of the experimental results under applied tensile stress in laboratory scale of specimen length. The existence of a crack changed the critical current and n-value through the decrease in current-transportable cross-sectional area of the superconducting layer and the current shunting in the cracked cross-section for any specimen length and any crack size, while the extent of the change was dependent on specimen length and crack size. When the crack was large, critical current increased slightly and n-value decreased significantly with increasing specimen length due to the enhanced shunting current. On the other hand, when the crack was small, critical current increased slightly with specimen length due to the enhanced shunting current similarly to the case of large crack, but n-value decreased with increasing specimen length due to the enhanced shunting current but then it increased due to the enhanced voltage-development at higher voltage in the non-cracked part. Also, the features of the dependence of the relation of n-value to critical current on specimen length were revealed; the decrease in n-value with decreasing critical current became sharper for longer specimen.

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Relation of Shunting Current at Cracked Part to Critical Current and <i>n</i>-Value in Multifilamentary Bi2223 Composite Tape

Cited by 7 publications

References 10 publications

Relation of <i>n</i>-Value to Critical Current for Local Sections and Overall Sample in a SmBCO Coated Conductor Pulled in Tension

Relation of <i>n</i>-Value to Critical Current for Local Sections and Overall Sample in a SmBCO Coated Conductor Pulled in Tension

Effects of Heterogeneous Cracking of Superconducting Layer on Voltage-Current Curve, Critical Current, and <i>n</i>-Value in High-Temperature Superconducting Layer-Coated Conductor Tape

Tape Length-Dependence of Critical Current and <i>n</i>-Value in Coated Conductor with a Local Crack

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