Theoretical Analysis of Additional AC Loss Properties of Two-Strand Transposed Parallel Conductors Composed of REBCO Superconducting Tapes

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Abstract

Superconducting tapes made of REBa2Cu3Oy (REBCO; RE: rare earth, i.e., Y, Gd, or Eu) exhibit superior performance at the critical current density, even at liquid-nitrogen temperatures. However, the current capacity of these tapes must be enhanced for use in large-scale applications. We have proposed a method of constructing parallel conductors, which must be insulated and transposed to obtain uniform current sharing and low ac loss. If the transposition points deviate from the optimal ones, a shielding current is induced to maintain a constant interlinkage magnetic flux, which produces an additional ac loss. In our previous studies, the theoretical expressions for the additional ac loss were derived on the basis of a critical state model. In this study, by using an n-value model to express the I-V characteristics of REBCO superconducting tapes, we theoretically investigated the additional ac loss properties of two-strand transposed parallel conductors wound into solenoid coils. The results showed that under the nonsaturation condition, the additional ac loss increases with decreasing n value. This suggests that in parallel conductors composed of REBCO tapes that operate at liquid-nitrogen temperatures, transposition must be performed with high accuracy at the optimal points. To avoid increasing the additional ac loss, the n value of the tapes must be consistently larger than approximately 10, and the deviation of the transposition point should remain below a few percent of the conductor length.

Original languageEnglish
Article number8263126
JournalIEEE Transactions on Applied Superconductivity
Volume28
Issue number3
DOIs
Publication statusPublished - Apr 2018

Fingerprint

Superconducting tapes
strands
tapes
alternating current
conductors
Tapes
Liquid nitrogen
liquid nitrogen
Solenoids
Induced currents
Magnetic flux
solenoids
Shielding
Rare earths
shielding
magnetic flux
critical current
coils
rare earth elements
current density

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Electrical and Electronic Engineering

Cite this

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abstract = "Superconducting tapes made of REBa2Cu3Oy (REBCO; RE: rare earth, i.e., Y, Gd, or Eu) exhibit superior performance at the critical current density, even at liquid-nitrogen temperatures. However, the current capacity of these tapes must be enhanced for use in large-scale applications. We have proposed a method of constructing parallel conductors, which must be insulated and transposed to obtain uniform current sharing and low ac loss. If the transposition points deviate from the optimal ones, a shielding current is induced to maintain a constant interlinkage magnetic flux, which produces an additional ac loss. In our previous studies, the theoretical expressions for the additional ac loss were derived on the basis of a critical state model. In this study, by using an n-value model to express the I-V characteristics of REBCO superconducting tapes, we theoretically investigated the additional ac loss properties of two-strand transposed parallel conductors wound into solenoid coils. The results showed that under the nonsaturation condition, the additional ac loss increases with decreasing n value. This suggests that in parallel conductors composed of REBCO tapes that operate at liquid-nitrogen temperatures, transposition must be performed with high accuracy at the optimal points. To avoid increasing the additional ac loss, the n value of the tapes must be consistently larger than approximately 10, and the deviation of the transposition point should remain below a few percent of the conductor length.",
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AB - Superconducting tapes made of REBa2Cu3Oy (REBCO; RE: rare earth, i.e., Y, Gd, or Eu) exhibit superior performance at the critical current density, even at liquid-nitrogen temperatures. However, the current capacity of these tapes must be enhanced for use in large-scale applications. We have proposed a method of constructing parallel conductors, which must be insulated and transposed to obtain uniform current sharing and low ac loss. If the transposition points deviate from the optimal ones, a shielding current is induced to maintain a constant interlinkage magnetic flux, which produces an additional ac loss. In our previous studies, the theoretical expressions for the additional ac loss were derived on the basis of a critical state model. In this study, by using an n-value model to express the I-V characteristics of REBCO superconducting tapes, we theoretically investigated the additional ac loss properties of two-strand transposed parallel conductors wound into solenoid coils. The results showed that under the nonsaturation condition, the additional ac loss increases with decreasing n value. This suggests that in parallel conductors composed of REBCO tapes that operate at liquid-nitrogen temperatures, transposition must be performed with high accuracy at the optimal points. To avoid increasing the additional ac loss, the n value of the tapes must be consistently larger than approximately 10, and the deviation of the transposition point should remain below a few percent of the conductor length.

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