Degradation-Free Impregnated YBCO Pancake Coils by Decreasing Radial Stress in the Windings and Method for Evaluating Delamination Strength of YBCO-Coated Conductors

Miyazaki, Hiroshi; Iwai, Sadanori; Tosaka, Taizo; Tasaki, Kenji; Ishii, Yusuke

doi:10.1109/tasc.2013.2287054

Cited by 55 publications

(19 citation statements)

References 18 publications

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“…However, the 3-D model of the experimental setup leads to large numbers Table I summarizes the mechanical properties and thickness of the constituent materials of the YBCO CC [16], [17]. Fig.…”

Section: A Stress Distribution Of Ybco Tapes Under Shear Stressmentioning

confidence: 99%

Delamination Properties of YBCO Tapes Under Shear Stress Along the Width Direction

Liu

Zhu

Yang

et al. 2016

IEEE Trans. Appl. Supercond.

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In YBCO coils, the increased transport current density and magnetic field will induce larger electromagnetic force, and YBCO coated conductors (CCs) may suffer interlayer delamination by shear forces, which may give rise to performance degradation of the conductor. The delamination characteristics of YBCO CCs under shear stress should be well understood for better application of YBCO tapes to high-temperature superconducting equipment. This paper describes the experimental results for different delamination strength and critical current I c degradation behaviors of the YBCO CCs under shear stress at the unslit edge, center, and slit edge of the conductor. The results show that the average delaminated shear strengths of 4.9, 5.9, and 3.7 MPa are recorded for the unslit edge, center, and slit edge at room temperature, whereas 6.8, 7.2, and 5.1 MPa are recorded for the unslit edge, center, and slit edge at liquid nitrogen. The different degradation behaviors of I c under shear stress are related to the location where delamination occurs in the sample. According to the finite-element method analysis for the stress distribution of the conductor under shear stress, stress concentration leads to initial delamination of the conductor. The decrease of moment arm is suggested to reduce the effect of moment on the delamination test.

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Section: A Stress Distribution Of Ybco Tapes Under Shear Stressmentioning

confidence: 99%

Delamination Properties of YBCO Tapes Under Shear Stress Along the Width Direction

Liu

Zhu

Yang

et al. 2016

IEEE Trans. Appl. Supercond.

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“…This indicates that besides material processing, some other reason, such as the epoxy impregnation, causes the lower critical current of the coil. In [2], [14], it is reported that mechanical stress can cause a decreased n-value and critical current in an impregnated coil due to the difference in thermal contraction of the materials in the coil, such as the coil former, conductor constituents, impregnation resin, bandages and heat-sink materials. Therefore, the impregnation could be considered the most important reason for the decreasing of n-value and critical current of the coil in this case.…”

Section: Resultsmentioning

confidence: 99%

“…However, few papers investigate the variation in its properties along the length of the tape using detailed DC characterization of the HTS coil. It is a common phenomenon that some non-uniformity exists along the length of an HTS coated conductor [2], [4], [5], [7], [10]- [14]. This variation may be for several reasons, such as an uneven manufacturing process or damage from cutting, handling or winding.…”

Section: Introductionmentioning

confidence: 99%

DC characterization and 3D modelling of a triangular, epoxy-impregnated high temperature superconducting coil

Ainslie

Rush

et al. 2015

Supercond. Sci. Technol.

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Abstract-Direct current (DC) characterization of high temperature superconducting (HTS) coils is important for HTS applications, such as electric machines, superconducting magnetic energy storage (SMES) and transformers. In this paper, DC characterization of a circular, epoxy-impregnated HTS coil made from YBCO coated conductor for use as a prototype axial flux HTS electric machine is presented. Multiple voltage taps were utilized within the coil during measurement to help provide further detailed information on its DC behavior as a function of length. Based on the experimental results, there exist regions of non-uniformity along the length of superconductor in the coil, resulting in non-ideal superconducting properties of the coil. By studying the current-voltage (I-V) curves across different regions, it is found that a decreasing n-value and critical current exists in the non-uniform parts of the HTS coil. 

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“…Despite the different adopted fabrication techniques that have been used, these CCs have multilayered structures because of the intrinsic brittle nature of superconducting ceramic, which makes it possible to subject the CCs to some deformation while carrying high currents. However, in practical utilization, thermal stress [5,6] and Lorentz forces [4,7], as major stress sources exerted on CCs in the transverse direction lead to critical current (I c ) degradation, these have been found in either epoxy impregnated coils during cooling [8] or paraffin impregnated coils after charging in a strong back magnetic field [9]. Results indicate that the layers between the Ag layer and the substrate layer delaminate and break, which then cause I c degradation.…”

Section: Introductionmentioning

confidence: 99%

A standardized measurement method and data analysis for the delamination strengths of YBCO coated conductors

Zhang

Sun

Liu

et al. 2020

Supercond. Sci. Technol.

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Of crucial importance for the application of high temperature superconducting coated conductors (CCs) is the delamination strength due to thermal stress and Lorentz force during their operation. This paper reports the mechanical delamination strengths of YBCO CCs at room temperature and 77 K, as well as the electro-mechanical delamination strength form a modified anvil tensile method. Compared to previous measurement setups, our anvil device only has one degree of freedom of transverse tension. Moreover, we use a vertical soldering technique to ensure the data reliability. Since we eliminate the influence of the measurement method on the experimental results, a naturally discrete property of the delamination strength is obtained. To describe these experimental data, a three-parameter Weibull distribution function has been suggested and a new criterion for determining delamination strength is proposed from the reliability function, which can be conveniently referred to for engineering design.

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Degradation-Free Impregnated YBCO Pancake Coils by Decreasing Radial Stress in the Windings and Method for Evaluating Delamination Strength of YBCO-Coated Conductors

Cited by 55 publications

References 18 publications

Delamination Properties of YBCO Tapes Under Shear Stress Along the Width Direction

Delamination Properties of YBCO Tapes Under Shear Stress Along the Width Direction

DC characterization and 3D modelling of a triangular, epoxy-impregnated high temperature superconducting coil

A standardized measurement method and data analysis for the delamination strengths of YBCO coated conductors

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