Study of Critical Current and n-Values of 2G HTS Tapes: Their Magnetic Field-Angular Dependence

Zhang, X.; Zhong, Zhaoyang; Geng, Jianzhao; Shen, Boyang; Ma, Jun; Li, C.; Zhang, H.; Dong, Qihuan; Coombs, Tim

doi:10.1007/s10948-018-4678-8

Cited by 43 publications

(28 citation statements)

References 16 publications

(21 reference statements)

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“…Moreover, multiple publications have already reported that the electrical properties of the large majority of 2G-HTS tapes can be strongly influenced by the intensity and direction of externally and self-induced applied magnetic fields [20,21,22], although no strong agreement has been reached in terms of the material law that governs their critical current density properties, as widely different material laws can render similar results depending on the physical quantity being studied [22,23,24]. In this sense, the simulation of the electromagnetic behaviour of 2G-HTS coils presents serious challenges, especially in conditions where one needs to consider the in-field dependence of the critical current, Ic, this in terms of the direction and intensity of the magnetic field per coil-turn, as pointed out in early experiments measuring the magnetic field distribution and AC loss of HTS thin films in superconducting coils [25,26].…”

Section: Introductionmentioning

confidence: 99%

How to Choose the Superconducting Material Law for the Modelling of 2G-HTS Coils

Robert

Fareed

2019

Materials

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In an attempt to unveil the impact of the material law selection on the numerical modelling and analysis of the electromagnetic properties of superconducting coils, in this paper we compare the four most common approaches to the E-J power laws that serve as a modelling tool for the conductivity properties of the second generation of high-temperature superconducting (2G-HTS) tapes. The material laws considered are: (i) the celebrated E-J critical-state like-model, with constant critical current density and no dependence with the magnetic field; (ii) the classical Kim’s model which introduces an isotropic dependence with the environment magnetic field; (iii) a semi-empirical Kim-like model with an orthonormal field dependence, J c ( B ) , widely used for the modelling of HTS thin films; and (iv) the experimentally measured E–J material law for SuperPower Inc. 2G-HTS tapes, which account for the magneto-angular anisotropy of the in-field critical current density J c ( B ; θ ) , with a derived function similar to Kim’s model but taking into account some microstructural parameters, such as the electron mass anisotropy ratio ( γ ) of the superconducting layer. Particular attention has been given to those physical quantities which within a macroscopic approach can be measured by well-established experimental setups, such as the measurement of the critical current density for each of the turns of the superconducting coil, the resulting distribution of magnetic field, and the curve of hysteretic losses for different amplitudes of an applied alternating transport current at self-field conditions. We demonstrate that although all these superconducting material laws are equally valid from a purely qualitative perspective, the critical state-like model is incapable of predicting the local variation of the critical current density across each of the turns of the superconducting coil, or its non-homogeneous distribution along the width of the superconducting tape. However, depending on the physical quantity of interest and the error tolerance allowed between the numerical predictions and the experimental measurements, in this paper decision criteria are established for different regimes of the applied current, where the suitability of one or another model could be ensured, regardless of whether the actual magneto angular anisotropy properties of the superconducting tape are known.

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Section: Introductionmentioning

confidence: 99%

How to Choose the Superconducting Material Law for the Modelling of 2G-HTS Coils

Robert

Fareed

2019

Materials

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“…Calculation of critical current J c is based on the experimental data obtained by Zhang et al 34 . The dependence of the critical current on the orientation and strength of magnetic ux B is performed according to a procedure described by Zhang et al 35 and described with formula…”

Section: A Modelmentioning

confidence: 99%

Improvement of the homogeneity of magnetic field by the attenuation of a selected component with an open superconducting shield made of commercial tapes

Kulikov

Kozlowski

Drobin

2019

Journal of Applied Physics

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Homogeneous magnetic fields are needed in many applications. The resolution of medical imaging techniques depends on the quality of the magnetic field, as does the efficiency of electron cooling systems used at particle accelerators. Current methods of improving homogeneity require complex arrangements of magnet windings. In this work, the application of commercial superconducting tapes for this purpose is analyzed experimentally and numerically. The shielding effect exhibited by the superconductors can be used to control the shape of the magnetic field. An open magnetic shield made of superconducting tapes is able to nullify the radial component of a solenoidal magnetic field, forming the long region of the homogeneous magnetic field. To form a shield, the superconducting tapes are wound on a former. Then, it is positioned coaxially inside an electromagnet. The measurements are performed in the DC magnetic field and at zero-field cooling conditions. A numerical model is developed to further analyze the magnetic field. New simplifications and proper constraints allow the use of an axial symmetry despite relatively complex geometry of the shields. Results from the simplified model and obtained experimentally are consistent. The decrease of radial component of the magnetic field and the significant improvement of its homogeneity are observed in a shielded region. The decrease of shielding quality with the increase of an applied magnetic field is observed. Empirical formulas describing the dependence of shielding quality on the geometry and the critical current of the shield are developed.

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“…J c is critical current. n is taken as 31 and E 0 is assumed as 100 μV • m −1 [28,29]. J z is found using 3.…”

Section: Numericalmentioning

confidence: 99%

“…Anisotropy of analysed tapes is considered based on [29]. Parameters J c0 and B 0 are fitted with data from [30] for SCS6050 tape.…”

Section: Numericalmentioning

confidence: 99%

Distribution of Trapped Magnetic Flux in Superconducting Stacks Magnetised by Angled Field

Smara

Climente-Alarcón

Glowacki

2019

J Supercond Nov Magn

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Some novel energy applications require the use of complex shapes of stacks of superconducting tapes as trapped-flux magnets. A trapped-flux magnet magnetised in a superconducting motor may experience an angled magnetising field rather than a field normal to its surface. This will affect the trapped magnetic flux distribution. This work presents the results of the numerical and experimental analyses of the stacks magnetised in an angled magnetic field. The finite element model using H-formulation is developed to compute the induced superconducting currents. The measurements are performed on stacks with different thicknesses and with different orientations against a magnetising field. The resulting distribution of the magnetic flux as well as the electric currents is computed, presented and discussed in details. The importance of the observed distribution patterns is assessed in the context of the implementation of such stacks in a fully superconducting electric motor.

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Study of Critical Current and n-Values of 2G HTS Tapes: Their Magnetic Field-Angular Dependence

Cited by 43 publications

References 16 publications

How to Choose the Superconducting Material Law for the Modelling of 2G-HTS Coils

How to Choose the Superconducting Material Law for the Modelling of 2G-HTS Coils

Improvement of the homogeneity of magnetic field by the attenuation of a selected component with an open superconducting shield made of commercial tapes

Distribution of Trapped Magnetic Flux in Superconducting Stacks Magnetised by Angled Field

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