Numerical Modeling of Dynamic Loss in HTS-Coated Conductors Under Perpendicular Magnetic Fields

© 2017 IEEE. High-Tc superconducting (HTS)-coated conductors are a promising option for the next-generation power devices. However, their thin-film geometry incurs dynamic loss when exposed to a perpendicular external ac magnetic field, which is difficult to predicate and estimate. In this paper, we propose and verify a numerical simulation model to predict the dynamic loss in HTS-thin-coated conductors by taking into account their Jc-B dependence and I-V characteristics. The model has been tested on a SuperPower YBCO-coated conductor, and we observed a linear increase of dynamic loss along the increasing field amplitude after the threshold field. Our simulation results agree closely with experimental measurements as well as an analytical model. Furthermore, the model can predict the nonlinear increase of dynamic loss at high current, while the analytical model deviates from the measurement results and still shows a linear correlation between the dynamic loss and the external magnetic field. In addition, we have used this model to simulate the distributions of magnetic field and current density when dynamic loss occurs. Results clearly show the flux traversing the coated conductor, which causes dynamic loss. These distributions have also been used to analyze the change of dynamic loss when either the transport current or the magnetic field increase individually, while the other factor remains constant. The simulation analysis on dynamic loss is done for the first time in this paper, and our results clearly demonstrate how dynamic loss changes as well as its dependence on transport current and magnetic field. © 2018 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.

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Dynamic resistance of a high-T c coated conductor wire in a perpendicular magnetic field at 77 K

10.26686/wgtn.14331536 ◽

2021 ◽

Author(s):

Zhenan Jiang ◽

R Toyomoto ◽

N Amemiya ◽

X Zhang ◽

Christopher Bumby

Keyword(s):

Magnetic Field ◽

Critical Currents ◽

Transport Current ◽

Field Amplitude ◽

Threshold Field ◽

Dynamic Resistance ◽

Coated Conductor ◽

Flux Flow ◽

Wide Range ◽

Perpendicular Field

Superconducting high-Tc coated conductor (CC) wires comprise a ceramic thin film with a large aspect ratio. This geometry can lead to significant dissipative losses when exposed to an alternating magnetic field. Here we report experimental measurements of the 'dynamic resistance' of commercially available SuperPower and Fujikura CC wires in an AC perpendicular field. The onset of dynamic resistance occurs at a threshold field amplitude, which is determined by the total DC transport current and the penetration field of the conductor. We show that the field-dependence of the normalised magnetisation loss provides an unambiguous value for this threshold field at zero transport current. From this insight we then obtain an expression for the dynamic resistance in perpendicular field. This approach implies a linear relationship between dynamic resistance and applied field amplitude, and also between threshold field and transport current and this is consistent with our experimental data. The analytical expression obtained yields values that closely agree with measurements obtained across a wide range of frequencies and transport currents, and for multiple CC wires produced by different wire manufacturers and with significantly differing dimensions and critical currents. We further show that at high transport currents, the measured DC resistance includes an additional nonlinear term which is due to flux-flow resistance incurred by the DC transport current. This occurs once the field-dependent critical current of the wire falls below the DC transport current for part of each field cycle. Our results provide an effective and simple approach to calculating the dynamic resistance of a CC wire, at current and field magnitudes consistent with those expected in superconducting machines. This is the Accepted Manuscript version of an article accepted for publication in 'Superconductor Science and Technology'. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The Version of Record is available online at https://doi.org/10.1088/1361-6668/aa54e5.

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Dynamic resistance of a high-T c coated conductor wire in a perpendicular magnetic field at 77 K

10.26686/wgtn.14331536.v1 ◽

2021 ◽

Author(s):

Zhenan Jiang ◽

R Toyomoto ◽

N Amemiya ◽

X Zhang ◽

Christopher Bumby

Keyword(s):

Magnetic Field ◽

Critical Currents ◽

Transport Current ◽

Field Amplitude ◽

Threshold Field ◽

Dynamic Resistance ◽

Coated Conductor ◽

Flux Flow ◽

Wide Range ◽

Perpendicular Field

Superconducting high-Tc coated conductor (CC) wires comprise a ceramic thin film with a large aspect ratio. This geometry can lead to significant dissipative losses when exposed to an alternating magnetic field. Here we report experimental measurements of the 'dynamic resistance' of commercially available SuperPower and Fujikura CC wires in an AC perpendicular field. The onset of dynamic resistance occurs at a threshold field amplitude, which is determined by the total DC transport current and the penetration field of the conductor. We show that the field-dependence of the normalised magnetisation loss provides an unambiguous value for this threshold field at zero transport current. From this insight we then obtain an expression for the dynamic resistance in perpendicular field. This approach implies a linear relationship between dynamic resistance and applied field amplitude, and also between threshold field and transport current and this is consistent with our experimental data. The analytical expression obtained yields values that closely agree with measurements obtained across a wide range of frequencies and transport currents, and for multiple CC wires produced by different wire manufacturers and with significantly differing dimensions and critical currents. We further show that at high transport currents, the measured DC resistance includes an additional nonlinear term which is due to flux-flow resistance incurred by the DC transport current. This occurs once the field-dependent critical current of the wire falls below the DC transport current for part of each field cycle. Our results provide an effective and simple approach to calculating the dynamic resistance of a CC wire, at current and field magnitudes consistent with those expected in superconducting machines. This is the Accepted Manuscript version of an article accepted for publication in 'Superconductor Science and Technology'. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The Version of Record is available online at https://doi.org/10.1088/1361-6668/aa54e5.

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Dynamic Resistance Measurement of a Four-Tape YBCO Stack in a Perpendicular Magnetic Field

10.26686/wgtn.14337368 ◽

2021 ◽

Author(s):

Zhenan Jiang ◽

W Zhou ◽

Christopher Bumby ◽

M Staines ◽

Q Li ◽

...

Keyword(s):

Magnetic Field ◽

Critical Role ◽

Coated Conductors ◽

Threshold Field ◽

Dynamic Resistance ◽

Perpendicular Magnetic Field ◽

Personal Use ◽

Dc Current ◽

The Magnetic Field ◽

Circulating Currents

Dynamic resistance occurs when HTS (high-temperature superconductor) coated conductors carry dc current under ac magnetic field. This dissipative effect can play a critical role in many HTS applications. Here, we report on dynamic resistance measurements of a four-tape YBCO stack comprising 4-mm-wide coated conductors, which experience an applied ac perpendicular magnetic field with an amplitude of up to 100 mT. Each tape within the stack carries the same dc current. The magnetic field amplitude, the frequency of the magnetic field, and the dc current magnitude are varied to investigate the influence of these parameters on the dynamic resistance. We find that the threshold field of the stack is significantly larger than that of a single tape when dc current is small, which we attribute to coherent shielding effects from circulating currents present in each wire in the stack. © 2018 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.

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Dynamic Resistance Measurement of a Four-Tape YBCO Stack in a Perpendicular Magnetic Field

10.26686/wgtn.14337368.v1 ◽

2021 ◽

Author(s):

Zhenan Jiang ◽

W Zhou ◽

Christopher Bumby ◽

M Staines ◽

Q Li ◽

...

Keyword(s):

Magnetic Field ◽

Critical Role ◽

Coated Conductors ◽

Threshold Field ◽

Dynamic Resistance ◽

Perpendicular Magnetic Field ◽

Personal Use ◽

Dc Current ◽

The Magnetic Field ◽

Circulating Currents

Dynamic resistance occurs when HTS (high-temperature superconductor) coated conductors carry dc current under ac magnetic field. This dissipative effect can play a critical role in many HTS applications. Here, we report on dynamic resistance measurements of a four-tape YBCO stack comprising 4-mm-wide coated conductors, which experience an applied ac perpendicular magnetic field with an amplitude of up to 100 mT. Each tape within the stack carries the same dc current. The magnetic field amplitude, the frequency of the magnetic field, and the dc current magnitude are varied to investigate the influence of these parameters on the dynamic resistance. We find that the threshold field of the stack is significantly larger than that of a single tape when dc current is small, which we attribute to coherent shielding effects from circulating currents present in each wire in the stack. © 2018 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.

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AC Loss Characteristics of Stacks of YBCO Coated Conductors

MRS Proceedings ◽

10.1557/proc-0946-hh10-06 ◽

2006 ◽

Vol 946 ◽

Cited By ~ 3

Author(s):

Francesco Grilli ◽

Stephen P. Ashworth ◽

Svetlomir Stavrev

Keyword(s):

Magnetic Field ◽

Transport Current ◽

Point Of View ◽

Coated Conductors ◽

Ac Loss ◽

Ac Losses ◽

Practical Applications ◽

Superconducting Coils ◽

Loss Characteristic ◽

Ybco Coated Conductors

ABSTRACTPractical applications of YBCO coated conductors (CC) involving superconducting coils will utilize tapes packed together in an arrangement resembling a vertical stack. In such configuration there is an important electromagnetic interaction between the tapes, which strongly influences the loss characteristic of the device.In the presence of an external magnetic field, the losses are reduced compared to an isolated tape because of the reduced aspect ratio of the conductor and, at least for low fields, because of an effective screening of the central part of the stack. On the contrary, in the case of AC transport current, the losses tend to increase due to the enhancement of the local field caused by the interaction of the self-field produced by neighboring tapes. In practical situations the conductor is usually subjected to both transport current and magnetic field, so that there is a trade-off between the two effects.In this paper we investigate, both experimentally and by means of finite-element method calculations, the ac loss behavior of a stack composed by a finite number of tapes in different working conditions, and we compare the AC losses to the ones of non-interacting tapes in order to determine if the use of stacked tapes is advantageous from the point of view of power dissipation.

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The dynamic resistance of YBCO coated conductor wire: Effect of DC current magnitude and applied field orientation

10.26686/wgtn.14331620 ◽

2021 ◽

Author(s):

Zhenan Jiang ◽

W Zhou ◽

Q Li ◽

M Yao ◽

J Fang ◽

...

Keyword(s):

Magnetic Field ◽

Applied Field ◽

Threshold Field ◽

Dynamic Resistance ◽

Coated Conductor ◽

Field Orientation ◽

Ac Magnetic Field ◽

Ybco Coated Conductor ◽

Wide Range ◽

Dc Current

Dynamic resistance, which occurs when a HTS coated conductor carries a DC current under an AC magnetic field, can have critical implications for the design of HTS machines. Here, we report measurements of dynamic resistance in a commercially available SuperPower 4 mm-wide YBCO coated conductor, carrying a DC current under an applied AC magnetic field of arbitrary orientation. The reduced DC current, I t/I c0, ranged from 0.01 to 0.9, where I t is the DC current level and I c0 is the self-field critical current of the conductor. The field angle (the angle between the magnetic field and the normal vector of the conductor wide-face) was varied between 0° and 90° at intervals of 10°. We show that the effective width of the conductor under study is ∼12% less than the physical wire width, and we attribute this difference to edge damage of the wire during or after manufacture. We then examine the measured dynamic resistance of this wire under perpendicular applied fields at very low DC current levels. In this regime we find that the threshold field, B th, of the conductor is well described by the nonlinear equation of Mikitik and Brandt. However, this model consistently underestimates the threshold field at higher current levels. As such, the dynamic resistance in a coated conductor under perpendicular magnetic fields is best described using two different equations for each of the low and high DC current regimes, respectively. At low DC currents where I t/I c0 ≤ 0.1, the nonlinear relationship of Mikitik and Brandt provides the closest agreement with experimental data. However, in the higher current regime where I t/I c0 ≥ 0.2, closer agreement is obtained using a simple linear expression which assumes a current-independent penetration field. We further show that for the conductor studied here, the measured dynamic resistance at different field angles is dominated by the perpendicular magnetic field component, with negligible contribution from the parallel component. Our findings now enable the dynamic resistance of a single conductor to be analytically determined for a very wide range of DC currents and at all applied field angles. This is the Accepted Manuscript version of an article accepted for publication in 'Superconductor Science and Technology'. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The Version of Record is available online at https://doi.org/10.1088/1361-6668/aaa49e.

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Dynamic resistance measurements in a GdBCO-coated conductor

10.26686/wgtn.14384543.v1 ◽

2021 ◽

Author(s):

Zhenan Jiang ◽

R Toyomoto ◽

N Amemiya ◽

Christopher Bumby ◽

Rodney Badcock ◽

...

Keyword(s):

Magnetic Field ◽

Dynamic Resistance ◽

Normal Vector ◽

Coated Conductor ◽

Personal Use ◽

Perpendicular Component ◽

Experimental Values ◽

Dc Current ◽

Heat Loads ◽

The Magnetic Field

Dynamic resistance is a phenomenon which occurs when a superconducting wire carries dc transport current whilst experiencing an alternating magnetic field. This situation occurs in a range of HTS machinery applications, where dynamic resistance can lead to large parasitic heat loads and potential quench events. Here, we present dynamic resistance measurements of a 5-mm-wide Fujikura coated conductor wire at 77 K. We report experimental values obtain through varying the field angle (the angle between magnetic field and normal vector of the conductor wide-face), the dc current levels, and the magnetic field amplitude, and frequency. We show that the dynamic resistance in perpendicular magnetic field can be predicted by using a simple analytical equation. We also show that across the range of field angles measured here the dynamic resistance is dominated by the perpendicular component of the applied magnetic field. © 2017 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.

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