Numerical Modeling and Experimental Analysis of AC Critical Current in YBCO-Coated Conductors

Liu, Hongwei; Li, Guangxi; Zhang, Huiyuan; Wang, Yinshun

doi:10.1109/tasc.2014.2365109

Cited by 5 publications

(2 citation statements)

References 14 publications

(16 reference statements)

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“…Considering the H-formulation, the previous works dedicated to the validation of the model only contrasted the calculated results with measurements provided by a mean value of the current distribution, which represents an indirect comparison. Generally, the results are presented with good agreement [4,[13][14][15][16] for the energy dissipated (power losses) in a superconducting tape transporting an AC current. Also, the Hformulation by FEM simulations was successfully compared with levitation force measurements [17].…”

Section: Comsolmentioning

confidence: 74%

H-Formulation FEM Modeling of the Current Distribution in 2G HTS Tapes and Its Experimental Validation Using Hall Probe Mapping

Sotelo

Carrera

Lopez-Lopez

et al. 2016

IEEE Trans. Appl. Supercond.

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One of the most widespread mathematical formulations applied to simulate the electromagnetic phenomena of coated conductor in the recent literature is the H one. However, the only validation of the model has been indirect by using measurements taken from the applications, as measurements of the energy losses in ac fields, forces developed in levitation systems or any other parameter related to a specific application. Direct validation of the calculation requires the observation of the local out of plane magnetic field over the surface of the sample and this is only accessible under magnetooptical observations and, in a larger scale and better dynamic range, by the Hall scanning microscopy. We propose here the experimental validation of the Hformulation by comparing the simulated results with measurements made by a Hall probe mapping in a second generation (2G) tape sample for several DC transported currents at 77 K. The paper presents a methodology to simulate the 2G tape by using only measured data obtained from a sample and its normalized J(B) experimental curves. Some boundary conditions that allow a faster convergence of the problem are investigated. Simulated results of the 2G tape modelled considering only the 1 µm HTS layer were compared with other that represent the most important layers of the coated conductor structure in the calculations. The simulated and measured results present a good agreement, proving that this model can calculate precisely the magnetic field and, hence, the current distribution in HTS samples.

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Section: Comsolmentioning

confidence: 74%

H-Formulation FEM Modeling of the Current Distribution in 2G HTS Tapes and Its Experimental Validation Using Hall Probe Mapping

Sotelo

Carrera

Lopez-Lopez

et al. 2016

IEEE Trans. Appl. Supercond.

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show abstract

“…It has been previously reported that the measured I-V characteristics of HTS tapes are sensitive to the rate at which current is injected into the material [112][113][114][115] in both thin film and cylindrical wire geometries. In that work an analytic model has been presented in which the electric field in the edge regions can be several orders of magnitude larger than at the tape centre.…”

Section: Fe Modelling Of I Cs At Different Ramp Ratesmentioning

confidence: 99%

Modelling of Saturation Currents and Dynamic Resistance in High-Temperature-Superconductors

Brooks¹

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High temperature coated conductors are useful for their large Tc, Jc and Bc2values. They are manufactured in long lengths and are available from numerouscommercial distributors around the world. As a result, they have found use inmany applications that can utilise the large magnetic fields that these materialscan produce. In any complex circuit that incorporates superconducting components, it can bedesirable to include superconducting analogues of semiconducting power electronics,such as switches, and transistors. The ideal switch in a superconducting circuit haszero resistance when the switch is closed and infinite resistance when open. Onlysuperconductors can provide the zero resistance closed state. Thus it is the onset ofresistive phenomenon, the conditions under which a non zero resistance is inducedin a superconducting tape, stack, or loop, that are the subject of this thesis. The two phenomena that are examined are: geometric current saturation, and dynamicresistance. Both are investigated using existing finite element models employing the H-formulation and a power-law resistivity in the software COMSOL, accompaniedby experimental verification. Flux flow resistance arises when the transport current in a high temperature superconductor is larger than the critical current I c. This current produces asufficiently large Lorentz force such that there is continuous vortex motion through the superconductor. This results in an effective DC resistance. Today, the criticalcurrent is universally identified using an arbitrary voltage measurement criterion. In this thesis, it is demonstrated that current filling and eventual saturation acrossthe width of a HTS tape can be observed using magnetic field imaging near to the tape surface and correlated with changes in the measured I-V characteristics. Asimple model is presented to explain this behaviour which requires only that the material have a non-linear resistivity. The current filling behaviour is modelledusing numerical methods and validated against experimental data obtained from commercial wires. Finally, it is shown that the saturation determined using eithermagnetic field imaging or voltage measurements is sensitive to the rate of change of current. Dynamic resistance is a resistive phenomenon that occurs when an AC magnetic field interacts with a high temperature superconductor that is simultaneously carrying aDC transport current lower than the critical current. Dynamic resistance occurs when the AC field amplitude is larger than some sample dependent threshold. Comparison between numerical models and measured data demonstrate that field dependent Jc values are required to reproduce the experimentally observed transientvoltage waveforms. The finite element models were then used to analyse the transient current distributions inside of vertical stacks of parallel connected tapesand predict values for the threshold magnetic field. The threshold fields exhibit a transition from ’tape-like’ to ’slab-like’ behaviour as the stack aspect ratio varies. Finally, the effective resistance of a current carrying hollow superconducting strip exposed to an alternating perpendicular magnetic field is presented and analysedvia finite element modelling.

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Study of AC Loss and Temperature Distribution of a BSCCO Coil Cooled in Liquid Nitrogen or Using a Cryocooler

Lai

et al. 2016

IEEE Trans. Appl. Supercond.

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Numerical Modeling and Experimental Analysis of AC Critical Current in YBCO-Coated Conductors

Cited by 5 publications

References 14 publications

H-Formulation FEM Modeling of the Current Distribution in 2G HTS Tapes and Its Experimental Validation Using Hall Probe Mapping

H-Formulation FEM Modeling of the Current Distribution in 2G HTS Tapes and Its Experimental Validation Using Hall Probe Mapping

Modelling of Saturation Currents and Dynamic Resistance in High-Temperature-Superconductors

Study of AC Loss and Temperature Distribution of a BSCCO Coil Cooled in Liquid Nitrogen or Using a Cryocooler

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