Thermal-electromagnetic modeling of superconductors

Abstract. In this work we study, both experimentally and numerically, the self-heating of a bulk, large YBCO pellet of aspect ratio (thickness / diameter) ~ 0.4 subjected to a large AC magnetic field. To ensure accurate temperature measurements, the sample was placed in an experimental vacuum chamber to achieve a small and reproducible heat transfer coefficient between the superconductor and the cryogenic fluid. The temperature was measured at several locations on the sample surface during the self-heating process. The experimentally determined temperature gradients are found to be very small in this arrangement (< 0.2 K across the radius of the superconductor). The time-dependence of the average temperature T(t) is found to agree well with a theoretical prediction based on the one-dimensional (1-D) Bean model, assuming a uniform temperature in the sample. A 2-D magneto-thermal model was also used to determine the space and time-dependent temperature distribution T (r, z, t) during the application of the AC field. The losses in the bulk pellet were determined using an algorithm based on the numerical method of Brandt, which was combined with a heat diffusion algorithm implemented using a finite-difference method. The model is shown to be able to reproduce the main trends of the observed temperature evolution of the bulk sample during a self-heating process. Finally, the 2-D model is used to study the effect of a non-uniform distribution of critical current density J c (r, z) on the losses within the bulk superconductor.

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“…A field dependence n(B), however, can be introduced to the model, as considered, for example, in ref. [40][41][42].…”

Section: Distribution Of Ac Losses At a Constant Temperaturementioning

confidence: 99%

Self-heating of bulk high temperature superconductors of finite height subjected to a large alternating magnetic field

Laurent¹,

Fagnard²,

Babu³

et al. 2010

Supercond. Sci. Technol.

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“…They may also be applied as the approximate estimation for the hot spot location analyses that are the most crucial ones in transformer modeling. Finally, these already published models and procedures may be used as components of coupled approaches [15,26,44,49,97]. Such thermal-electromagnetic couplings appeared to be the most accurate for the temperature field predictions in all type of transformers.…”

Section: Background Of Coupled Cfd-electromagnetic Solutionsmentioning

confidence: 97%

“…Most of the authors [44,49,97] determine the hot spot value, its location and the whole temperature distribution within the device using this type of equation only. As a result, the temperature field in the solid parts of the transformer and its tank is analysed.…”

Section: Mathematical Model Of Flow and Heat Transfer Problemmentioning

confidence: 99%

“…Most of the papers describing the coupled thermal and electromagnetic problems within electrical transformers consider the heat conduction equation [15,26,44,49,97]. This kind of problem can be calculated using many numerical techniques.…”

Section: Solution Strategy For the Cfd Analysismentioning

confidence: 99%

“…In the relevant literature, the coupling procedure includes similar steps [89,97] that can be summarized as follows: the analysis starts from the computations of the CFD task. The mathematical model required to solve the thermal-flow problem includes the governing equations, source terms, material properties and boundary conditions.…”

Section: General Procedures For Coupling Of Cfd-electromagnetic Solutionsmentioning

confidence: 99%

See 2 more Smart Citations

Numerical Simulation and Experimental Validation of Coupled Flow, Heat Transfer and Electromagnetic Problems in Electrical Transformers

Smołka

Bíró

Nowak

2009

Arch Computat Methods Eng

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The paper presents a state-of-the-art of the numerical modeling of the coupled problems involving heat, fluid flow and electromagnetic phenomena in electrical transformers. Mathematical descriptions of both Computational Fluid Dynamics (CFD) and electromagnetic (EMAG) models are given. Since these models include other submodels for a definition of boundary conditions as local and temperature-dependent convective and radiative heat fluxes, heat generation terms, temperature-dependent and effective values of material properties for different constructions of coils etc., the component problems published in a subject literature are also reported. Moreover, a coupling procedure of the CFD and EMAG solutions to examine the specific power losses within coils and a core is outlined. On the basis of the mathematical model, a numerical example of a three phase medium-power dry-type electrical transformer is presented. A validation of the numerical calculations is performed using the experimental transformer temperature tests in the short-circuit, open-circuit, and under rated parameters according to the current European Standards for dry-type transformers. During the tests, temperatures were measured at selected points on transformer elements using thermocouples and thermometers, while on the external tank walls an infrared thermography was employed.

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Dynamic Electromagnetic Behaviors of High-Temperature Superconductor Levitation System Based on YBCO Material from 3D Perspective

Feng

et al. 2019

J Supercond Nov Magn

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Thermal-electromagnetic modeling of superconductors

Cited by 17 publications

References 10 publications

Self-heating of bulk high temperature superconductors of finite height subjected to a large alternating magnetic field

Self-heating of bulk high temperature superconductors of finite height subjected to a large alternating magnetic field

Numerical Simulation and Experimental Validation of Coupled Flow, Heat Transfer and Electromagnetic Problems in Electrical Transformers

Dynamic Electromagnetic Behaviors of High-Temperature Superconductor Levitation System Based on YBCO Material from 3D Perspective

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