Modeling methodology for a HTS flux pump using a 2D <i>H</i>-formulation

Geng, Jianzhao; Coombs, Tim

doi:10.1088/1361-6668/aae4bc

Cited by 37 publications

(33 citation statements)

References 31 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The mechanism here should have some bearing on the mechanism of other flux pumps. For HTS rectifier-type flux pumps, Geng and Coombs [19] give an explanation in terms of flux linkage and the movement of the electric central line. As the HTS rectifier is based on a dynamic resistance switch that rectifies an applied ac emf, the movement of the central line of the electric field is very much akin to the movement of the electric field distributions in Fig.…”

Section: A Origin Of the DC Voltage V Ocmentioning

confidence: 99%

“…High-T c superconducting (HTS) dynamos [1][2][3][4][5][6][7][8][9][10][11][12][13] and other similar HTS "flux pumps" [14][15][16][17][18][19][20][21][22] have been receiving continuing attention recently, as they offer a potential solution to the dc current-injection problem in a wide range of superconducting machines [23] and magnets [24,25]. Specifically, the HTS dynamo is of interest for its predicted output produced by a HTS dynamo arises naturally from Maxwell's laws [12] when applied to a situation in which eddy currents flow in a thin sheet exhibiting a highly nonlinear local resistivity.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Mechanism of the High- Tc Superconducting Dynamo: Models and Experiment

et al. 2020

View full text Add to dashboard Cite

High-T c superconducting (HTS) dynamos are experimentally proven devices that can produce large (more than a kiloamp) dc currents in superconducting circuits, without the thermal leak associated with copper current leads. However, these dc currents are theoretically controversial, as it is not immediately apparent why a device that is topologically identical to an ac alternator should give a dc output at all. Here, we present a finite-element model and a comparison of it with experiment that fully explain this effect. It is shown that the dc output arises naturally from Maxwell's laws when time-varying overcritical eddy currents are induced to circulate in a HTS sheet. We first show that our finite-element model replicates all of the experimental electrical behavior reported so far for these devices, including the dc output characteristics and transient electrical waveforms. Direct experimental evidence for the presence of circulating eddy currents is also obtained through measurements of the transient magnetic field profile across the HTS tape, using a linear Hall array. These results are also found to agree closely with predictions from the finite-element model. Following this experimental validation, calculated sheet current densities and the associated local electric fields are examined for a range of frequencies and net transport currents. We find that the electrical output from a HTS dynamo is governed by the competition between transport and eddy currents induced as the magnet transits across the HTS tape. The eddy currents are significantly higher (approximately 1.5 times) than the local critical current density, and hence experience a highly nonlinear local resistivity. This nonlinearity breaks the symmetry observed in a normal ohmic material, which usually requires the net transport current to vary linearly with the average electric field. The interplay between local current densities and nonlinear resistivities (which both vary in time and space) is shown to systematically give rise to the key observed parameters of experimental HTS dynamo devices: the open-circuit voltage, the internal resistance, and the short-circuit current. Finally, we identify that the spatial boundaries formed by each edge of the HTS stator tape play a vital role in determining the total dc output. This offers the potential to develop alternative designs for HTS dynamo devices, in which the internal resistance is greatly reduced and the short-circuit current is substantially increased.

show abstract

Section: A Origin Of the DC Voltage V Ocmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Mechanism of the High- Tc Superconducting Dynamo: Models and Experiment

et al. 2020

View full text Add to dashboard Cite

show abstract

“…However, since they have used stationary sinusoidal ac magnetic field as external applied magnetic field, the case is totally different with external magnetic field due to the moving magnet, so these models cannot provide a realistic model of the mechanism of a dynamo-type flux pump. In [58], a transformer-rectifier HTS flux pump was modeled in COMSOL using a 2D H-formulation and verified by experimental data. It was demonstrated how dynamic resistance is created using traveling magnetic field.…”

Section: Introductionmentioning

confidence: 99%

Modeling of airgap influence on DC voltage generation in a dynamo-type flux pump

Ghabeli

Pardo

2020

Supercond. Sci. Technol.

View full text Add to dashboard Cite

show abstract

“…Using this dc voltage, this inherently superconducting device can inject dc current into a superconducting coil, without the use of copper current leads and their associated losses [26]. The origin of the rectification effect in the HTS dynamo is not trivial to explain, as unlike a bridge rectifier device [4], [13], [17], [18], HTS dynamos do not include a separate switching element. Instead, a simple dynamo only has a single circuit element, namely the stator wire itself.…”

Section: Introductionmentioning

confidence: 99%

Modeling of Stator Versus Magnet Width Effects in High-$T_c$ Superconducting Dynamos

Mataira

Ainslie

Badcock

et al. 2020

IEEE Trans. Appl. Supercond.

View full text Add to dashboard Cite

High-Tc superconducting (HTS) dynamos are simple devices for injecting and sustaining dc currents in superconducting coils/magnets. The simple geometry of these devices consists of a superconducting stator(s) and one or more rotor magnets arranged in identical fashion to a classical alternator. However, unlike the classical alternator, the HTS dynamo gives a selfrectified dc output. This somewhat anomalous result is caused by the non-linear resistivity of HTS materials and the large over-critical eddy currents that flow in the stator. As these overcritical currents must recirculate in the HTS stator, the stator's width becomes a key parameter in the physics of the device. In this work we explore the effect of increasing the stator width through using recent advances in modeling these systems. We find that given enough space in the stator, the total sum of circulating and transport currents do not drive the full width of the stator into the flux-flow regime. Operation of the device in this regime results in a non-linear I-V curve, a marked decrease in the internal resistance at open circuit Roc, a saturation of the open circuit voltage Voc, and a short-circuit current Isc that approaches the in-field critical current of the stator itself Ic,min. These behaviors lead to the conclusion that optimal HTS dynamo design should ensure that the stator width be sufficient to avoid current saturation of the superconductor at the target operating current .

show abstract

Modeling methodology for a HTS flux pump using a 2D H-formulation

Cited by 37 publications

References 31 publications

Mechanism of the High- Tc Superconducting Dynamo: Models and Experiment

Mechanism of the High- Tc Superconducting Dynamo: Models and Experiment

Modeling of airgap influence on DC voltage generation in a dynamo-type flux pump

Modeling of Stator Versus Magnet Width Effects in High-$T_c$ Superconducting Dynamos

Contact Info

Product

Resources

About