The possibility of using high-T<sub>c</sub>superconducting films as elements of a rectifier

Vysotsky, V.S.; Karasik, V.R.; Pechen, E. V.; Lebedev, P. N.; Markovsky, N.V.; Shevchenko, O.A.

doi:10.1088/0953-2048/3/5/009

Cited by 14 publications

(7 citation statements)

References 6 publications

(2 reference statements)

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“…It was shown recently in Mataira et al [7,8] that the open-circuit voltage can be explained well -most importantly, with good quantitative agreement -using classical electromagnetic theory. The DC output voltage obtained from an HTS dynamo arises naturally from a local rectification effect caused by overcritical eddy currents [7][8][9][10][11][12]: an effect that has been observed in HTS materials as far back as Vysotsky et al [13]. The gap dependence of the open-circuit voltage computed by Ghabeli and Pardo [14] also agrees with experiments.…”

Section: Introductionsupporting

confidence: 71%

Modelling the Frequency Dependence of the Open-Circuit Voltage of a High-T _c Superconducting Dynamo

Ainslie

Quéval

Mataira

et al. 2021

IEEE Trans. Appl. Supercond.

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A high-Tc superconducting (HTS) dynamo enables the injection of large DC currents into a superconducting circuit, without the requirement for current leads. In this work, we attempt to explain the frequency dependence of such dynamos/flux pumps reported in the literature, where it is observed that the rate at which the open-circuit DC voltage increases reduces with increasing frequency, in contrast to the expected linear behaviour. Heat generated in the HTS wire has been the common explanation given to date for this phenomenon. Here we offer an alternative explanation: the interaction between and current flow in the different layers of the HTS wire as the frequency of the dynamo increases. Our claim is based on numerical analysis using a segregated H-formulation finite-element model of the HTS dynamo benchmark problem that is extended to include the full HTS wire architecture and coupled with a thermal model. This framework enables us to efficiently model the relative movement between the rotating room-temperature permanent magnet and the stationary HTS wire and to study the impact of the frequency of rotation and temperature on the open-circuit DC voltage of the dynamo.

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Section: Introductionsupporting

confidence: 71%

Modelling the Frequency Dependence of the Open-Circuit Voltage of a High-T _c Superconducting Dynamo

Ainslie

Quéval

Mataira

et al. 2021

IEEE Trans. Appl. Supercond.

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“…It was shown recently in Mataira et al [14,15] that the behaviour of the HTS dynamo can be explained well-most importantly, with good quantitative agreement-using classical electromagnetic theory. The DC output voltage obtained from an HTS dynamo arises naturally from a local rectification effect caused by overcritical eddy currents flowing within the HTS wire [6-8, 14, 16]: a classical effect that has been observed in HTS materials as far back as Vysotsky et al [17]. The gap dependence of the open-circuit voltage computed by Ghabeli and Pardo [18] also agrees with experiments.…”

Section: Introductionmentioning

confidence: 60%

“… n E (16) This gives a solution where the flux of the magnet is completely enclosed in the rotor domain and H = 0 elsewhere. By the principle of superposition, it must be the case that the field of the PM is contained inside the boundary ∂Ω R by a shell current, K shell , on this boundary, that produces the opposite PM field outside the boundary, i.e., H m + H shell = 0.…”

Section: H-formulation + Shell Current (H+sc)mentioning

confidence: 99%

A new benchmark problem for electromagnetic modelling of superconductors: the high-T _c superconducting dynamo

Ainslie

Grilli

Quéval

et al. 2020

Supercond. Sci. Technol.

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The high-T c superconducting (HTS) dynamo is a promising device that can inject large DC supercurrents into a closed superconducting circuit. This is particularly attractive to energise HTS coils in NMR/MRI magnets and superconducting rotating machines without the need for connection to a power supply via current leads. It is only very recently that quantitatively accurate, predictive models have been developed which are capable of analysing HTS dynamos and explain their underlying physical mechanism. In this work, we propose to use the HTS dynamo as a new benchmark problem for the HTS modelling community. The benchmark geometry consists of a permanent magnet rotating past a stationary HTS coated-conductor wire in the open-circuit configuration, assuming for simplicity the 2D (infinitely long) case. Despite this geometric simplicity the solution is complex, comprising time-varying spatially-inhomogeneous currents and fields throughout the superconducting volume. In this work, this benchmark problem has been implemented using several different methods, including H-formulation-based methods, coupled H-A and T-A formulations, the Minimum Electromagnetic Entropy Production method, and integral equation and volume integral equation-based equivalent circuit methods. Each of these approaches show excellent qualitative and quantitative agreement for the open-circuit equivalent instantaneous voltage and the cumulative time-averaged equivalent voltage, as well as the current density and electric field distributions within the HTS wire at key positions during the magnet transit. Finally, a critical analysis and comparison of each of the modelling frameworks is presented, based on the following key metrics: number of mesh elements in the HTS wire, total number of mesh elements in the model, number of degrees of freedom, tolerance settings and the approximate time taken per cycle for each model. This benchmark and the results contained herein provide researchers with a suitable framework to validate, compare and optimise their own methods for modelling the HTS dynamo.

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“…This approach does not rely on a separate rectifying 'switch' component which simplifies the architecture of transformerdriven LTS flux pumps. In later work, Vyssotsky et al [50] proposed using HTS thin film as the switching element in a similar type of device, through exploiting the highly nonlinear E-J resistivity of these materials [51]. Subsequently, Geng et al [52] have demonstrated this approach, in an HTS self-rectifier which used a coated conductor wire as a noninductive bridge, and was capable of delivering a maximum ouput current of ∼80 A.…”

Section: Introductionmentioning

confidence: 99%

Maximising the current output from a self-switching kA-class rectifier flux pump

Geng

Bumby

Badcock

2020

Supercond. Sci. Technol.

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High current operation of HTS magnets is desirable for many applications, but operating currents are typically limited by resistive heating of the normal-conducting current leads, which connect the cryogenic magnet coil to a room-temperature electronic power supply. Rectifying flux pumps are a feasible alternative solution as they enable current to be directly injected into the HTS magnet coil via a closed superconducting circuit. In this work, we have developed and demonstrated two prototype HTS self-rectifying flux pump devices capable of delivering very high output currents. One of these devices can deliver a maximum direct current of >2 kA. This is a new record for the flux pump excitation of an HTS coil. Unlike other rectifying flux pumps, the self-rectifying flux pumps reported here do not employ an active switching component. Instead passive 'self-switching' rectification is achieved by applying an assymmetric current waveform to the primary winding. This significantly reduces the complexity of the system compared to other flux pump architectures, and removes the need for dissipative electronic components within the cryogenic environment. We demonstrate that these devices also function when the iron core linking the superconducting secondary and the normal conducting primary is broken by a pair of air gaps. In these conditions DC currents of >600 A can be maintained with a total air gap length of 10 mm. This indicates that this approach represents a feasible practical solution for through-wall excitation of high current HTS magnets.

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The possibility of using high-T_csuperconducting films as elements of a rectifier

Cited by 14 publications

References 6 publications

Modelling the Frequency Dependence of the Open-Circuit Voltage of a High-T _c Superconducting Dynamo

Modelling the Frequency Dependence of the Open-Circuit Voltage of a High-T _c Superconducting Dynamo

A new benchmark problem for electromagnetic modelling of superconductors: the high-T _c superconducting dynamo

Maximising the current output from a self-switching kA-class rectifier flux pump

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The possibility of using high-Tcsuperconducting films as elements of a rectifier

Cited by 14 publications

References 6 publications

Modelling the Frequency Dependence of the Open-Circuit Voltage of a High-T c Superconducting Dynamo

Modelling the Frequency Dependence of the Open-Circuit Voltage of a High-T c Superconducting Dynamo

A new benchmark problem for electromagnetic modelling of superconductors: the high-T c superconducting dynamo

Maximising the current output from a self-switching kA-class rectifier flux pump

Contact Info

Product

Resources

About

The possibility of using high-T_csuperconducting films as elements of a rectifier

Modelling the Frequency Dependence of the Open-Circuit Voltage of a High-T _c Superconducting Dynamo

Modelling the Frequency Dependence of the Open-Circuit Voltage of a High-T _c Superconducting Dynamo

A new benchmark problem for electromagnetic modelling of superconductors: the high-T _c superconducting dynamo