Flux pumping for non-insulated and metal-insulated HTS coils

Ma, Jun; Geng, Jianzhao; Coombs, Tim

doi:10.1088/1361-6668/aa99f2

Cited by 44 publications

(15 citation statements)

References 27 publications

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“…The DC voltage arises from the interaction between the transport DC current and moving magnetic fluxons within the superconductor, which is a modulation of the vortex spatial distribution [4]. Dynamic resistance is very useful and is utilized as a key mechanism in persistent current switches [7][8][9][10] and HTS flux pumps [11][12][13][14][15][16][17][18][19][20][21][22]. It is also very common for a DC carrying coated conductor to work in an external AC magnetic field, such as in HTS motors and generators [23][24][25][26], levitation [27,28], and HTS power cables [29][30][31].…”

Section: Introductionmentioning

confidence: 99%

A temperature-dependent multilayer model for direct current carrying HTS coated-conductors under perpendicular AC magnetic fields

Geng

Chan

et al. 2020

Supercond. Sci. Technol.

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When a type II superconductor carrying a direct current is subjected to a perpendicular oscillating magnetic field, a direct current (DC) voltage will appear. This voltage can either result from dynamic resistance effect or from flux flow effect, or both. The temperature variation in the superconductor plays an important role in the nature of the voltage, and there has been little study of this so far. This paper presents and experimentally verifies a 2D temperature-dependent multilayer model of the second generation (2G) high temperature superconducting (HTS) coated conductors (CC), which is based on H-formulation and a general heat transfer equation. The model has coupled the electromagnetic and thermal physics, and it can simulate the behavior of 2G HTS coated conductors in various working conditions where the temperature rise has a significant impact. Representative electromagnetic phenomena such as the dynamic resistance effect and the flux flow effect, and thermal behavior like quench and recovery have been simulated. This thermal-coupled model is a powerful tool to study the thermal-electromagnetic behaviors of 2G HTS coated conductors in different working conditions, especially when the impact of temperature rise is important. This multilayer model is also very useful in analyzing the impact of different layers in the 2G HTS CCs, especially the metal stabilizer layers. It has been proven to be a very powerful tool to help understand more complicated characteristics in the CCs which could not be accurately measured or simulated by previous numerical models. The work is indicative and very useful in designing ac magnetic field controlled persistent current switches and flux pumps, in terms of increasing the off-state resistance, analyzing different sources of losses, minimizing detrimental losses, and enhancing the safety and stability.

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Section: Introductionmentioning

confidence: 99%

A temperature-dependent multilayer model for direct current carrying HTS coated-conductors under perpendicular AC magnetic fields

Geng

Chan

et al. 2020

Supercond. Sci. Technol.

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“…During recent years, there has been significant progress in research into HTS flux pumps and related areas, including revealing the rectifying effect [12][13][14][15][16][17][18], understanding the dynamic resistance [19][20][21][22], developing various types of flux pump devicess [23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40], superconducting switches [41,42], cryogenic rectifiers [43,44], multi-pulse magnetizations [45,46], and flux transformation [47].…”

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 basic formula for the resistance is R = ρL/A, where ρ is the resistivity, A is the surface area and L the length along which the current is flowing. For an annular configuration as the small solenoid, where the resistive current flows radially through the annulus, this formula then becomes by integration: R r,ii = ρ coil * ln (r i+1 /r i ) /2πw, (6) where R r,ii are the diagonal elements of the resistance matrix, r i is the radius of the i th turn, and w is the width of the tape. For sections B and C, the network model shows good agreement with the measured data.…”

Section: B Current Step and Overshootmentioning

confidence: 99%

“…"Dry-wound", where there is no insulation material between the turns and the copper coatings of adjacent ReBCO tapes are directly in contact [3]. "Soldered", where solder is added between the turns [4]- [6]. "Metal-insulated", where a metal strip is co-wound between the tapes [7]- [10].…”

mentioning

confidence: 99%

Effective Time Constants at 4.2 to 70 K inReBCO Pancake Coils With Different Inter-Turn Resistances

Nes

Rijk

Kirby

et al. 2022

IEEE Trans. Appl. Supercond.

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For future ReBCO tape based accelerator magnets it is proposed to use no-or partial inter-turn insulation to deal with quench detection and protection. In a non-insulated coil the turns are separated by a finite electrical resistance, providing a bypass for the current at hot-spots, improving thermal stability and quench detection time. However, such coils show different dynamic electromagnetic behavior compared to insulated coils under normal charging and transient quench conditions. To study such coils in detail two pancake coils, one dry-wound and one with solder in between turns, are prepared and tested in a variable temperature cryostat between 4.2 and 70 K. Properties of the coils that are studied are charge and discharge time behavior, turn-to-turn resistance, response to current stepping, and operational stability. In this paper, the first results are presented and compared to a simplified network model in order to gain further understanding into the underlying physics.

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Flux pumping for non-insulated and metal-insulated HTS coils

Cited by 44 publications

References 27 publications

A temperature-dependent multilayer model for direct current carrying HTS coated-conductors under perpendicular AC magnetic fields

A temperature-dependent multilayer model for direct current carrying HTS coated-conductors under perpendicular AC magnetic fields

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

Effective Time Constants at 4.2 to 70 K inReBCO Pancake Coils With Different Inter-Turn Resistances

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