Persistent Current Mode Operation of A 2G HTS Coil With A Flux Pump

Lee, Seyeon; Kim, Woo-Seok; Kim, Yungil; Lee, Ji-Yung; Park, Sang-Ho; Lee, Ji-Kwang; Hong, Gye-Won; Kim, Sung‐Soo; Han, Jin-Yi; Hwang, Young Jin; Choi, Kyeongdal

doi:10.1109/tasc.2016.2524519

Cited by 49 publications

(15 citation statements)

References 5 publications

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“…Through interpreting results from the FE model, we find that both the short-circuit current (I sc ) and the apparent internal resistance (R int ) of the dynamo arise from competition between the net transport current I T and the local circulating eddy currents. This understanding implies that HTS dynamo designs incorporating much wider stators should exhibit improved performance, as has been reported experimentally [9,41].…”

Section: Introductionsupporting

confidence: 54%

“…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%

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

et al. 2020

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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.

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Section: Introductionsupporting

confidence: 54%

Section: Introductionmentioning

confidence: 99%

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

et al. 2020

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“…Jiang and co-workers [26] proposed that dynamic resistance contributes most to the effective resistance and is the limiting factor of saturation current. Lee and co-workers [27] reported that the sheet width strongly influences the saturation current. The magnitude of the voltage observed is proportional to rotating frequency, and the polarity is related to rotating direction and the polarity of the magnets [11]…”

Section: Rotating Magnets Based Travelling Wave Flux Pump (Rtwfp)mentioning

confidence: 99%

An Overview of Flux Pumps for HTS Coils

Coombs

Geng

et al. 2016

IEEE Trans. Appl. Supercond.

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“…HTS flux pumps can inject flux into closed superconducting circuit, making quasi-persistent current mode in closed HTS coils possible. Several types of HTS flux pumps for HTS coils have been developed during recent years, including rotating permanent magnets based flux pumps [12][13][14][15], linear travelling wave flux pumps [16,17], a self-switching flux pump [18], and an AC field controlled transformer-rectifier flux pump [19,20]. Recently, a study on charge-discharge characteristics of no-Insulation GdBCO coils energized by a rotating permanent magnets based flux pump was presented, which verified the feasibility of employing the rotating permanent magnets based flux pump to charge NI coils [21].…”

Section: Introductionmentioning

confidence: 99%

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

Geng

Coombs

2017

Supercond. Sci. Technol.

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：High-Temperature Superconducting (HTS) coils wound from coated conductors without turn-to-turn insulation (NI coils) have been proven with excellent electrical and thermal performances. However, the slow charging of NI coils has been a long lasting problem. In this work, we explore using a transformer-rectifier HTS flux pump to charge an NI coil and a Metal-Insulated (MI) coil. The charging performance comparison is made between different coils. Comprehensive study is done to thoroughly understand the electrical-magnetic transience in charging these coils. We will show that the low-voltage high-current flux pump is especially suitable for charging NI coils with very low characteristic resistance.

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Persistent Current Mode Operation of A 2G HTS Coil With A Flux Pump

Cited by 49 publications

References 5 publications

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

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

An Overview of Flux Pumps for HTS Coils

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

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