Effects of turn-to-turn compactness in the straight sections of HTS racetrack coils on thermal and electrical characteristics

Kwon, Ohin; Kim, K L; Choi, Yoon Hyuck; Shin, Hyun Jin; Hahn, Seungyong; Iwasa, Y.; Lee, H G

doi:10.1088/0953-2048/26/8/085025

Cited by 54 publications

(10 citation statements)

References 23 publications

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“…As expected, although the supply current decreased to 0 A, the B z still remained due to discharging delay in the NI coil [12][13][14][15]. The onset values of B z measured at R d = 1 A s −1 and I op = 60, 70, 80, and 90 A were 4.5, 4.7, 4.8, and 4.8 mT, and those at R d = 10 A s −1 were 32.3, 35.6, 36.4, and 39.9 mT, respectively.…”

Section: Resultssupporting

confidence: 75%

“…However, the time constant of the non-insulated (NI) HTS magnet is much higher than that of a completely insulated magnet due to the generation of a non-superconducting current path by the absence of insulation, which leads to a low magnet charge/discharge rate [12][13][14][15][16]. Accordingly, the applied-field history dependency of an SCIF may be more remarkable due to the turn-to-turn contact.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Screening current-induced field in non-insulated GdBCO pancake coil

Yang

Kim

Choi

et al. 2013

Supercond. Sci. Technol.

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In this study, empirical and numerical analyses on the screening current-induced field (SCIF) characteristics of a non-insulated (NI) GdBCO-coated conductor single-pancake coil were conducted. Charge and discharge tests were carried out to induce an SCIF in the NI test coil. The SCIF in the NI coil was identified by comparison between the measured and calculated magnetic fields. The experimental results exhibit an increase of the SCIF with increasing an operating current, as well as a logarithmic decay of the SCIF as a function of time. Moreover, the SCIF was not affected by the slow discharge of the NI coil. The estimation of the SCIF based on the critical-state model in a thin film using the finite element method was in fairly good agreement with the experimental results.

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Section: Resultssupporting

confidence: 75%

Section: Introductionmentioning

confidence: 99%

Screening current-induced field in non-insulated GdBCO pancake coil

Yang

Kim

Choi

et al. 2013

Supercond. Sci. Technol.

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“…Hence, if the dedicated electrical insulation can be omitted, there may be significant cost savings and thermal stability improvements. Although there have recently been growing interest of no-insulation coils [21]- [23], allowing direct metal-to-metal contact between turns, this may not be an option due to the long energizing times. Instead, the epoxy attached to the MgB2 wire during winding is used for electrical insulation between turns [24].…”

Section: Coil Fabrication Methodologymentioning

confidence: 99%

Fabrication of a Scaled MgB2 Racetrack Demonstrator Pole for a 10-MW Direct-Drive Wind Turbine Generator

Magnusson

Eliassen

Abrahamsen

et al. 2018

IEEE Trans. Appl. Supercond.

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Abstract-Field windings made of MgB2 wires or tapes are considered for their potential to reduce volume, weight and cost of large offshore wind turbine generators. To gain experience of how to use this relatively new material in full-scale generators, tests of different winding methodologies and techniques are needed. In this paper, we describe in detail the steps used to wind a racetrack coil with a length of 1 m and a width of 0.5 m out of 4.5 km of MgB2 superconducting tape. The width corresponds to a full-scale pole of a 10 MW generator, whereas the length of the straight section is shorter than the corresponding full-scale pole. The coil was built up of 10 double pancake coils. Each double pancake coil was wet-wound using a semi-automatic winding process, where Stycast 2850 was applied directly to the MgB2 tape without any other dedicated electrical insulation. The strengths and weaknesses of the winding process are discussed and compared to the dry-winding method. 

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“…Almost all studies of NI coils to date have implicitly adopted this assumption. This assumption is rough since TTRD is actually affected by turn-to-turn contact pressure [1,2]. However, some studies [2] have shown that when the contact pressure exceeds a certain value, the TTRD becomes less sensitive to it.…”

Section: Introductionmentioning

confidence: 99%

“…In recent years, an increasing number of studies have reported that setting only a uniform TTRD in simulation models is not sufficient to accurately predict the behaviour of NI coils in experiments [18,[24][25][26]. In fact, the TTRD of NI coils is affected by various factors including surface condition [27], temperature [12], number of thermal cycles [2] and turn-to-turn contact pressure [1] which is influenced by winding tension [28], thermal stress [28] and electromagnetic force [29]. Some studies [28,[30][31][32][33] have shown that even if the coil is wound with uniform pre-stress, the TTRD of the coil still exhibits a non-uniform distribution.…”

Section: Introductionmentioning

confidence: 99%

A non-destructive method for detecting turn-to-turn resistivity distribution in NI REBCO coils

Wu,

Lu,

Zhong

et al. 2023

Supercond. Sci. Technol.

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A non-destructive method is proposed for detecting the turn-to-turn resistivity distribution (TTRD) of non-insulation (NI) coils made of REBCO tapes. In conventional designs, TTRD is often estimated to be a constant, while it is actually non-uniform. However, it is crucial to detect more accurate TTRD of NI coils as it determines the behaviour of NI coils and may lead to peculiar phenomena such as local reverse currents.The proposed approach involves acquiring the temporal change of voltage distribution during an excitation/demagnetization process, which is subsequently incorporated to a system of ordinary differential equations established derived from an equivalent circuit model. A genetic algorithm (GA) is then employed to fit the collected time-varying voltage data and generate the results of “measured” TTRD. The system of equations can actually be numerically solved. The solved time-varying TTRD results are averaged over the measuring period, which serve as the initial value of GA fitting, and accelerate the fitting process.Virtual measurements were performed on an artificially established mock coil, demonstrating high accuracy in reproducing the predetermined TTRD. Furthermore, an actual measurement was also conducted on a single-pancake coil, however with unknown TTRD, using 8 voltage measurement points during a demagnetization process. The measured TTRD was incorporated into the equivalent circuit model to predict the temporal changes in voltage and magnetic field of the coil under additional excitation/demagnetization conditions. By comparing the predicted results with the experimental data, a high level of agreement was observed, thus confirming the potential application of the proposed method.

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Effects of turn-to-turn compactness in the straight sections of HTS racetrack coils on thermal and electrical characteristics

Cited by 54 publications

References 23 publications

Screening current-induced field in non-insulated GdBCO pancake coil

Screening current-induced field in non-insulated GdBCO pancake coil

Fabrication of a Scaled MgB2 Racetrack Demonstrator Pole for a 10-MW Direct-Drive Wind Turbine Generator

A non-destructive method for detecting turn-to-turn resistivity distribution in NI REBCO coils

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