Calculation of AC loss in coated conductor coils with a large number of turns

Pardo, Enric

doi:10.1088/0953-2048/26/10/105017

Cited by 42 publications

(45 citation statements)

References 36 publications

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“…The current constrain is set by fixing the integral in the axial direction of the current density J. For our case, it is enough to approximate the real pancake by another one with lower number of turns (n eff ), one element per turn, no separation between turns, the same radial thickness, and effective transport current I eff = nI/n eff , where n is the number of turns in one pancake and I is the coil net current [10].…”

Section: Methodsmentioning

confidence: 99%

“…The problem of this approximation is that the neighboring turns shield the background magnetic field, in a similar way as in a stack of tapes [8,9]. This shielding effect is very important in windings consisting on stacks of pancake coils made of closely packed thin conductors, such as ReBCO coated conductors [10].…”

Section: Introductionmentioning

confidence: 99%

“…An important step forward for the modelling of single pancake coils has been the continuous approximation, introduced in [11] for stacks of tapes, further developped for Finite Element Methods in [12] and applied to circular coils in [10].…”

Section: Introductionmentioning

confidence: 99%

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Modeling of AC Loss in Coils Made of Thin Tapes Under DC Bias Current

Pardo¹

2014

IEEE Trans. Appl. Supercond.

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Many applications, such as magnets and SMES, are usually charged and discharged under a bias DC current, which may increase the AC loss. For their design, it is necessary to understand and predict the AC loss. This article analises the AC loss in magnet-like coils under DC bias contribution super-imposed to the AC current. The analyses is based on a numerical model that takes the interaction between magnetization currents in all turns into account. The studied example is a stack of 32 pancake coils with 200 turns each made of thin tape, such as ReBCO coated conductor. We present the current density, the instantaneous power loss, and loss per cycle. We have found that the loss increases with the DC bias current. The instantaneous power loss is the largest in the initial rise of the the AC current. In following cycles, the power loss is higher in the current increase than in the decrease. The loss per cycle is the largest at the end pancakes. In conclusion, the highest cooling power should be supplied to the top and bottom pancakes and during current rise, specially the initial one. The presented model has a high potential to predict the AC loss in magnet-size coils, useful for their design.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Modeling of AC Loss in Coils Made of Thin Tapes Under DC Bias Current

Pardo¹

2014

IEEE Trans. Appl. Supercond.

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“…The sub-routine to calculate ∆A e and B e is also parallelized. The computing time can be further reduced by using the continuous approximation for densely packed pancake coils [9,12,17]. This results in a reduction of the effective number of turns per pancake, in our case from 400 real turns to 40 effective turns.…”

Section: Modelmentioning

confidence: 98%

Modeling of screening currents in coated conductor magnets containing up to 40000 turns

Pardo

2016

Supercond. Sci. Technol.

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Screening currents caused by varying magnetic fields degrade the homogeneity and stability of the magnetic fields created by REBCO coated conductor coils. They are responsible for the AC loss, which is also important for other power applications containing windings. Since real magnets contain coils exceeding 10000 turns, accurate modeling tools for this number of turns are necessary for magnet design. This article presents a fast numerical method to model coils with no loss of accuracy. We model a 10400-turn coil for its real geometry and coils of up to 40000 turns with the continuous approximation, which we checked that introduces negligible errors. The screening currents, the Screening Current Induced Field (SCIF) and the AC loss is analyzed in detail. The SCIF is maximum at the remnant state with a considerably large value and decreases substantially after one day of relaxation. The instantaneous AC loss for an anisotropic magnetic-field dependent Jc is qualitatively different than for a constant Jc, although the loss per cycle is similar. Saturation of the magnetization currents at the end pancakes causes that the maximum AC loss at the first ramp increases with Jc. The presented modeling tool can accurately calculate the SCIF and AC loss in practical computing times for coils with any number of turns used in real windings, enabling parameter optimization.

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“…The finite element modeling (FEM) is put forward to calculate the actual current distributions [6], [10], [20], [21], but it is not for the coil with a large number of turns. To calculate the current distribution in the coil with large number of turns, Naoyuki et al [2], Enric [7], and Min et al [10] presented different numerical methods, such as FEM, and minimum magnetic energy variation (MMEV) method. However, the computation still needs a long time for the coil with thousands of turns.…”

Section: Introductionmentioning

confidence: 99%

Analysis of Current Distribution in Bi-2223/Ag Insert Pancake Coil

Wang

et al. 2015

IEEE Trans. Appl. Supercond.

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A Bi-2223/Ag insert was fabricated to assemble a high field superconducting magnet. The insert consists of 17 double pancakes, with turn to turn and layer to layer insulations. To get the current distribution in each turn of the pancake coil, a numerical method of magnetization in a thin film derived from E.Zeldov was employed. To improve the calculation accuracy, we add the I C data tested from the experiments into the code directly. In the calculation, we take several different cases into account, such as High Field-Low Current (HFLC) case, Low Field-High Current (LFHC) case, which will have an effect on the current distributions. The overall process is divided into three sections: Firstly, we calculate the nonuniform but symmetrical transport current distributions through the transport current model. Secondly, the non-uniform and asymmetrical transport current distributions is recalculated through the magnetic field and transport current model. Thirdly, the screening current distributions are calculated after the coil is discharged.

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Calculation of AC loss in coated conductor coils with a large number of turns

Cited by 42 publications

References 36 publications

Modeling of AC Loss in Coils Made of Thin Tapes Under DC Bias Current

Modeling of AC Loss in Coils Made of Thin Tapes Under DC Bias Current

Modeling of screening currents in coated conductor magnets containing up to 40000 turns

Analysis of Current Distribution in Bi-2223/Ag Insert Pancake Coil

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