Numerical study on AC loss reduction of stacked HTS tapes by optimal design of flux diverter

Liu, Guole; Zhang, Guomin; Jing, Liwei; Yu, Haizhou

doi:10.1088/1361-6668/aa9362

Cited by 31 publications

(16 citation statements)

References 25 publications

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“…The influence of flux diverters on the reduction of transport current loss has been verified in [237], and it is shown that the favored diverter material should possess both a low remanence and a high saturation field. Liu has studied the geometric dimension and location optimization of the magnetic flux diverter for a better loss reduction effect [238][239][240]. The results in [238] have shown that the flux diverter demonstrates an adverse consequence on the CC critical current, depending on the width, height of the diverter, and the gap between the diverter and the HTS coils.…”

Section: Flux Divertersmentioning

confidence: 99%

“…Liu has studied the geometric dimension and location optimization of the magnetic flux diverter for a better loss reduction effect [238][239][240]. The results in [238] have shown that the flux diverter demonstrates an adverse consequence on the CC critical current, depending on the width, height of the diverter, and the gap between the diverter and the HTS coils. In [239], the authors show that, besides the positions of flux diverters, their loss reduction effect is also related to the load ratio between the transport current and critical current, e.g., the use of flux diverters in the middle and end positions of the double pancake coil can reduce the AC loss by 70%.…”

Section: Flux Divertersmentioning

confidence: 99%

See 1 more Smart Citation

Alternating Current Loss of Superconductors Applied to Superconducting Electrical Machines

Zhang¹,

Wen²,

Grilli

et al. 2021

Energies

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Superconductor technology has recently attracted increasing attention in power-generation- and electrical-propulsion-related domains, as it provides a solution to the limited power density seen by the core component, electrical machines. Superconducting machines, characterized by both high power density and high efficiency, can effectively reduce the size and mass compared to conventional machine designs. This opens the way to large-scale purely electrical applications, e.g., all-electrical aircrafts. The alternating current (AC) loss of superconductors caused by time-varying transport currents or magnetic fields (or both) has impaired the efficiency and reliability of superconducting machines, bringing severe challenges to the cryogenic systems, too. Although much research has been conducted in terms of the qualitative and quantitative analysis of AC loss and its reduction methods, AC loss remains a crucial problem for the design of highly efficient superconducting machines, especially for those operating at high speeds for future aviation. Given that a critical review on the research advancement regarding the AC loss of superconductors has not been reported during the last dozen years, especially combined with electrical machines, this paper aims to clarify its research status and provide a useful reference for researchers working on superconducting machines. The adopted superconducting materials, analytical formulae, modelling methods, measurement approaches, as well as reduction techniques for AC loss of low-temperature superconductors (LTSs) and high-temperature superconductors (HTSs) in both low- and high-frequency fields have been systematically analyzed and summarized. Based on the authors’ previous research on the AC loss characteristics of HTS coated conductors (CCs), stacks, and coils at high frequencies, the challenges for the existing AC loss quantification methods have been elucidated, and multiple suggestions with respect to the AC loss reduction in superconducting machines have been put forward. This article systematically reviews the qualitative and quantitative analysis methods of AC loss as well as its reduction techniques in superconductors applied to electrical machines for the first time. It is believed to help deepen the understanding of AC loss and deliver a helpful guideline for the future development of superconducting machines and applied superconductivity.

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Section: Flux Divertersmentioning

confidence: 99%

Section: Flux Divertersmentioning

confidence: 99%

Alternating Current Loss of Superconductors Applied to Superconducting Electrical Machines

Zhang¹,

Wen²,

Grilli

et al. 2021

Energies

View full text Add to dashboard Cite

show abstract

“…The use of ferromagnetic flux diverters is another effective method to reduce AC loss in HTS coil windings comparable to using low loss conductors. Flux diverters are used to reshape the flux distribution around coil windings to reduce AC loss or increase critical current of DC coil windings [17][18][19][20][21][22][23][24][25][26][27][28]. Previous studies have proven that magnetic flux diverters (MFDs) can reduce AC loss in Bi-2223 coils [18,23,24].…”

Section: Introductionmentioning

confidence: 99%

AC loss measurement and simulation in a REBCO coil assembly utilising low-loss magnetic flux diverters

You

Staines

Sidorov

et al. 2020

Supercond. Sci. Technol.

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AC loss in high temperature superconducting (HTS) coils affects the performance of HTS devices. Using magnetic flux diverters (MFDs) is an effective way to reduce AC loss in HTS coils. In this paper, measurement and finite element method simulation of AC loss results in a REBCO coil assembly comprising four double pancake coils with two molypermalloy-powder MFDs are presented. Both experimental and numerical results show that MFDs can significantly reduce the AC loss in the REBCO coil assembly while generating negligible loss in themselves. Further, the influence of the distance between the coil assembly and the diverters on AC loss reduction is explored. Compared with the AC loss data in the coil assembly without MFDs, over 80% AC loss reduction is achieved when the distance between the coil assembly and the diverters is at its minimum value, 2 mm. The simulation results reveal that the AC loss reduction in the coil assembly is mainly due to the reduction of the radial (perpendicular) magnetic field component to the surface of REBCO wires in the end windings of the coil assembly.

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“…Althgough, uncoupled stacks (and coils) and fully coupled stacks have been well studied by many researchers before, the case of an intermediate finite resistance ("partial coupling") has not been previously studied for stacks of tapes. Previous studes focused on ac loss under perpendicular magnetic field [19][20][21][22][23][24][25][26][27], ac loss under transport current [28][29][30][31][32], ac loss with consideration of ferromagnetic material [33][34][35][36], dynamic resistance under various applied field [37][38][39][40], magnetization and decay of trapped magnetic field [41][42][43][44][45][46][47][48], multifilamentary calculations [19,49], among other topics. Thanks to the presented numerical 2D MEMEP model, this article systematically studies and discusses the amplitude-dependence, frequency-dependence, and resistance-dependence of coupling loss under parallel magnetic field.…”

Section: Introductionmentioning

confidence: 99%

Coupling loss at the end connections of REBCO stacks: 2D modelling and measurement

Li,

Pardo,

Kovac

2020

Preprint

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In high power density superconducting motors, superconducting tapes are usually stacked and connected together at terminals to improve the current capacity. When a parallel sinusoidal magnetic field is applied on this partially coupled stack, the coupling current is induced and causes additional coupling loss. Usually 3D modeling is needed to calculate the coupling loss but it takes too much computing resource and time. In this paper, a numerical 2D modeling by minimum electromagnetic entropy production (MEMEP) method is developed to speed up the calculation. The presented MEMEP model shows good accuracy and the capability to take the realistic resistance between tapes into account for coupling loss calculation with a high number of mesh element, which agrees to measurements.Thanks to the model, a systemic study of coupling loss on amplitude-dependence, frequency-dependence, resistance-dependence, and length-dependence, is presented and discussed. The results reveal the features of coupling loss which is very helpful devices with multi-tape conductors, such as the stator or rotor windings of motors.

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Numerical study on AC loss reduction of stacked HTS tapes by optimal design of flux diverter

Cited by 31 publications

References 25 publications

Alternating Current Loss of Superconductors Applied to Superconducting Electrical Machines

Alternating Current Loss of Superconductors Applied to Superconducting Electrical Machines

AC loss measurement and simulation in a REBCO coil assembly utilising low-loss magnetic flux diverters

Coupling loss at the end connections of REBCO stacks: 2D modelling and measurement

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