Experiment Setup for Calorimetric Measurements of Losses in HTS Coils Due to AC Current and External Magnetic Fields

Murphy, John P.; Mullins, M. J.; Barnes, Paul N.; Haugan, Timothy J.; Levin, Gilbert V.; Majoroš, M.; Sumption, M.D.; Collings, E. W.; Polák, M.; Mozola, P.

doi:10.1109/tasc.2013.2237939

Cited by 25 publications

(11 citation statements)

References 18 publications

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“…The experimental results are consistent with the model calculations, though there exists a discrepancy between the modelling results and the electric-method-based experimental data at large currents [191]. Figure 13a shows a calorimetric system to measure the total AC loss of superconducting tapes or coils based on the boil-off of liquid nitrogen, proposed by Murphy et al [192]. With the help of the proposed calorimeter system, a permanent magnet rotor has been designed to simulate the electromagnetic environment of an electrical machine, and the AC loss of one armature coil carrying AC current exposed to rotating fields has been measured, as shown in Figure 13b.…”

Section: Measurement Of the Cryogen Evaporationsupporting

confidence: 70%

“…The calorimetric system can measure low losses from a few milliwatts to several hundred milliwatts [192].…”

Section: Measurement Of the Cryogen Evaporationmentioning

confidence: 99%

“…Figure 13. Diagram of a LN2 boil-off calorimeter system for measuring AC losses of coils, adapted from [192]: (a) AC transport current loss measurement of an HTS coi measurement of an armature coil in the environment of an electrical machine.…”

Section: Measurement Of the Cryogen Evaporationmentioning

confidence: 99%

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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: Measurement Of the Cryogen Evaporationsupporting

confidence: 70%

“…The calorimetric system can measure low losses from a few milliwatts to several hundred milliwatts [192].…”

Section: Measurement Of the Cryogen Evaporationmentioning

confidence: 99%

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Alternating Current Loss of Superconductors Applied to Superconducting Electrical Machines

Zhang¹,

Wen²,

Grilli

et al. 2021

Energies

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“…Previous stability studies have already been performed on ReBCO tapes, cables, and coils [6,[12][13][14][15][16][17][18][19]. The large temperature margins of HTS conductors will likely prevent epoxy cracking, friction from sudden mechanical motion, and flux jumps from initiating a quench [6].…”

Section: Introductionmentioning

confidence: 99%

Quench and stability of Roebel cables at 77 K and self-field: Minimum quench power, cold end cooling, and cable cooling efficiency

et al. 2018

Self Cite

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A 9-tape, 14 mm wide ReBCO Roebel cable was soldered onto a U-shaped holder. The critical current, Ic, was measured at 77 K and self-field. The cryostability of the cable was studied in response to the application of local pulses of 1 to 14 W at several values of i = I/Ic. A detailed analysis of the cable's cryostability was presented. With a Stekly parameter α = G/Q « 1 and a heat generation margin of ~190 kW/m 2 the present ReBCO cable was shown to be ultra cryostable with respect to internally generated transport-current overload. However, the cable was much less stable against externally and locally applied disturbances because of the tendency to initiate local film boiling. A locally applied 10 W led to a prediction of a film-boiling-cooled zone with a temperature of 181 K. However, when cold-end cooling was considered, the predicted hot spot temperature decreased to 87-115 K depending on the surface-cooling efficiency. Predictions were compared to experiment extracting a cooling efficiency parameter representing the penetration of the cryogen into the cable. Experiment showed the generation of time stable normal zones which were a function of disturbance power. This led to the description of the cable stability in terms of minimum quench power; the results are presented in stability diagrams.

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“…Measurement of AC losses is then an important topic of research in superconductivity. AC losses can be measured using two kinds of methods: electromagnetic [3]- [6] and calorimetric [7], [8]. In this work an electromagnetic method using a lock-in amplifier is addressed.…”

Section: Introductionmentioning

confidence: 99%

Contactless Loop Method for Measurement of AC Losses in HTS Coils

Amaro¹,

Šouc

Pina³

et al. 2015

IEEE Trans. Appl. Supercond.

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Measurements of ac losses in high-temperature superconducting (HTS) coils are of utmost importance for power applications because these are one of the most limiting factors in superconducting devices. There are two possible ways to measure such losses: calorimetric and electromagnetic methods. An electromagnetic method using a contactless loop is reported in this paper. To verify the applicability of such method in mediumto large-sized coils, two different contactless loops were designed and built, and results are compared with those obtained from measurements made with different configurations of voltage taps. All tests were performed at 77 K, using a superconducting coil with a variable number of turns (up to a maximum of 128) wound from BSCCO tape. Currents ranging from zero to the critical value were applied, at frequencies from 72 to 1152 Hz.

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Experiment Setup for Calorimetric Measurements of Losses in HTS Coils Due to AC Current and External Magnetic Fields

Cited by 25 publications

References 18 publications

Alternating Current Loss of Superconductors Applied to Superconducting Electrical Machines

Alternating Current Loss of Superconductors Applied to Superconducting Electrical Machines

Quench and stability of Roebel cables at 77 K and self-field: Minimum quench power, cold end cooling, and cable cooling efficiency

Contactless Loop Method for Measurement of AC Losses in HTS Coils

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Experiment Setup for Calorimetric Measurements of Losses in HTS Coils Due to AC Current and External Magnetic Fields

Cited by 25 publications

References 18 publications

Alternating Current Loss of Superconductors Applied to Superconducting Electrical Machines

Alternating Current Loss of Superconductors Applied to Superconducting Electrical Machines

Quench and stability of Roebel cables at 77 K and self-field: Minimum quench power, cold end cooling, and cable cooling efficiency

Contactless Loop Method for Measurement of AC Losses in HTS Coils

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Quench and stability of Roebel cables at 77 K and self-field: Minimum quench power, cold end cooling, and cable cooling efficiency