A Study on a Single-Phase HTS Transformer with a Cylindrical Central Iron Core

During the past decade, a number of high temperature superconducting (HTS) transformer prototypes have been designed, and the majority of them are full-core transformers and air-core transformers. However, in this study, we proposed a new type of HTS transformer, where the iron core is different in that the limbs and connecting yokes are absent. To investigate the performance of this type of HTS transformer, we design and fabricate a single-phase HTS partial core transformer prototype using the secondary generation (2G) HTS GdBCO wires. The iron core is at room temperature, and the windings are immersed in liquid Nitrogen. The structures of primary and secondary windings are three layers connected in series and nine double pancakes connected in parallel, respectively. Fundamental characteristics are obtained by standard short-circuit, no-load and load tests in liquid Nitrogen temperature of 77 K. In addition, an equivalent circuit of the HTS transformer is proposed to analyze the characteristic of the transformer. The calculated values based on the equivalent circuit are consistent with that of experiment. The detailed results about the design of the HTS partial-core transformer, the experiment, and the equivalent circuit are presented and discussed in this study.

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Estimation of Equivalent Circuit Parameters of Single-Phase Transformer by Using Chaotic Optimization Approach

Energies ◽

10.3390/en12091697 ◽

2019 ◽

Vol 12 (9) ◽

pp. 1697 ◽

Cited By ~ 6

Author(s):

Martin Ćalasan ◽

Danilo Mujičić ◽

Vesna Rubežić ◽

Milovan Radulović

Keyword(s):

Parameter Estimation ◽

Equivalent Circuit ◽

Single Phase ◽

Classical Method ◽

Short Circuit ◽

Average Error ◽

Optimization Approach ◽

Power Load ◽

Equivalent Circuit Parameters ◽

Output Characteristics

This paper deals with parameter estimation of single-phase transformer equivalent circuit by using Chaotic Optimization Approach (COA). Unknown transformer equivalent circuit parameters need to be accurately estimated for the best possible matching between the measured and the estimated transformer output characteristics (for example, output power—load resistance characteristic). Unlike literature approaches which apply different estimation techniques and are based either on the nameplate data or the load data obtained from experiments, in this paper the use of COA is evaluated on both types of input data. For two single-phase transformers, different with respect to machine power and voltage levels, the COA-based parameter estimation is compared to various literature techniques as well as to classical method based on open-circuit and short-circuit tests. The results show that COA outperforms other approaches in terms of average error between the measured and the estimated values of the primary current, secondary current and secondary voltage at full load, or between the measured and the estimated output characteristics. The effectiveness of COA is additionally confirmed through its application on laboratory 2kVA, 220 V/110 V, 50 Hz single-phase transformer.

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Augmented Short-Circuit Test for the Measurement of Transformer Equivalent-Circuit Parameters with Large Series Branch Impedances

International Journal of Electrical Engineering Education ◽

10.7227/ijeee.47.1.8 ◽

2010 ◽

Vol 47 (1) ◽

pp. 86-93

Author(s):

Saurabh Kumar Mukerji ◽

Moleykutty George

Keyword(s):

Equivalent Circuit ◽

High Voltage ◽

Single Phase ◽

Short Circuit ◽

Large Series ◽

Test Results ◽

Voltage Supply ◽

Short Circuit Test ◽

Equivalent Circuit Parameters

An augmented short-circuit test is described for the determination of equivalent-circuit parameters of single-phase transformers with large series-branch impedances. This test may be conducted at rated currents with the transformer connected to a reduced voltage supply. Thus harmonics in current and voltage waves are negligible. This test is therefore free from harmonics-associated errors. Based on test results, phasor equations are found which give formulae for the equivalent-circuit parameters with series-branch impedance split into low- and high-voltage components.

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Chemically disordered Ni3Al synthesized by high vacuum evaporation

Journal of Materials Research ◽

10.1557/jmr.1991.2019 ◽

1991 ◽

Vol 6 (10) ◽

pp. 2019-2021 ◽

Cited By ~ 50

Author(s):

S.R. Harris ◽

D.H. Pearson ◽

C.M. Garland ◽

B. Fultz

Keyword(s):

Liquid Nitrogen ◽

Room Temperature ◽

Single Phase ◽

High Vacuum ◽

Liquid Nitrogen Temperature ◽

Vacuum Evaporation ◽

Scanning Calorimetry ◽

X Ray ◽

Transmission Electron ◽

Average Grain Size

Films of chemically disordered fcc Ni3Al were synthesized by the vacuum evaporation of Ni3Al onto room temperature and liquid nitrogen temperature substrates. X-ray diffractometry and transmission electron microscopy showed the material to be single phase with an average grain size of about 4 nm. The formation of the equilibrium L12 ordered phase occurred simultaneously with grain growth at temperatures above 350°C. Differential scanning calorimetry provided ordering enthalpies of 7 kJ/mole and 9 kJ/mole for material evaporated onto room temperature and liquid nitrogen temperature substrates, respectively.

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Measurements of Gas Entrainment in Evaporating Spray Jets

Volume 1 ◽

10.1115/ht-fed2004-56195 ◽

2004 ◽

Author(s):

Muhammad Mushahid Rafique Qureshi ◽

Tong Lee ◽

Qun Yu ◽

Chao Zhu

Keyword(s):

Liquid Nitrogen ◽

Oxygen Concentration ◽

Single Phase ◽

Similarity Criterion ◽

Air Entrainment ◽

Liquid Nitrogen Temperature ◽

Entrainment Rate ◽

Two Phase ◽

Evaporating Spray ◽

Spray Jets

The jet-induced entrainment can be significantly different for jets with evaporating sprays, compared to those of single-phase jets. The heat and mass transfer properties of a liquid jet could be dominate factors governing the nature of the jet. These factors are mainly associated with the amount of mass of the surrounding air induced into the jet. In this study, we have experimentally investigated the air entrainment by a liquid nitrogen spray jet as well as that by a cold nitrogen gas jet near the liquid nitrogen temperature. An oxygen concentration measurement system was used to determine the local oxygen concentration that is purely due to the jet entrainment while the spray jet velocity was determined using a Laser Doppler Velocimetry system Temperature profiles were also monitored using a mini-sized thermocouple on a traverse. Entrainment velocities as well as mass entrainment rate of surrounding air into the jet were calculated by integrating the product of concentration and velocity within the spray jet boundary. Our results indicate that the jet similarity criterion still holds for two-phase evaporating liquid spray jets for circular nozzles. Experimental results of the entrainment rate and similarity of the single-phase jets were quantitatively compared against those from the classical jet theories. It is found that the mass flow rate of air entrained is significantly increased for the two-phase evaporating spray jets as compared to single-phase jets. Effect of spray evaporation on the spray jet expansion rates is also evaluated by comparing the jet expansion of the single-phase jets and those of two-phase evaporating spray jets.

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Power Law Breakdown in the Creep in Single-Phase Metals

Metals ◽

10.3390/met9121345 ◽

2019 ◽

Vol 9 (12) ◽

pp. 1345 ◽

Cited By ~ 2

Author(s):

M.E. Kassner ◽

R. Ermagan

Keyword(s):

Power Law ◽

Single Phase ◽

Short Circuit ◽

Steady State Creep ◽

The Past ◽

Diffusion Paths ◽

Diffusion Rates ◽

Short Circuit Diffusion ◽

Very High ◽

Insight Into

New analysis provides insight into the basis of power-law breakdown (PLB) in the steady-state creep of metals and alloys. A variety of theories has been presented in the past but this new examination suggests that there is evidence that a dramatic supersaturation of vacancies leading to very high diffusion rates and enhanced dislocation climb is associated with the rate-controlling process for creep in PLB. The effect of vacancy supersaturation may be enhanced by dislocation short circuit diffusion paths at lower temperatures due to the dramatic increase in dislocation density.

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Electron Probe Microanalysis of Frozen Hydrated Kidneys, Isolated Cells, and Cultured Cells

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100054595 ◽

1982 ◽

Vol 40 ◽

pp. 402-403 ◽

Cited By ~ 1

Author(s):

Claude Lechene

Keyword(s):

Liquid Nitrogen ◽

Electron Probe Microanalysis ◽

Electron Probe ◽

Cultured Cells ◽

Liquid Nitrogen Temperature ◽

Elemental Content ◽

Isolated Cells ◽

Renal Tubular Cells ◽

Diamond Saw ◽

Saw Blade

Electron probe microanalysis of frozen hydrated kidneysThe goal of the method is to measure on the same preparation the chemical elemental content of the renal luminal tubular fluid and of the surrounding renal tubular cells. The following method has been developed. Rat kidneys are quenched in solid nitrogen. They are trimmed under liquid nitrogen and mounted in a copper holder using a conductive medium. Under liquid nitrogen, a flat surface is exposed by sawing with a diamond saw blade at constant speed and constant pressure using a custom-built cryosaw. Transfer into the electron probe column (Cameca, MBX) is made using a simple transfer device maintaining the sample under liquid nitrogen in an interlock chamber mounted on the electron probe column. After the liquid nitrogen is evaporated by creating a vacuum, the sample is pushed into the special stage of the instrument. The sample is maintained at close to liquid nitrogen temperature by circulation of liquid nitrogen in the special stage.

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Field-Ion Microscopy of BCC Metals: A Study of Image Differences and Topographical Variations

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100071016 ◽

1973 ◽

Vol 31 ◽

pp. 114-115

Author(s):

O. T. Inal ◽

L. E. Murr

Keyword(s):

Liquid Nitrogen ◽

Liquid Nitrogen Temperature ◽

Surface Atom ◽

Image Brightness ◽

Field Ion Microscopy ◽

Topographic Features ◽

Bcc Metals ◽

Electron Orbital ◽

Ion Microscopy ◽

Field Ion Microscope

When sharp metal filaments of W, Fe, Nb or Ta are observed in the field-ion microscope (FIM), their appearance is differentiated primarily by variations in regional brightness. This regional brightness, particularly prominent at liquid nitrogen temperature has been attributed in the main to chemical specificity which manifests itself in a paricular array of surface-atom electron-orbital configurations.Recently, anomalous image brightness and streaks in both fcc and bee materials observed in the FIM have been shown to be the result of surface asperities and related topographic features which arise by the unsystematic etching of the emission-tip end forms.

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The Effects of Drying Techniques on Clay-Rich Soil Texture

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100052341 ◽

1974 ◽

Vol 32 ◽

pp. 466-467

Author(s):

T. G. Naymik

Keyword(s):

Critical Point ◽

Liquid Nitrogen ◽

Liquid Nitrogen Temperature ◽

Drying Methods ◽

Air Drying ◽

Freeze Dried ◽

Critical Point Drying ◽

Set Up ◽

The Relationship ◽

Quartz Grains

Three techniques were incorporated for drying clay-rich specimens: air-drying, freeze-drying and critical point drying. In air-drying, the specimens were set out for several days to dry or were placed in an oven (80°F) for several hours. The freeze-dried specimens were frozen by immersion in liquid nitrogen or in isopentane at near liquid nitrogen temperature and then were immediately placed in the freeze-dry vacuum chamber. The critical point specimens were molded in agar immediately after sampling. When the agar had set up the dehydration series, water-alcohol-amyl acetate-CO2 was carried out. The objectives were to compare the fabric plasmas (clays and precipitates), fabricskeletons (quartz grains) and the relationship between them for each drying technique. The three drying methods are not only applicable to the study of treated soils, but can be incorporated into all SEM clay soil studies.

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Water accumulation as a function of temperature on specimens in an electron microscope cold stage

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100142219 ◽

1986 ◽

Vol 44 ◽

pp. 114-115 ◽

Cited By ~ 2

Author(s):

M.K. Lamvik ◽

D.A. Kopf ◽

S.D. Davilla ◽

J.D. Robertson

Keyword(s):

Electron Microscope ◽

Mass Loss ◽

Liquid Helium ◽

Liquid Nitrogen ◽

Liquid Nitrogen Temperature ◽

Liquid Helium Temperature ◽

Helium Temperature ◽

Cold Stage ◽

Water Accumulation ◽

Better Than

Last year we reported1 that there is a striking reduction in the rate of mass loss when a specimen is observed at liquid helium temperature. It is important to determine whether liquid helium temperature is significantly better than liquid nitrogen temperature. This requires a good understanding of mass loss effects in cold stages around 100K.

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