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Dissertations / Theses on the topic 'Breakdown (Electricity)'
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1
Hanby, David William. "Breakdown characteristics of nonuniform electric fields in crossflows /." This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-12172008-063445/.
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2
Hamby, David William. "Breakdown characteristics of nonuniform electric fields in crossflows." Thesis, Virginia Tech, 1993. http://hdl.handle.net/10919/46298.
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<p>An experimental evaluation of the breakdown characteristics of the nonunifonn
electric fields established between two spheres and between two points in a crossflow was
conducted and the results were then compared to the breakdown characteristics in
quiescent air. The aluminum spheres used in this investigation ranged in diameter from
0.635 em to 2.54 em. The points had a radius of curvature of 0.5 mm. The velocities
of the crossflow ranged from 23 mls to 58 mls and the gap distances ranged from 0.5 cm
to 2.0 cm. Photography was used to determine the effect of the crossflow on the
luminous spark for all electrodes. The sparking voltages in the crossflow were a function
of the crossflow velocity, electrode size and gap distance. It was concluded that the most
significant increase of sparking voltages in a crossflow, as compared to the same
configuration in quiescent air, was for the point-point gap at a distance of 2.0 cm for a
58 mls crossflow. As the electrodes were increased in size, the effect of a given
crossflow decreased. For the 2.54 cm spheres with a 58 mls crossflow, there was actually
a decrease in the sparking voltage as compared to its counterpart in quiescent air. The
photographs showed a significant deflection of the spark in the direction of the crossflow
for the point-point gap, but no significant deflection was detected for the other electrode
geometries.<br>Master of Science
3
Tan, Leong Hin 1957. "Two-dimensional device simulation of junction termination structures for determination of breakdown behavior." Thesis, The University of Arizona, 1989. http://hdl.handle.net/10150/277067.
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In this work, we have investigated numerical techniques to determine the breakdown behavior of complex semiconductor devices using two-dimensional simulation. In particular, we have augmented the device simulator SEPSIP with a capability for handling single and multiple floating field rings, and for handling devices with slanted edges. We have furthermore improved the grid width selection algorithm in SEPSIP. A capability for plotting equi-field contours was added to the code. Finally, all system dependencies were removed from the SEPSIP code, and a new version of SEPSIP (Version 2.0) was generated which can be executed on any PC/XT, PC/AT, or PC/386 compatible computer. This eliminates the need for transfering files back and forth between the PC, which had formerly been used as an I/O processor, and the VAX, which was used for numerically intensive computations. It also makes the code more accessible to scientists and engineers who are working in this important research area.
4
Watts, Frank. "The effect of electrical potential on mass transfer in liquid-liquid extraction." Diss., Georgia Institute of Technology, 1990. http://hdl.handle.net/1853/10283.
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5
Dickinson, Laurie Alan. "Studies of magneto-tunneling into donor states and of the breakdown of the quantum Hall effect." Thesis, University of Nottingham, 2004. http://eprints.nottingham.ac.uk/14393/.
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This thesis describes an experimental investigation and analysis of two topical problems in condensed matter physics: 1.) the effect of a magnetic field on quantum states of an electron bound to a shallow donor impurity in a quantum well heterostructure and 2.) the breakdown of the quasi-dissipationless state of the integer quantum Hall effect. Two introductory chapters describe important material parameters and the experimental equipment and techniques used. Magneto-tunneling spectroscopy (MTS) is used to probe the spatial form of the eigenfunction of electrons bound in the ground state of a shallow Si-donor impurities in a GaAs/(A1Ga)As quantum well. An in-plane magnetic field, B[subscript] |, acts to tune the k-vector of the tunnelling electron through the effect of the Lorentz force. The variation with B [subscript] | of the tunnel current through the donor ground state provides a map of the Fourier transform, |ψ(k)| [superscript]2, of the probability density of the ground state donor wavefunction in real space. By applying a strong magnetic field component, B [subscript] ||, parallel to the direction of tunnel current, it is possible to magneto-compress the donor function in real space. The magneto-compression is investigated using MTS and the data are analysed in terms of a simple model, which is critically discussed. The breakdown of the integer quantum Hall effect is investigated by measuring the variation of the voltage drop Vxx along the direction of current flow for a range of currents and magnetic fields and for a number of sample geometries including Hall bars with narrow channels. The data are discussed in terms of two complementary models of breakdown: the bootstrap electron heating model and magneto-exciton formation at a charged impurity. Evidence is found for both types of breakdown depending on the type of sample used and on experimental parameters. For samples with constrictions, it is found that in the breakdown region the value of Vxx measured across a pair of contacts on one side of the Hall bar can differ substantially from that measured on the other side. A model based on magneto-exciton formation at impurities is proposed to explain this unexpected effect. The thesis concludes with a brief summary and suggestions for future work.
6
Cheung, Chi Wai. "Application of fracture mechanics to dielectric breakdown in air, silicone oil and silicone rubber /." View abstract or full-text, 2009. http://library.ust.hk/cgi/db/thesis.pl?MECH%202009%20CHEUNG.
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Saed, Mohammed Ali. "Dielectric characterization using a Wideband Dielectric Filled Cavity (WDFC)." Diss., Virginia Polytechnic Institute and State University, 1987. http://hdl.handle.net/10919/52317.
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This dissertation summarizes the research performed towards the development, analysis, and testing of two new sample configurations used for characterizing dielectric materials over a wide band of frequencies. In the two configurations, a cylindrical cavity completely filled with a sample of the dielectric material of interest is used. The two configurations are the following:
1. The cylindrical cavity is adapted to the end of a transmission line and the reflection coefficient is measured. The complex permittivity of the dielectric sample is then derived from the measured reflection coefficient information.
2. The cylindrical cavity is placed between two transmission lines. The complex permittivity of the dielectric material can be computed from either the measured reflection coefficient or the measured transmission coefficient.
The full field analysis of these configurations is carried out and the solution is obtained using the method of moments. Computer simulation experiments are performed to test the sensitivity of these techniques and predict their performance. Actual experiments on some dielectric materials with known dielectric properties are performed for verification. The first configuration is also used to characterize two thick film dielectric materials.
These configurations proved to provide solutions to the many problems with the conventional configurations found in the literature.<br>Ph. D.
8
Liu, Xin. "Partial discharge detection and analysis in low pressure environments." Columbus, Ohio : Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1155573657.
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9
Bashir, Muhammad Muqarrab. "Modeling reliability in copper/low-k interconnects and variability in cmos." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/41092.
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The impact of physical design characteristics on backend dielectric reliability was modeled. The impact of different interconnect geometries on backend low-k time dependent dielectric breakdown was reported and modeled. Physical design parameters that are crucial to backend dielectric reliability were identified. A methodology was proposed for determining chip reliability but combining the insights gathered by modeling the impact of physical design on backend dielectric breakdown.
A methodology to model variation in device parameters and characteristics was proposed. New methods of electrical and physical parameter extraction were proposed. Models that consider systematic and random source of variation in electrical and physical parameters of CMOS devices were proposed, to aid in circuit design and timing analysis.
10
Tirino, Louis. "Transport Properties of Wide Band Gap Semiconductors." Diss., Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/5210.
Full textAbstract:
Transport Properties of Wide Band Gap Semiconductors
Louis Tirino III
155 pages
Directed by Dr. Kevin F. Brennan
The objective of this research has been the study of the transport properties and breakdown characteristics of wide band gap semiconductor materials and their implications on device performance. Though the wide band gap semiconductors have great potential for a host of device applications, many gaps remain in the collective understanding about their properties, frustrating the evaluation of devices made from these materials.
The model chosen for this study is based on semiclassical transport theory as described by the Boltzmann Transport Equation. The calculations are performed using an ensemble Monte Carlo simulation method. The simulator includes realistic, numerical energy band structures derived from an empirical pseudo-potential method. The carrier-phonon scattering rates and impact ionization transition rates are numerically evaluated from the electronic band structure. Several materials systems are discussed and compared. The temperature-dependent, high-field transport properties of electrons in gallium arsenide, zincblende gallium nitride, and cubic-phase silicon carbide are compared.
Since hole transport is important in certain devices, the simulator is designed to simulate electrons and holes simultaneously. The bipolar simulator is demonstrated in the study of the multiplication region of gallium nitride avalanche photodiodes.
11
Ribeiro, Júnior Sebastião. "Desenvolvimento de metodologia para análise de arborescências em materiais dielétricos por contraste de fase de raios X." Universidade Tecnológica Federal do Paraná, 2013. http://repositorio.utfpr.edu.br/jspui/handle/1/690.
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A ocorrência de arborescências em água (water tree) ou elétrica (electrical tree) é apontada como o principal fenômeno de degradação em isolações sólidas de cabos de distribuição de energia elétrica. A evolução destas arborescências pode levar a camada de isolação à ruptura dielétrica e, como conseqüência, à falha destes equipamentos, com a interrupção do fornecimento de energia elétrica. O entendimento deste fenômeno é necessário para desenvolver métodos de análise e prevenção da ruptura de materiais isolantes. Este trabalho mostra a aplicação da técnica contraste de fase por raios X como metodologia para o estudo das arborescências formadas em materiais isolantes de borracha de propileno etileno (EPR) e polietileno reticulado (XLPE).<br>The water tree or electrical tree occurrence is identified as the main phenomena in the degradation in solid isolations of the electric energy distribution cables. The water tree evolution can lead to dielectric breakdown of the isolation layer and, consequently, to the failure this equipment and the interruption of the electric energy supply. The understanding this phenomenon is necessary for the development analysis methods and to prevent collapse in the polymeric insulation. This work demonstrates the application of X-ray phase contrast technique as a methodology for the study of the water tree and electrical tree in Ethylene propylene rubber (EPR) and crosslinked polyethylene (XLPE).
12
Ehlers, Richard. "Determining the switching impulse breakdown voltage over large air gaps with an application to tower-conductor window configurations." Thesis, 1998. http://hdl.handle.net/10539/22712.
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A dissertation submitted to the Faculty of Engineering,
University of the Witwatersrand, in fulfilment of the
requirements for the degree of Master of Sclenice in
Engineering
February 20th, 1998<br>All available model used to determine the 50% breakdown voltage for rod-type ami
conductor-type gaps subject to switching is impulse wave forms has been applied to a tower-conductor
window gap configurution. The results for rod-plane, conductor-piane and tower-conductor
window gaps have all been compared and correspond well with practical data. III
order to app(v the model, a charge simulation technique has been adopted ill conjunction
with the 'Coulomb 3D' charge simulation package. Additional tests have been performed
where parameters of'the charge simulation method am! the electrode geometl:p hare been
adjusted and consequent conclusions made. Recommendations for further application of tile
model have been suggested.<br>MT2017
13
Bhutt, Sanjeev. "An investigation into methods of modelling positive inhomogeneous-field breakdown and discharge process in SF6 with emphasis on the corona stabilisation phenomenon." Thesis, 2016. http://hdl.handle.net/10539/20685.
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dissertatic,11 submitted to the Faculty of Engineering, University of the
Witwatersrand, Johannesburg, in fulfillment of the requirements for the degree of
Master of Science in Engineering,
I.:
Johannesburg, 1998<br>Corona stabilisation is not a well understood phenomenon, consequently a rigorous
theoretical description of how the merhanism operates does not exist. Furthermore,
postulates on the prcJ'.tse physical processes that occur during corona stabilised
breakdown are varied and conflicting. 1t was thus essential to develop a qualitative
theory of how the mechanism operates around which a quantitative model could be
constructed. To this aim, a detailed analysis of available modelling methods and
empirical data from published works was carried out. This analysis together with
additional finite elements modelling done as part of this work, leads to a proposed
qualitative model which serves as a basis for a quantitative model developed to
simulate corona stabilized breakdown from a fixed panicle defect. There is a
favorable comparison between the predictions of the model and published
measurements, thus imbuing optimism in the proposed method. The problem of
measuring t: .;true charge deployed in a discharge is discussed and an experiment is
designed to circumvent this problem.
14
Misra, Mayank. "Molecular Modeling for Rational Design of Polymer Dielectrics." Thesis, 2017. https://doi.org/10.7916/D86M3DSH.
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The state-of-the-art in high voltage and high energy density capacitors is dominated by biaxially oriented polypropylene (BOPP), a linear dielectric with electronic polarizability but low dielectric constant (2.2). BOPP provides an energy density of 5 J/cm3 at the breakdown, which occurs at 720 MV/m for films 10 micrometer thick. While there are many approaches to increase the energy, they either offer solutions to specific applications or suffer from fundamental limitations. The principal focus of the dissertation will be centered on rational design for the development of such materials. We study all three verticals of dielectric properties, namely: dielectric permittivity; dielectric loss; and breakdown strength. We then use the information obtained to design a copolymer with enhanced dielectric properties. We start by using simulations and experiments to delineate the mechanism by which the addition of a small number of polar --OH groups to a nonpolar polymer increases the static relative permittivity (or dielectric constant) by a factor of 2. However, the dielectric loss in the frequency regime of interest to power electronics is less than 1%. We observe that a small amount of adsorbed water plays a critical role in this attenuated loss. Further, we study the effect of other polar pendant groups on dielectric properties of polyethylene. By systematically comparing the static relative permittivity of crystalline and semi-crystalline samples we find amorphous phase as the dominant player in these types of material. The constraints provided by the surrounding chains significantly impede dipolar relaxations in the crystalline regions, whereas amorphous chains must sample all configurations to attain their fully isotropic spatial distributions. We also explore the use of the time--temperature superposition (tTS) principle for calculating the dielectric loss of the dielectric materials. This approach helps us explore time scales in simulations which were previously inaccessible using classical MD. We find that the tTS method performed well in determining dielectric losses in the system as long as unrelaxed components are not included in the calculation. This methodology, which provides us with a significantly faster and reliable pathway for calculation of dielectric loss, allows us to identify the role of polar sidegroups on the dielectric loss of common non-polar polymeric dielectrics. Further, we explore the dielectric breakdown mechanism in polymer dielectrics by introducing external electric fields in the materials. Conventionally the prediction of dielectric strength has focused on ground state energy calculation, thus restricting the analysis of the breakdown process to purely electronic in nature. While this provides reasonable predictions for low-temperature systems, we observe that electromechanical breakdown plays a crucial role in the high-temperature regimes. Our simulation results suggest that fracture mechanics drive electromechanical breakdown, which dominates over electronic breakdown at relevant operating temperatures. Finally, we utilized these fundamental insights into dielectric properties for designing copolymer with enhanced dielectric properties.
15
Thomas, Benny. "Investigations Into Internal Partial Discharge Ageing And Breakdown Of Thin Polypropylene Films." Thesis, 1997. http://etd.iisc.ernet.in/handle/2005/1822.
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16
Gora, Tatenda. "Investigating the effects of altitude (air density) on the HVDC breakdown voltage of small rod-plane air gaps." Thesis, 2016. http://hdl.handle.net/10539/21106.
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A dissertation submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science in Engineering, 2016<br>The validity of the atmospheric correction method presented in the IEC 60060-1 (2010)
standard is analysed and evaluated by means of theoretical and laboratory work. In
order to understand the problem, the evolution of the atmospheric correction methods,
from as early as 1914, has been presented. A procedure (Calva prediction method) for
predicting the direct current (DC) breakdown voltage for an air gap at any altitude
was discovered and was also analysed along with the IEC 60060-1 (2010). A critique of
some of the atmospheric correction methods commonly used standards was also done.
Experiments were carried out at altitudes of 1 740 m (Wits University), 130 m (UKZN
HVDC centre) and at less than 2 m above sea level (Scottburgh beach, Clansthal). More
tests were conducted using a pressure vessel where high altitude relative air density was
simulated. All tests were conducted on rod-plane air gaps using a 15 mm diameter
at tip rod. Test results from Scottburgh beach were used as the standard breakdown
voltages of the air gaps tested since the environmental conditions were the closest to the
conventional standard conditions (stp). The test results obtained were compared with
predictions using the Calva method in order to validate the method. The test results
were also corrected according to IEC 60060-1 (2010) and compared to the standard
breakdown voltages obtained at Scottburgh beach. It was shown that the IEC 60060-1
(2010) is quite suitable for atmospheric correction for data obtained at low altitudes
(about 130 m). When applied to high altitude (1 740 m) data, the correction method
is accurate and suitable for very small air gaps less than 0.1 m. As the air gap length
increased, the corrected results began to deviate from the expected standard voltage.
The same trend was shown with the corrected results from the pressure chamber tests.
The prediction method by Calva was accurate when compared to the experimental data
from the high altitude and low altitude test results. When compared to the data from
the pressure chamber, the prediction method had a linear error factor which was di erent
for each gap length. It was concluded that the IEC 60060-1 (2010) is not only unsuitable
for atmospheric correction for data at relative air densities below 0.8, but also that the
correction method is prone to an increase in error as the air gap length increases when
the relative air density is higher than 0.8. The Calva prediction method was found
to be suitable to use after additional factors are added when applied to high altitude
conditions.<br>GR2016
17
Kim, Young-Hee Lee Jack Chung-Yeung. "Interface engineering and reliability characteristics of HfO₂ with poly Si gate and dual metal (Ru-Ta alloy, Ru) gate electrode for beyond 65nm technology." 2004. http://repositories.lib.utexas.edu/bitstream/handle/2152/2044/kimy042.pdf.
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Kim, Young-Hee. "Interface engineering and reliability characteristics of HfO₂ with poly Si gate and dual metal (Ru-Ta alloy, Ru) gate electrode for beyond 65nm technology." Thesis, 2004. http://hdl.handle.net/2152/2044.
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Bokoro, Pitshou Ntambu. "Degradation analysis of metal oxide varistors under harmonic distortion conditions." Thesis, 2016. http://hdl.handle.net/10539/21153.
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A thesis submitted in ful lment of the requirements
for the degree Doctor of Philosophy
in Electrical Engineering
May 2016<br>Modern electrical networks provide an opportunity for inevitable interaction between
metal oxide arresters and power system harmonics. Therefore, these arrester devices
are continuously exposed to the combined e ect of distorted system voltage and envi-
ronmental thermal stresses. Recent studies supported by eld experiments have shown
signi cant rise in the leakage current through these surge arrester devices when exposed
to ac voltage with harmonics. However, the major shortcoming in the current knowledge
and applications of varistor arresters resides on the reliability and the electrical stabil-
ity of these overvoltage protection units, when subjected to long-term and continuous
distorted ac voltage and thermal stresses from the environment.
Commercially-sourced ZnO arresters of similar size and electrical properties are tested
using standard ac accelerated degradation procedure or electro-thermal ageing test. The times
to degradation, the coe cient of non-linearity, the reference voltages, as well as the
clamping voltage measured are used to analyse the reliability and the electrical stability
of the metal oxide-based arrester samples. The resistive component of the leakage current
is extracted from the measured total leakage current. The three-parameter Weibull
probability model is invoked in order to analyze the degradation phenomenon.<br>MT2016