Segui questo link per vedere altri tipi di pubblicazioni sul tema: Electric transformers.
Tesi sul tema "Electric transformers"
Cita una fonte nei formati APA, MLA, Chicago, Harvard e in molti altri stili
Vedi i top-50 saggi (tesi di laurea o di dottorato) per l'attività di ricerca sul tema "Electric transformers".
Accanto a ogni fonte nell'elenco di riferimenti c'è un pulsante "Aggiungi alla bibliografia". Premilo e genereremo automaticamente la citazione bibliografica dell'opera scelta nello stile citazionale di cui hai bisogno: APA, MLA, Harvard, Chicago, Vancouver ecc.
Puoi anche scaricare il testo completo della pubblicazione scientifica nel formato .pdf e leggere online l'abstract (il sommario) dell'opera se è presente nei metadati.
Vedi le tesi di molte aree scientifiche e compila una bibliografia corretta.
1
Siebrits, F. B. (Francois Bart). "Field implementation of a transient voltage measurement facility using HV current transformers". Thesis, Stellenbosch : Stellenbosch University, 2003. http://hdl.handle.net/10019.1/53426.
Testo completoAbstract (sommario):
Thesis (MScEng)--University of Stellenbosch, 2003.ENGLISH ABSTRACT: The bandwidth of standard HV measurement devices such as capacitive voltage transformers is too limited in order to measure wideband phenomena. This thesis is concerned with the investigation into a non- intrusive HV transient voltage measurement facility using standard substation HV current transformers (CI's) configured in a transconductance topology. The sensing, summation and integration of the CT capacitive earth currents are investigated. This thesis also reports on the development of a optically isolated link using optical fibre for signal transfer and a computer based data acquisition system.
AFRIKAANSE OPSOMMING: Standaard hoogspannings (HS) meettoerusting soos kapasitiewe spannmgs transformators het beperkte bandwydte vir die meet van wyeband verskynsels. Hierdie tesis handel oor die implementering van 'n HS meetstelsel wat op meinbrekende wyse oorgangsverskynsels meet deur middel van HS stroomtransformators wat in 'n transkonduktansie topologie gekonfigureer is. Die meet, sommasie en integrasie van kapasitoewe grondstrome word ondersoek. Hierdie tesis doen ook verslag aangaande die ontwikkeling van 'n optiese geisoleerde koppelvlak wat gebruik word vir seinoordrag en 'n rekenaar gebasseerde data versamelaar.
pdv201406
2
Bell, Simon Colin. "High-voltage partial-core resonant transformers". Thesis, University of Canterbury. Electrical and Computer Engineering, 2008. http://hdl.handle.net/10092/2161.
Testo completoAbstract (sommario):
This thesis first describes the reverse method of transformer design. An existing magnetic model for full-core shell-type transformers, based on circuit theory, is summarised. A magneto-static finite element model is introduced and two sample transformers are analysed. The magnetic model based on finite element analysis is shown to be more accurate than the model based on circuit theory.
Partial-core resonant transformers are then introduced and their characteristics are explained using an equivalent circuit model. A method of measuring the winding inductances under resonant operation is developed and used to investigate the characteristics of two different tuning methods. A finite element model of the partial-core resonant transformer is developed by adopting the model for full-core shell-type transformers.
The model results accurately match the measured inductance variation characteristics of three sample transformers and predict the onset of core saturation in both axial-offset and centre-gap arrangements. A new design of partial-core resonant transformer is arrived at, having an alternative core and winding layout, as well as multiple winding taps. The finite element model is extended to accommodate the new design and a framework of analysis tools is developed. A general design methodology for partial-core resonant transformers with fixed inductance is developed. A multiple design method is applied to obtain an optimal design for a given set of specifications and restrictions. The design methodology is then extended to devices with variable inductance.
Three design examples of partial-core resonant transformers with variable inductance are presented. In the first two design examples, existing devices are replaced. The new transformer designs are significantly lighter and the saturation effects are removed. The third design example is a kitset for high-voltage testing, with the capability to test any hydro-generator stator in New Zealand. The kitset is built and tested in the laboratory, demonstrating design capability. Other significant test results, for which no models have yet been developed, are also presented. Heating effects in the core are reduced by adopting an alternative core construction method, where the laminations are stacked radially, rather than in the usual parallel direction. The new kitset is yet to be used in the field.
3
Obatoyinbo, Ade. "Development of multi-layer on-package microwave baluns". Thesis, Georgia Institute of Technology, 2001. http://hdl.handle.net/1853/13557.
Testo completo
4
Jessee, J. Patrick. "A coupled thermal-magnetic finite element model for high frequency transformers". Thesis, This resource online, 1990. http://scholar.lib.vt.edu/theses/available/etd-12172008-063409/.
Testo completo
5
Minteer, Timothy Michael. "Design of a new transformer isolated analog acquisition system having greatly reduced transformer size and weight while achieving high accuracy". Online access for everyone, 2008. http://www.dissertations.wsu.edu/Thesis/Spring2008/t_minteer_041308.pdf.
Testo completo
6
Robalino, Vanegas Diego M. "Loss of life of medium voltage oil-immersed current transformers under thermal accelerated ageing a dissertation presented to the faculty of the Graduate School, Tennessee Technological University /". Click to access online, 2009. http://proquest.umi.com/pqdweb?index=0&did=1934058311&SrchMode=1&sid=2&Fmt=6&VInst=PROD&VType=PQD&RQT=309&VName=PQD&TS=1264684717&clientId=28564.
Testo completo
7
Lu, Shu. "Power transformer magnetization under GIC/GMD". Diss., This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-09232008-144706/.
Testo completo
8
Wacharasindhu, Tongtawee. "Fuse holder damage investigation". Diss., Columbia, Mo. : University of Missouri-Columbia, 2006. http://hdl.handle.net/10355/4599.
Testo completoAbstract (sommario):
Thesis (M.S.) University of Missouri-Columbia, 2006.The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on August 29, 2007) Includes bibliographical references.
9
Baningobera, Bwandakassy Elenga. "The IEC 61850 standard-based protection scheme for power transformers". Thesis, Cape Peninsula University of Technology, 2018. http://hdl.handle.net/20.500.11838/2713.
Testo completoAbstract (sommario):
Thesis (Master of Engineering in Electrical Engineering))--Cape Peninsula University of Technology, 2018.Transformer Differential and overcurrent schemes are traditionally used as main and backup protection respectively. The differential protection relay (SEL487E) has dedicated harmonic restraint function which blocks the relay during the transformer magnetizing inrush conditions. However, the backup overcurrent relay (SEL751A) applied to the transformer protection does not have a harmonic restraint element and trips the overcurrent relay during the inrush conditions. Therefore, to prevent the malfunction caused by the transformer magnetizing inrush current, a novel harmonic blocking method is developed, implemented and tested in the RSCAD simulation environment. The IEEE 14 bus transmission system is considered as a case study. The IEEE 14 bus system is modelled and simulated in the DIgSILENT and RSCAD simulation environments respectively. The developed harmonic blocking scheme is implemented in the Hardware-In-the-Loop (HIL) simulation environment using Real-Time Digital Simulator and numerical protection IEDs. The developed scheme uses the Harmonic Blocking element (87HB) of the transformer differential relay (SEL487E) to send an IEC61850 GOOSE-based harmonic blocking signal to the backup overcurrent relay (SEL751A) to inhibit it from tripping during the transformer magnetizing inrush current conditions. The hardwired and GOOSE simulation results are analysed for the transformer differential protection and the backup overcurrent protection schemes for internal, external events and transformer magnetizing inrush current conditions. The simulation results proved that the IEC61850 standard-based protection scheme is faster than the hardwired. Therefore, the speed and reliability are improved using the IEC61850 standard-based GOOSE applications to the transformer digital protective relaying system.
10
Habibi, Saeid. "Wireless charging of electric vehicles based on resonant inductive power transformers". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2019.
Cerca il testo completoAbstract (sommario):
Abstract
Electric vehicles and their charging stations are among important applications in today's world. The E-mobility industry is changing day-to-day with new ways to reduce charging time of electric vehicles, ease of use in charging process, increasing the efficiency and sometimes remote control access of the charging system.
To accomplish this, resonant inductive power transfers is one of the method that can be hired to transfer power to electric vehicles (EVs) over an air-gap and can remarkably improve the range, safety and convenience of the EV battery charging. However, implementation of a large scale wireless charging infrastructure of electric vehicles (e.g. for taxi fleet in a city) is still one of the major difficulties of such technology. Issues related to determining the physical sizes of the coil pads, standardization, technical interoperability, safety and designing the appropriate wireless charging system to be used for different EVs are among those difficulties.
The important target of doing this study is to understand the feasibility of installation of wireless charging stations for electric vehicle in terms of technical and financial issues, and understanding that which size of chargers are needed to install for electric vehicles. Electrical synchronization and interoperability of primary and secondary coils are other issues investigated. In the following chapters, financial and economic analysis of implementation of the wireless charging infrastructure for the taxi and van fleet in an urban area are discussed.
It can be concluded that implementation of wireless charging infrastructure for electric vehicles in urban areas for taxi fleet and delivery van drivers could bring many advantages because of specific working routine and stop time that they have during each working day. Increment of anxiety range, and reduction of charging time, convenience, being needless of tedious conventional charging cables, saving money are major advantages.
11
Edwards, John. "Magnetic flux based transformer model /". [St. Lucia, Qld.], 2002. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe16945.pdf.
Testo completo
12
Beckers, Peter C. "Design of a Self Regulated and Protected Electrification Transformer". Thesis, Link to the online version, 2007. http://hdl.handle.net/10019/335.
Testo completo
13
Makowski, Nathanael Jared. "Proposal and Analysis of Demagnetization Methods of High Voltage Power System Transformers and Design of an Instrument to Automate the Demagnetization Process". PDXScholar, 2011. https://pdxscholar.library.pdx.edu/open_access_etds/431.
Testo completoAbstract (sommario):
Present demagnetization methods for large power system transformers are time consuming and can be dangerous to persons performing demagnetization. The work of this thesis was to develop improved demagnetization methods and to construct an automated instrument that would implement the methods developed. One previously developed method was analyzed for effectiveness. Then, two new methods for demagnetization were developed and also analyzed for effectiveness. An automated test instrument prototype was redesigned to be able to accommodate these methods and to improve the safety of the user. The previously developed method attempts demagnetization based on current flow behavior characteristics. The first new method is a magnetic flux estimation based on saturation time. The second new method is also based on measuring saturation time, modified to account for the variable voltage loss due to wire resistance. The second of the two new methods developed proved to be the most effective for demagnetization and was able to demagnetize a transformer within an error margin of 2%. The instrument designed to perform the demagnetization with this new routine is now in early production stages for an expanded field trial with transformer maintenance teams.
14
Taberer, Marcel Wayne. "Transient analysis of erroneous tripping at grassridge static VAr compensator". Thesis, Nelson Mandela Metropolitan University, 2013. http://hdl.handle.net/10948/d1020918.
Testo completoAbstract (sommario):
The research work conducted and presented forward in this document is the evaluation of real time values obtained using three recording devices at two independent locations and implementing them as recorder devices in Eskom’s power system. The research work conducted was presented at an IEEE International Conference (ICIT2013) and Appendix A shows the accepted paper presented. A derived model within a simulation software package known as DIgSILENT PowerFactory is created and Electromagnetic Transient (EMT) studies are performed and then compared to the real time values obtained using the OMICRON CMC 356’s. Transformers are normally energised via a circuit breaker which is controlled by an auxiliary closing contact. By applying system voltage at a random instant in time on the transformer windings may result in a large transient magnetizing inrush current which causes high orders of 2nd harmonic currents to flow under no load conditions. A philosophy known to mitigate these currents is to energise the transformer by controlling each individual phase 120 degrees apart with the first pole closing at the peak on the voltage waveform. Transients produced due to 500MVA transformers been introduced into the power system at a certain space in time can cause nuisance tripping’s at the particular location where the respective transformer is energised. OMICRON EnerLyzer is the software tool used for the Comtrade recordings at both locations. Four independent case studies are generated within EnerLyzer software and the relevant Comtrade files are extracted for the four independent case studies relative to Transformer1 and Transformer2 switching’s. TOP software, which is a mathematical tool used to analyse Comtrade files, is then used to analyse and investigate the four case studies. Results from DIgSILENT PowerFactory are then generated according to the derived model. The results extracted depict three scenarios, indicating a power system that is weak, strong and specifically a power system that correlates to the actual tripping of a Static VAr Compensator (SVC). The results are all formulated and then evaluated in order to produce a conclusion and bring forward recommendations to Eskom in order to effectively ensure the Dedisa/Grassridge power system is reliable once again.
15
Zandberg, Hermanus Andries Jakobus. "Wireless transformer condition monitoring system". Thesis, Cape Peninsula University of Technology, 2013. http://hdl.handle.net/20.500.11838/1186.
Testo completoAbstract (sommario):
The Department of Electrical Engineering in fulfilment of the
requirements for the Magister Technologiae in Electrical
Engineering at the
Cape Peninsula University of Technology
November 2013Pole mounted transformers (PMT) in rural areas present an opportunity for local utilities to do current monitoring on these systems. These transformers are exposed to abnormal amounts of stress due to the vast power demand in these areas. The aim of this study is to develop a more cost-effective condition monitoring system. Transformer current monitoring can be a dangerous practice if not done by suitably trained utility electricians. Hence this study is partly aimed at the elimination of hazardous working environments associated with manual electrical measurements. An investigation to determine a safe and cost-effective way to obtain the electrical measurements required from PMTs is undertaken. Although current measurements can be done with a current clamp-on meter, these measurements still take place at the phases of the transformer and are unsafe. The possibility of implementing wireless data gathering on current clamp-on meters is therefore investigated. This is made possible by a wireless sensor node (WSN) which gathers information and transmits it wirelessly to a WSN base station. This wireless solution is battery powered, necessitating battery replacements, therefore leading to the investigation of magnetic fields, magnetic materials and magnetic induction. A current clamp able to generate a high voltage (HV) output with minimal magnetic field strength is developed. The magnetic fields produced by the transformer’s phase cables are used to generate an alternating voltage. With the help of a microcontroller and an energy harvesting circuit, this voltage is converted and used to charge supercapacitors. The magnetic fields are also used to determine the current flow in the transformer phase cables when the device is not in energy harvesting mode. The device will then undergo comprehensive laboratory testing to determine its accuracy and durability, and is then used to do ‘real life’ current measurements, the results of which are compared against an off-the-shelf current monitoring device.
16
Das, Debrup. "Dynamic control of grid power flow using controllable network transformers". Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/43739.
Testo completoAbstract (sommario):
The objective of the research is to develop a cost-effective, dynamic grid controller called the controllable network transformer (CNT) that can be implemented by augmenting existing load tap changing (LTC) transformers with an AC-AC converter. The concept is based on using a fractionally rated direct AC-AC converter to control the power through an existing passive LTC. By using a modulation strategy based on virtual quadrature sources (VQS), it is possible to control both the magnitude and the phase angle of the output voltage of the CNT without having any inter-phase connections. The CNT architecture has many advantages over existing power flow controllers, like absence of low frequency storage, fractional converter rating, retro-fitting existing assets and independent per-phase operation making it potentially attractive for utility applications.
The independent control of the magnitude and the phase angle of the output voltage allow independent real and reactive power flow control through the CNT-controlled line. In a meshed network with asymmetric network stresses this functionality can be used to redirect power from critically loaded assets to other relatively under-utilized parallel paths. The power flow controllability of CNT can thus be used to lower the overall cost of generation of power. The solid state switches in the CNT with fast response capability enable incorporation of various additional critical functionalities like grid fault ride through, bypassing internal faults and dynamic damping. This bouquet of features makes the CNT useful under both steady state and transient conditions without compromising the grid reliability.
17
Hamrita, Takoi K. "On-line digital signal processing methods for the correction of errors in high voltage power waveform measurements". Diss., Georgia Institute of Technology, 1993. http://hdl.handle.net/1853/15921.
Testo completo
18
Goad, Stephen D. "The theory and design of switched-mode power transformers for minimum conductor loss". Diss., Virginia Polytechnic Institute and State University, 1985. http://hdl.handle.net/10919/52290.
Testo completoAbstract (sommario):
A comprehensive and general analysis of the electromagnetic
fields, power dissipation, and energy storage
within transformer windings is presented. Emphasis is
placed on applications in switched-mode power conversion.
One-dimensional radial variation of the field quantities is
assumed.
The first phase of the investigation is for sinusoidal
excitation; solutions for the current density and magnetic
field intensity are derived and studied in order to develop
a fundamental understanding of the basic phenomena.
Expressions for the power dissipation and energy storage in
both single- and multi-layer windings are then derived
which, upon investigation, yield a technique for minimizing
the power dissipation by choosing an optimum conductor
thickness. Several levels of accuracy, ranging from exact
solutions to very simple and physically meaningful series
approximations, are defined and examined to determine their
usefulness and range of validity.
The time-harmonic treatment is generalized to arbitrary
periodic exoitation by means of Fourier analysis, resulting
in a powerful extension of its applicability to any possible
converter topology. Results for several representative
waveshapes are presented from which a fundamental dependence
cn the waveform bandwidth is discovered.
Practical application of the theoretical analysis is
considered by developing models for several couon winding
types: single and multi-filar round wire, litz wire, and
sheet conductors. Experimental results are presented and
compared with the theoretical results for each of these
cases. Finally, a design procedure is outlined for
switched—mode pour transformers which is based on this
work.Ph. D.
19
Hughes, Timothy Howard. "On the synthesis of passive networks without transformers". Thesis, University of Cambridge, 2014. https://www.repository.cam.ac.uk/handle/1810/265924.
Testo completoAbstract (sommario):
This thesis is concerned with the synthesis of passive networks, motivated by the recent invention of a new mechanical component, the inerter, which establishes a direct analogy between mechanical and electrical networks. We investigate the minimum numbers of inductors, capacitors and resistors required to synthesise a given impedance, with a particular focus on transformerless network synthesis. The conclusions of this thesis are relevant to the design of compact and cost-effective mechanical and electrical networks for a broad range of applications. In Part 1, we unify the Laplace-domain and phasor approach to the analysis of transformerless networks, using the framework of the behavioural approach. We show that the autonomous part of any driving-point trajectory of a transformerless network decays to zero as time passes. We then consider the trajectories of a transformerless network, which describe the permissible currents and voltages in the elements and at the driving-point terminals. We show that the autonomous part of any trajectory of a transformerless network is bounded into the future, but need not decay to zero. We then show that the value of the network's impedance at a particular point in the closed right half plane can be determined by finding a special type of network trajectory. In Part 2, we establish lower bounds on the numbers of inductors and capacitors required to realise a given impedance. These lower bounds are expressed in terms of the extended Cauchy index for the impedance, a property defined in that part. Explicit algebraic conditions are also stated in terms of a Sylvester and a Bezoutian matrix. The lower bounds are generalised to multi-port networks. Also, a connection is established with continued fraction expansions, with implications for network synthesis. In Part 3, we first present four procedures for the realisation of a general impedance with a transformerless network. These include two known procedures, the Bott-Duffin procedure and the Reza-Pantell-Fialkow-Gerst simplification, and two new procedures. We then show that the networks produced by the Bott-Duffin procedure, and one of our new alternatives, contain the least possible number of reactive elements (inductors and capacitors) and resistors, for the realisation of a certain type of impedance (called a biquadratic minimum function), among all series-parallel networks. Moreover, we show that these procedures produce the only series-parallel networks which contain exactly six reactive elements and two resistors and realise a biquadratic minimum function. We further show that the networks produced by the Reza-Pantell-Fialkow-Gerst simplification, and the second of our new alternatives, contain the least possible number of reactive elements and resistors for the realisation of almost all biquadratic minimum functions among the class of transformerless networks. We group the networks obtained by these two procedures into two quartets, and we show that these are the only quartets of transformerless networks which contain exactly five reactive elements and two resistors and realise all of the biquadratic minimum functions. Finally, we investigate the minimum number of reactive elements required to realise certain impedances, of greater complexity than the biquadratic minimum function, with series-parallel networks.
20
Flory, Isaac Lynnwood. "Modeling, analysis, and design of a 10 kVA, 20 kHz transformer". Thesis, This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-05042010-020300/.
Testo completo
21
Phillips, Lyndal, University of Western Sydney, of Science Technology and Environment College e of Science Food and Horticulture School. "Analysis of polychlorinated biphenyls in transformer oils". THESIS_CSTE_SFH_Phillips_L.xml, 2002. http://handle.uws.edu.au:8081/1959.7/766.
Testo completoAbstract (sommario):
Polychlorinated Biphenyls (PCBs) were seen as a significant engineering advance when first commercially produced in 1929. They were used as insulators and cooling fluids in electrical transformers and capacitors. There are 209 PCB congenors that are chemically and thermally stable with low inflammability and reactivity. However,they are also highly toxic, suspected carcinogens and bioaccumulate in the food chain. Due to these characteristics they are listed by the United Nations as one of the sixteen worlds persistent organic pollutants POPs). By international agreement, undertaken by the UN, the production of PCBs has been banned and gradually their use will be phased out. Several tests and procedures are discussed in some detail in this research.Master of Science (Hons)
22
Mousavi, Takami Kourosh. "Process Control and Simulation of Ferromagnetic Strip in the Power Transformers and Electrical Machines Applications : Electric power systems". Doctoral thesis, Västerås : School of Sustainable Development of Sociaty and Technology, Mälardalen University, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-6648.
Testo completo
23
Li, Xun. "Physical systems for the active control of transformer noise". Title page, contents and abstract only, 2000. http://hdl.handle.net/2440/37964.
Testo completoAbstract (sommario):
Traditional means of controlling sound radiated by electrical power transformers involve the construction of large expensive barriers or full enclosures, which cause maintainability and cooling problems. One promising alternative is to use active noise control to cancel the noise. This thesis is concerned with one of the many problems which need to be investigated to develop a practical active noise cancellation system for transformers. This work, in particular, is concerned with the physical system design which includes the selection of the control source types and the evaluation of the near-field sensing strategies. Loudspeakers have been widely used in the past as an acoustic source for canceling transformer noise. The principal disadvantage of using loudspeakers is that to achieve global noise control, a large number, driven by a multi-channel controller, are required. However, if large panels are used in place of loudspeakers as control sources, it is possible that the number of the control sources and complexity of the controller could be reduced substantially. In addition to reducing the number of control sources and simplifying their application, panel sound sources could also overcome some disadvantages of the loudspeakers, such as limited life and deterioration due to the weather. Thus, part of the work described in this thesis is concerned with the development of a resonant curved panel with a backing cavity as an acoustic type source. The advantages of using a curved panel rather than a flat panel are twofold: first a curved panel is more easily excited by the extensional motion of the piezoelectric patch actuators; and second, it is more difficult to adjust the resonance frequencies of the efficient modes of a flat panel than of a curved panel. The analytical models for the design of the panel cavity systems have been developed. As an example, a resonant curved panel with a backing cavity system was constructed and the sound radiation of the system was measured. Results show that a resonant panel-cavity sound source could be used as an alternative to a number of loudspeakers for active cancellation of electric power transformer noise. Due to the advantages of using the vibration type control sources, two types of vibration control sources (inertial electrodynamic shakers and piezoelectric patch actuators) were considered and the mechanical output of the inertial shakers has been compared with that of the piezoelectric actuators. In contrast with the piezoelectric actuators, the resonance frequencies of the inertial shakers can be tuned to the frequencies of interest using simple tuning procedures, so that the output efficiency of the shakers can be increased. The output performance was evaluated for two types of actuators by measuring the structural response of either a panel or a transformer when excited by the actuators at half their rated voltage input. Results demonstrated that a much larger output amplitude at the frequency of interest can be achieved by the tuned inertial type actuators. Two near-field sensing strategies, the minimization of the sum of the sound intensities and the minimization of the sum of the squared sound pressures, have been studied. A quadratic expression was derived for the minimization of the sum of the sound intensities in the near-field. To evaluate the control performances achieved using both sensing strategies, a flat-panel was modelled with a harmonic point force disturbance and several point force control sources. Simulation results show that the control performance could be improved by minimizing the sum of the sound intensities in the hydrodynamic near-field, provided that a very large number of error sensors were used, otherwise better results were achieved using near-field squared pressure sensing. Both sensing strategies were used to predict the noise reductions that resulted for the active noise control of a small transformer in the laboratory environment and for a large electrical power transformer on site. To optimize the locations of the control sources (for the large transformer on site) and the locations of the error sensors (for the small transformer in the laboratory environment), a genetic algorithm (GA), which is an evolutionary optimization technique, was employed as a search procedure to optimize the control source and error sensor locations. The results showed that the control source locations and/or the error sensor locations must be optimized to achieve the maximum sound reduction for either error sensing strategy, especially for the sound intensity minimization; otherwise, the sound field level may increase after control due to the character of the cost function (the sum of the sound intensities). The simulation results were experimentally validated for the small transformer in the laboratory environment. Due to the limitation of the number of controller channels, the control performance was only evaluated for squared pressure minimization. The results demonstrated that for the case of 8 control sources and 8 error sensors, at 100 Hz, an average sound pressure reduction of 15.8 dB was achieved when evaluated at 528 monitoring locations at 0.25 m intervals on a surface that surrounded the transformer.Thesis (Ph.D.)--Engineering (Department of Mechanical Engineering), 2000.
24
Yao, Zheng Tong. "Analysis and modelling of dielectric response in power transformer insulation /". [St. Lucia, Qld.], 2003. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe16984.pdf.
Testo completo
25
Santos, Luciano dos. "Cálculo das perdas técnicas dos transformadores de distribuição, operando em ambiente não-senoidal /". Ilha Solteira : [s.n.], 2006. http://hdl.handle.net/11449/87245.
Testo completoAbstract (sommario):
Orientador: José Carlos RossiBanca: Fabio Toshiaki Wakabayashi
Banca: Kleiber David Rodrigues
Resumo: Este trabalho está direcionado à implementação de uma modelagem que venha possibilitar a realização dos cálculos das perdas técnicas no cobre do transformador trifásico de distribuição operando em condições não-senoidais, através da utilização do valor médio de Distorção Harmônica Total de Corrente drenada por suas cargas. Essa implementação visa facilitar a obtenção dos valores das perdas técnicas para múltiplas unidades transformadoras. Para atingir o objetivo mencionado, realizou-se um ensaio em curto-circuito através de ensaios experimentais aplicadas em uma unidade transformadora trifásica de distribuição com 15 kVA de capacidade. A fonte trifásica de alimentação utilizada na atividade proporciona o ajuste de tensão e da freqüência, possibilitando obter os valores de resistências CA dos enrolamentos do transformador para diferentes ordens harmônicas. Com o propósito de validar esta nova proposta, foi realizada uma análise confrontando-se os dados obtidos através da modelagem proposta neste trabalho e de uma outra bastante difundida pela literatura atual. Os cálculos foram efetuados utilizando-se dados de distorções harmônicas de correntes oriundas de medições de ramais de distribuição. Através da comparação dos resultados obtidos é possível verificar a validade da modelagem proposta.
Abstract: This work is addressed to the implementation of a modeiling that comes to make possible the calculations of the technical losses in the copper of three-phase distribution transformers operating under non-sinusoidal conditions, using the médium value of Total Current Harmónio Distortion. This implementation seeks to provide easiness in the obtaining of the values of the technical losses for multiple transformer units in non-sinusoidal environment. Aiming to reach the mentioned objective, it was carried out a test in short circuit through appiied experimental activities in a three-phase distribution transformer unit with 15 k VA capacity. The three-phase source used in the activity provides the voltage and the frequency adjustment, making possible to obtain the values ofca resistances ofthe windings ofthe transformer for some harmónio orders. With the purpose ofvalidating this new proposal, an analysis was accomplished being confronted the data obtained through the modeiling proposed in this work with another one quite spread in the current literature. The calculations were carried out using current harmónio distortion data of measurements in distribution branch lines. Through the comparison of the obtained results it is possible to verify the validity ofthe proposed modeiling.
Mestre
26
Benwell, Andrew L. Kovaleski Scott D. "A high voltage piezoelectric transformer for active interrogation". Diss., Columbia, Mo. : University of Missouri--Columbia, 2009. http://hdl.handle.net/10355/6847.
Testo completoAbstract (sommario):
Title from PDF of title page (University of Missouri--Columbia, viewed on Feb 23, 2010). The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file. Dissertation advisor: Dr. Scott D. Kovaleski. Vita. Includes bibliographical references.
27
Gean, Richard T. "Comparison of PWM and resonant technologies in a high voltage DC application". Thesis, Virginia Tech, 1990. http://hdl.handle.net/10919/42080.
Testo completoAbstract (sommario):
High voltage transformers inherently contain undesirable parasitic reactances. A resonant circuit formed by the leakage inductance and parasitic reflected capacitance, makes various resonant technologies practical for high voltage dc applications. The components of a typical high voltage power stage will be investigated in order to identify these parasitics and determine their influence on converter operation. Proto-type high voltage converters will be designed and built using PWM and quasi-resonant techniques and experimental results will be given.
Dc analysis will be performed for the PWM and the quasi-resonant designs in order to obtain insight into the actual operation of the two converters. The design of the two proto-type converters will be reviewed and design guidelines will be established.
Master of Science
28
Phillips, Lyndal. "Analysis of polychlorinated biphenyls in transformer oil /". View thesis, 2002. http://library.uws.edu.au/adt-NUWS/public/adt-NUWS20031222.095244/index.html.
Testo completoAbstract (sommario):
Thesis (M.Sc.) (Hons.) -- University of Western Sydney, 2002.A thesis submitted to the University of Western Sydney in fulfillment of the requirements for admission to the [degree of] Masters of Science (Honours). Bibliography : leaves 156-163.
29
Turkmen, Coskun Aziz. "Calibration Of Conventional Measurement Transformers Against Harmonic Components By Using Field Measurements Of Optical Transducers And Resistive-capacitive Voltage Transformers". Master's thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/12611920/index.pdf.
Testo completoAbstract (sommario):
It is known from the literature that conventional voltage and current transformers measure inaccurate values for voltage and current harmonics which are parts of power quality. Maximum bandwidth of conventional current transformers, which are used in electricity transmission and distribution systems, is 1.5-2 kHz and it is lower for conventional voltage transformers. Also, it is known thatvoltages in some frequency spectrum are measured higher and voltages in another frequency spectrum are measured lower by the conventional voltage transformers. Furthermore, because of the phase shift of fundamental component caused by the conventional current and voltage transformers, losses and efficiency can not be calculated accurately. In this work, through the simultaneous measurements taken at the same feeder by both conventional transformers and new technology measurement transformers
amplitude and phase shift errors which are caused by conventional transformers depending on frequency and so harmonics, are examined and evaluated. Amplitude coefficients and phase shifts are determined for different types of conventional transformers to be able to calibrate measurement deviation. Through this work, measured data by conventional transformers will be accurate and realistic in terms of harmonic components. This matter is important to determine whether the accurate limits which will be set in the future possibly concerning with harmonics and interharmonics, are surpassed or not
also for punitive sanction.
30
Johansson, Nicklas. "Control of Dynamically Assisted Phase-shifting Transformers". Licentiate thesis, Stockholm : Elektrotekniska system, Kungliga Tekniska högskolan, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4653.
Testo completo
31
Roman, Matthew Jang Wooseung. "Disaggregate forecasting models application to Ameren UE's transformer usage /". Diss., Columbia, Mo. : University of Missouri--Columbia, 2008. http://hdl.handle.net/10355/5738.
Testo completoAbstract (sommario):
The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file. Title from PDF of title page (University of Missouri--Columbia, viewed on October 5, 2009). Thesis advisor: Dr. Wooseung Jang. Includes bibliographical references.
32
Van, Jaarsveld Barend Jacobus. "Wide-band modelling of an air-core power transformer winding". Thesis, Stellenbosch : Stellenbosch University, 2013. http://hdl.handle.net/10019.1/85823.
Testo completoAbstract (sommario):
Thesis (MScEng)-- Stellenbosch University, 2013.ENGLISH ABSTRACT: The objective of this project is to develop an electromagnetic model that can be used to accurately calculate the voltage distribution in a transformer winding structure when excited with standard impulse excitation waves. This voltage distribution is required during the design stage of a power transformer to ensure that the insulation is capable of withstanding the occurring electric field stresses during these tests. This study focuses on the modelling of a single disk-type power transformer winding without the presence of an iron-core. Methods of calculating self- and mutual-inductances of transformer windings are presented and validated by means of finite element method software simulations. The same is done for the calculation methods used for calculating the capacitances in and around the winding structure. The calculated and FEM-simulated results are compared to measured values as a final stage of validation. The methods used to calculate the various model parameters seem to produce results that agrees well with measured values. The non-linear frequency dependant dissipative nature of transformer windings is also investigated and a methodology to take this into account is proposed and implemented. The complete modelling methodology proposed in this thesis, which includes the calculation of the model parameters, model synthesis and solver algorithm, are applied to an actual case study. The case study is performed on an air-core reactor manufactured using a disk-type power transformer winding. The reactor is excited with standard lightning impulse waves and the voltages along the winding are measured. The calculated and measured voltage wave forms are compared in both the frequency and time-domain. From the comparison it is found that the model accurately represents the actual transient voltage response of the testunit for the frequency range of interest during standard factory acceptance tests.
AFRIKAANSE OPSOMMING: Die doel van hierdie projek is om 'n elektromagnetiese model te ontwikkel wat gebruik kan word om die spanningsverspreiding in 'n transformatorwindingstruktuur te bereken as standaard weerligimpulstoetse toegedien word. Hierdie spanningsverspreiding word vereis tydens die ontwerpstadium van ‘n kragtransformator om te verseker dat die isolasie in staat is om die elektriese veldsterkte tydens hierdie toetse te weerstaan. Hierdie studie fokus op die modelering van 'n enkele skyftipe-kragtransformatorwinding sonder die teenwoordigheid van 'n ysterkern. Metodes van berekening van self- n wedersydse-induktansie van transformatorwindings word aangebied en getoets deur middel van Eindige-Element-Metode (EEM) simulasies. Dieselfde word gedoen vir die metodes wat gebruik word vir die berekening van die kapasitansies in en rondom die windingstruktuur. Die berekende en EEM-gesimuleerde resultate word vergelyk met die gemeete waardes as 'n finale vlak van bekragtiging. Die metodes wat gebruik word om die verskillende modelparameters te bereken vergelyk goed met gemete waardes. Die nie-lineêre frekwensie-afhanklike verliese van transformatorwindings word ook ondersoek en 'n metode om hierdie in ag te neem is voorgestel en geïmplementeer. Die volledige voorgestelde modeleringsmetodiek in hierdie tesis, wat die berekening van die modelparameters, modelsintese en oplosingsalgoritme insluit word toegepas op 'n werklike gevallestudie. Die gevallestudie is uitgevoer op 'n lugkern-reaktor wat 'n skyftipe-kragtransformatorwinding. Die reaktor word onderwerp aan die standaard weerligimpuls golwe en die spanning al langs die winding word gemeet. Die berekende en gemete spanning golf vorms word met mekaar vergelyk in beide die frekwensie- en tyd-vlak. Uit die vergelyking blyk dit dat die model die werklike oorgangspanningsweergawe van die toetseenheid akkuraat verteenwoordig vir die frekwensie reeks van belang tydens standaard fabriekaanvaardingstoetse.
33
Ntwoku, Stephane Ntuomou. "Dynamic transformer protection a novel approach using state estimation". Thesis, Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/45879.
Testo completoAbstract (sommario):
Transformers are very important parts of any electrical network, and their size increase so does their price. Protecting these important devices is a daunting task due to the wide variety of operating conditions. This thesis develops a new protection scheme based on state estimation.The foundation upon which our protection scheme is built is the modeling of the single phase transformer system of equations. The transformer equations are composed of polynomial and differential equations and this system of equations involving the transformer's electrical quantities are modeled into a system of equations such that highest degree of each of the system's equations is quadratic―in a process named Quadratization and then integrated using a technique called Quadratic integration to give a set of algebraic companion equations that can be solved numerically to determine the health of the transformer.
34
Lesser, Beverly Brown. "Thermal-magnetic finite element model of a high frequency transformer". Thesis, Virginia Tech, 1989. http://hdl.handle.net/10919/44121.
Testo completoAbstract (sommario):
In high-frequency power transformers, magnetic material properties cannot be assumed to be constant. These properties vary with frequency, temperature, and magnetic flux density. Heat generation is, in turn, a function of the magnetic permeability, magnetic flux density, and frequency. Current design methods are either empirical or based on linear, uncoupled models. To better understand the relationship between heat transfer, magnetic flux density, material properties, and core geometry in a miniature, high-frequency transformer, a finite-element program has been developed to solve the coupled thermal-magnetic equations for an axisymmetric transformer. The program accounts for nonlinear temperature and magnetic field dependent material properties, geometry, and driving frequency.
The program, HT-MAG, is based on a series of derived magnetic field equations. The Ritz method is applied to the magnetic and thermal equations in the development of the program. The program alternately solves the finite element approximations to the thermal and magnetic governing equations until the magnetic properties match within a specified fraction or a maximum number of iterations are performed. In addition, the program can be linked with existing pre- and post-processors or can accept manual pre- and post-processing.
Six test cases were run to test the validity of the program. The first two cases tested the uncoupled heat transfer calculations. One of these tested the thermal conduction calculations while the other tested the heat generation calculations. The next two cases tested the uncoupled magnetic equations. The first was a direct current (DC) case, while the second was an alternating current (AC) case. The final two cases tested the thermal magnetic coupling. Solutions to these cases are presented and discussed.
Master of Science
35
Gradzki, Pawel Miroslaw. "Core loss characterization and design optimization of high-frequency power ferrite devices in power electronics applications". Diss., This resource online, 1992. http://scholar.lib.vt.edu/theses/available/etd-06062008-165934/.
Testo completo
36
Chetty, Manogaran. "Reliability analysis of power transformers : case : Eskom Distribution Eastern Region, 1MVA to 80MVA power transformers". Thesis, 2007. http://hdl.handle.net/10413/5447.
Testo completoAbstract (sommario):
This dissertation analyses the reliability of power transformers and its impact of failure on system performance. Eskom Distribution, Eastern Region is used as a practical case study, which has an installed transformer base of 6066MVA comprising of 428 transformers ranging from 1 MVA to 8OMVA with voltage levels of 6.6kV to I 32kV. The literature review illustrates the theory and principles of transformers, evolution and changes in design criteria, the function of cellulose and insulating oil, failure modes. operations and
maintenance practices and factors affecting the distribution systems performance. This study included a conditional assessment and an oil analysis review of transformers at Eskom. A method to trend multiple oil samples was developed and illustrated. The research further investigates the reliability of series and parallel systems using actual component reliability values. A study was conducted to establish the degree of network firmness. Transformer failure data was analysed and were shown to be characteristic of a bathtub curve. Defects from on site inspections were analysed and identified oil leaks as a maintenance focus area. The Distribution Supply Loss Index was determined to be the major impact Key Performance Index due to transformer failures. Transformer failures using statistical methods, showed HV/LV winding to be the main component to fail. The cost of a transformer
failure to Eskom and the customer was determined. International Benchmarking was investigated to establish the criteria for network reliability
indices and to compare the network infrastructure and performance of international utilities and Eskom. The later part of the study involved the analysis of a risk ranking methodology to establish a risk ranking matrix. The transformers were ranked according to the matrix, identifying the high risk focus areas. Projects were raised within Eskom to replace the identified
high risk transformers. This study has concluded that the reliability of transformers is impacted by the changes in transformer design, increased maintenance defects and inadequate transformer protection at substations. The reduced oil volume per kVA, increased hot spot and ambient temperature, and compact tank designs have resulted in the cellulose being overheated and fault gases being produced during normal operating conditions. The increase in load demand from the existing transformer fleet and a reduction in capital expenditure to maintain and build additional substations have also contributed to accelerated aging, since the transformers are forced to operate at 100 percent loading. There is an increase in transformer maintenance defects due to in sufficient operational staff, high staff turnover, reduced skills transfer. and insufficient network contingencies to allow for planned outages to clear the defects identified. The failure analysis showed that the main component to fail is HV/LV windings. The winding failures were traced to there being no or inadequate transformer protection at -20% of substations.Thesis (M.Sc.)-University of KwaZulu-Natal, 2007.
37
Zheng, Kai-En, e 鄭凱恩. "Impacts of Electric Vehicle Charging on Electric Power Transformers". Thesis, 2013. http://ndltd.ncl.edu.tw/handle/65586314029181111820.
Testo completoAbstract (sommario):
碩士國立高雄海洋科技大學
輪機工程研究所
101
Electric vehicle (EV) battery charging can be potentially large power system load. Thus, it is important to examine the effect that wide-spread EV charging may have no the power distribution system so that an accurate and realistic assessment can be made of the infrastructure changes needed. The aim of this thesis is to study the effect EV charging on a distribution transformer that supplies dedicated EV load. The EV load is modeled using the results from the measurements of EV charging stations for predicting the net power and harmonic currents generated by a group of EV battery chargers. The effect of EV load on the distribution transformer is evaluated using ANSI/IEEE standards for transformer loading and the effect of nonlinear current on power system devices is illustrated. To reduce effects of variations in input parameters on analysis results, a sensitivity analysis that considering variations in base load, EV amount, transformer rating, ambient temperature, and transformer connection impact on the loss-of-life (LOL)of the transformer is also performed. Test results have shown that base load and ambient temperature can have a significant impact on the transformer LOL. Analysis results can provide utilities and charging station operators useful information forplanning, designing, and managing the transformer and EV.
38
Baltazar, José Paulo Barbosa. "Modelling vertical plate radiatores for electric transformers". Master's thesis, 2014. https://repositorio-aberto.up.pt/handle/10216/88156.
Testo completo
39
Baltazar, José Paulo Barbosa. "Modelling vertical plate radiatores for electric transformers". Dissertação, 2014. https://repositorio-aberto.up.pt/handle/10216/88156.
Testo completo
40
Strydom, Johan Tjeerd. "Electromagnetic design of integrated resonator-transformers". Thesis, 2009. http://hdl.handle.net/10210/2182.
Testo completoAbstract (sommario):
D.Ing.In the field of power electronics, the relentless demand for higher efficiencies, lower costs and ever-decreasing volume and profile have driven the development of many innovative technologies. Planarization and hybridization have become a substantial part of present system integration methodology. With the subsequent size reduction, the effects of layout and component parasitics are becoming vital issues in the development of innovative structures. The component ‘parasitics’ can be considered dimensional effects of the component structure that are not considered during the design process. The concept of electromagnetic integration is aimed at the utilization and modification of these dimensional effects. This leads to an integrated structure that fulfills multiple electromagnetic functions with the potential for improved power density, efficiency and reliability. In this dissertation, a family of electromagnetically integrated passives is presented. The related electromagnetic modeling and design approach of these complex electromagnetic structures is presented through a case study of L-L-C-T structures. The development of a sufficiently accurate, yet simplified electromagnetic model for design purposes is presented for the case study. With the electromagnetic model as basis, a comprehensive electromagnetic loss model is created. The electromagnetic design and loss models are combined into a design evaluation program. The graphical output of this design evaluation program allows for rapid selection of improved designs based on external cost criteria. This led to numerous insights into the relationships between the design variables. Through modification of the program, some fundamental limits of the integration approach are addressed. A case study design for a 1MHz, 500W dc-dc converter was considered to evaluate the design program. To assess the accuracy of the electromagnetic modeling, three L-L-C-T prototypes are constructed and experimentally tested. The construction process presented improved power density by 80% over previous processes. The electromagnetic component parameters for three prototypes were within 10% of the required design values, while the electromagnetic loss model estimations were within measurement error. The design evaluation program was enlisted in the design of two of these prototypes. This resulted in a 100% further improvement in power density (480W/in3 or 29.3W/cm3) compared to the original prototype without a loss in efficiency.
41
"Condition monitoring of transformers : the acoustic method". Thesis, 2010. http://hdl.handle.net/10413/1461.
Testo completo
42
Van, Deventer M. J. "Hydrogen gas-in-oil on-line monitor for high voltage current transformers". Thesis, 1991. https://hdl.handle.net/10539/26635.
Testo completoAbstract (sommario):
A dissertation submitted to the Faculty of
Engineering, University of the Witwatersrand,
Johannesburg, in fulfilment of the requirements for
the degree of Master of Science in Engineering.The sudden failure of oil paper-insulated current transformers has become a problem of considerable concern due to the cost of the resulting destruction, and danger to personnel. The aim of the dissertation is. to determine the most suitable method of detecting lncipient faults in current transformers, test this method on an experimental current transformer, and finally implement this technique in a low cost on-line monitor. A literature survey indicated that hydrogen gas-in-oil on-line monitoring would be the most suitable technique.(Abbreviation abstract)
Andrew Chakane 2019
43
Mukherjee, Pritam. "Construction Of Equivalent Circuit Of A Single Isolated Transformer Winding From Frequency Response". Thesis, 2011. https://etd.iisc.ac.in/handle/2005/2055.
Testo completoAbstract (sommario):
Frequency response analysis (FRA) of transformers is universally accepted as a highly sensitive tool to detect deformations in its windings. This is evident from the fact that customized commercial equipment (popularly called FRA or SFRA instruments) are used and recently the IEEE has issued a draft trial-use guide. Nevertheless, use of FRA is still limited to only detection and there is little progress towards its use for localization of winding deformation. Toward this end, a possible approach would be to compare the healthy and deformed systems in a suitable domain, e.g., their respective models could be compared. In this context, the mutually-coupled ladder network is ideally suited because not only does it map the length of the winding to sections of the ladder network, but, also inherently captures all subtle intricacies of winding behaviour under lightning impulse excitations insofar as the terminal response, internal oscillations and voltage distributions are concerned. The task of constructing a ladder network from frequency response is not trivial, and so exploration of newer methods is imperative.
A system can comprehensively be characterized by its frequency response. With this as the starting point, many approaches exist to construct the corresponding rational function (in s-domain). But, the subsequent step of converting this rational function into a physically-realizable mutually-coupled ladder network has, as yet, remained elusive. A critical analysis of the circuit synthesis literature reveals that there exists no analytical procedure to achieve this task, a fact unequivocally stated by Guillemin in his seminal book "Synthesis of Passive Networks". In recent years, use of iterative methods to synthesize such ladder networks has also been attempted with some degree of success. However, there exists a lot of scope for improvement. Based on this summary, the objectives of this thesis are as follows-
_ Development of an analytical procedure, if possible, to synthesize a mutually-coupled ladder network starting from the s-domain representation of the frequency response
_ Construction of a nearly-unique, mutually-coupled ladder network employing
constrained optimization technique and using frequency response as input, with
time-efficiency, physical realizability and repeatability as its features
In Chapter 2, analytical solution is presented to convert a given driving-point impedance function (in s-domain) into a physically-realizable ladder network with inductive couplings (between any two sections) and losses considered. The number of sections in the ladder network can vary, but, its topology is assumed fixed. A study of the coefficients of the numerator and denominator polynomials of the driving-point impedance function of the ladder network, for increasing number of sections, led to the identification of certain coefficients, which exhibit very special properties. Generalized expressions for these specific coefficients have also been derived. Exploiting their properties, it is demonstrated that the synthesis method essentially turns out to be an exercise of solving a set of linear, simultaneous, algebraic equations, whose solution directly yields the ladder network elements. The proposed solution is novel, simple, and guarantees a unique network. Presently, the formulation can synthesize a unique
ladder network up to 6-sections. Although it is an analytical solution, there are issues which prevent its implementation with actual FRA data.
Keeping the above aspect in mind, the second part of the thesis presents results
of employing an artificial bee colony search algorithm for synthesizing a mutuallycoupled lumped-parameter ladder network representation of a transformer winding, starting from its measured magnitude frequency response. The bee colony algorithm is modified by defining constraints and bounds to restrict the search-space and thus ensure synthesis of a nearly-unique ladder network, corresponding to each frequency response. Ensuring near-uniqueness while constructing the reference circuit (i.e., a uniform healthy winding) is the objective. The proposed method is easy to implement, time-efficient, ensures physical realizability and problem associated with supply of initial guess in existing methods is circumvented. Experiments were performed on two types of actual, single, isolated transformer windings (continuous-disc and interleaveddisc) and the results are encouraging.
Further details are presented in the thesis.
44
Mukherjee, Pritam. "Construction Of Equivalent Circuit Of A Single Isolated Transformer Winding From Frequency Response". Thesis, 2011. http://etd.iisc.ernet.in/handle/2005/2055.
Testo completoAbstract (sommario):
Frequency response analysis (FRA) of transformers is universally accepted as a highly sensitive tool to detect deformations in its windings. This is evident from the fact that customized commercial equipment (popularly called FRA or SFRA instruments) are used and recently the IEEE has issued a draft trial-use guide. Nevertheless, use of FRA is still limited to only detection and there is little progress towards its use for localization of winding deformation. Toward this end, a possible approach would be to compare the healthy and deformed systems in a suitable domain, e.g., their respective models could be compared. In this context, the mutually-coupled ladder network is ideally suited because not only does it map the length of the winding to sections of the ladder network, but, also inherently captures all subtle intricacies of winding behaviour under lightning impulse excitations insofar as the terminal response, internal oscillations and voltage distributions are concerned. The task of constructing a ladder network from frequency response is not trivial, and so exploration of newer methods is imperative.
A system can comprehensively be characterized by its frequency response. With this as the starting point, many approaches exist to construct the corresponding rational function (in s-domain). But, the subsequent step of converting this rational function into a physically-realizable mutually-coupled ladder network has, as yet, remained elusive. A critical analysis of the circuit synthesis literature reveals that there exists no analytical procedure to achieve this task, a fact unequivocally stated by Guillemin in his seminal book "Synthesis of Passive Networks". In recent years, use of iterative methods to synthesize such ladder networks has also been attempted with some degree of success. However, there exists a lot of scope for improvement. Based on this summary, the objectives of this thesis are as follows-
_ Development of an analytical procedure, if possible, to synthesize a mutually-coupled ladder network starting from the s-domain representation of the frequency response
_ Construction of a nearly-unique, mutually-coupled ladder network employing
constrained optimization technique and using frequency response as input, with
time-efficiency, physical realizability and repeatability as its features
In Chapter 2, analytical solution is presented to convert a given driving-point impedance function (in s-domain) into a physically-realizable ladder network with inductive couplings (between any two sections) and losses considered. The number of sections in the ladder network can vary, but, its topology is assumed fixed. A study of the coefficients of the numerator and denominator polynomials of the driving-point impedance function of the ladder network, for increasing number of sections, led to the identification of certain coefficients, which exhibit very special properties. Generalized expressions for these specific coefficients have also been derived. Exploiting their properties, it is demonstrated that the synthesis method essentially turns out to be an exercise of solving a set of linear, simultaneous, algebraic equations, whose solution directly yields the ladder network elements. The proposed solution is novel, simple, and guarantees a unique network. Presently, the formulation can synthesize a unique
ladder network up to 6-sections. Although it is an analytical solution, there are issues which prevent its implementation with actual FRA data.
Keeping the above aspect in mind, the second part of the thesis presents results
of employing an artificial bee colony search algorithm for synthesizing a mutuallycoupled lumped-parameter ladder network representation of a transformer winding, starting from its measured magnitude frequency response. The bee colony algorithm is modified by defining constraints and bounds to restrict the search-space and thus ensure synthesis of a nearly-unique ladder network, corresponding to each frequency response. Ensuring near-uniqueness while constructing the reference circuit (i.e., a uniform healthy winding) is the objective. The proposed method is easy to implement, time-efficient, ensures physical realizability and problem associated with supply of initial guess in existing methods is circumvented. Experiments were performed on two types of actual, single, isolated transformer windings (continuous-disc and interleaveddisc) and the results are encouraging.
Further details are presented in the thesis.
45
Sumangala, B. V. "Some Aspects Of Surge Voltage Distribution In Transformers With Enhanced Resolution". Thesis, 2004. https://etd.iisc.ac.in/handle/2005/1181.
Testo completo
46
Sumangala, B. V. "Some Aspects Of Surge Voltage Distribution In Transformers With Enhanced Resolution". Thesis, 2004. http://etd.iisc.ernet.in/handle/2005/1181.
Testo completo
47
Swart, Barend Jacques. "Manufacturability improvements of high frequency transformers". Thesis, 2014. http://hdl.handle.net/10210/9413.
Testo completoAbstract (sommario):
M.Ing. (Electrical and Electronic Engineering)In order to improve the industrialisation of modern power converters, its physical size must be reduced, material must be utilised more efficiently and its manufacturability improved. Consequently, many converters are operated in the ultrasonic frequency range, where the size of its constituent components are considerably reduced. Even at high frequencies of operation, however, magnetic components are still the largest and heaviest components in converters, and do not utilise materials to their maximum benefit. The aim of this work is to investigate the possibility of improving the industrialisation of power electronic converters by making use of a novel, multiple core magnetic component structure, called the distributed transformer. Existing magnetic component structures are evaluated from a materials point of view and the concept of distributed magnetic components introduced. A generalised transformer model is developed for the distributed transformer and pertinent design considerations discussed. A 1.5 kw battery charger industrialised by Spoornet is based on the CukDC-DC converter and is used as a case study. A conventional monolithic isolation transformer is used in its construction after a complete mathematical analysis of the converter topology, and compared with the equivalent distributed transformer configuration. The distributed transformer is then compared with the conventional monolithic transformer and evaluated in terms of its physical and electrical performance, design and ease of manufacture.
48
Minhas, Muhammad Salman Aslam. "Dynamic behaviour of transformer winding under short-circuits". Thesis, 2008. http://hdl.handle.net/10539/4764.
Testo completoAbstract (sommario):
The work presented in this thesis contributes to the understanding of the
dynamic behaviour of large power transformer windings under short circuit
forces. A simple yet accurate method of prediction of electromagnetic forces
is developed and used as input to the dynamic mechanical model. In develop-
ing this model the mechanical properties of oil-impregnated pressboard have
been investigated and measured in a specially designed rig which simulates
the typical power transformer environment. Assumptions have been made
regarding these properties to enable them to be meaningfully incorporated in
a dynamic model of a transformer. Predictions made using the model have
been compared with actual measurements on a transformer and a correlation
within 20%-30% was achieved. The work demonstrated the importance of
mechanical prestress to ensure that no serious nonlinearities will be encoun-
tered in the mechanical behaviour when short-circuit forces are present in a
power transformer. It was also found that for small radial deflections, the
axial and radial behaviours are independent. This work provides a theoreti-
cal basis for further work in which precise determinations of the mechanical
properties of oil-impregnated pressboard can be used to model the dynamic
behaviour of a large transformer to a high degree of accuracy.
49
Van, der Merwe Gabriel Jacobus. "Integreerbare stuurtegnologie vir bipolere drywingselektroniese skakelaars tot 2000 A". Thesis, 2014. http://hdl.handle.net/10210/9295.
Testo completoAbstract (sommario):
M.Ing. (Electrical and Electronic Engineering)In an attempt to build a 2000A transistor switch. with the possibility of integrating the electromagnetic components, different transistor switch and transformer configurations were investigated and compared. A standard high frequency monolithic transformer was investigated for the integration with the rest of the circuit. Different problems were found as will be discussed. A saturation of the transformer to one side occurred, and a control circuit for this was developed and is discussed. A different approach to transformers, matrix transformers, was investigated for the application in high current, low voltage supplies, such as a compensating supply for a compensated Darlington transistor. From the matrix transformers a new kind of transformer connection style, namely a symmetric transformer, followed. The symmetrical transformer was investigated for the possible use in monolitic transformers, and compared with halfbridge, fullbridge and push-pull transformer configurations. It was decided to proceed further with matrix transformers. A design of a 400A 1.5Vsupply, was done to serve as a compensating supply in a 2000A compensated Darlington transistor switch. The supply was built up and analysed. Different switch configurations were investigated for use as possible transistor switches. The compensated Darlington was considered to be the best. Unexpected switch off problems occurred. These are discussed and an optimum switch off topology is suggested. A 2000A transistor switch was designed and built. Full current could not be reached and results are presented up to 650A.
50
Sithole, Calvin. "Partial discharge measurement in distribution power transformers". Thesis, 2013. http://encore.tut.ac.za/iii/cpro/DigitalItemViewPage.external?sp=1000388.
Testo completoAbstract (sommario):
M. Tech. Electrical Engineering.Discusses the appearance of partial discharge (PDs) is a problem of insulation failure in high voltage equipment used in power plants. As the insulation of equipment has a sensitive zone, therefore the quality of insulation plays an important role in such power equipment. PDs in power transformers are capable of leading to corrosion on solid insulating materials, thereby in the long term, causing a breakdown of the particular operating component. It follows that the real challenge is to identify the most appropriate method for the measurement and/or detection of PDs.