Dissertations / Theses on the topic 'Inductor modelling'
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Wang, Yiren. "Modelling and characterisation of losses in nanocrystalline cores." Thesis, University of Manchester, 2016. https://www.research.manchester.ac.uk/portal/en/theses/modelling-and-characterisation-of-losses-in-nanocrystalline-cores(eddd2c60-7322-4665-9176-b45e53621285).html.
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Increasing the power density of the DC-DC converters requires the size and weight of the magnetic components, such as inductors and transformers, to be reduced. In this thesis, the losses in nanocrystalline inductor cores are characterised and analysed, including the traditional core loss and the gap loss caused by the air gap fringing flux. The loss calculations will form a basis for the design and optimisation of high power inductors for DC-DC converters for EV applications. This thesis first characterises experimentally the core losses in four nanocrystalline cores over a range of operating conditions that are representative of those encontered in typical high power converter applications, including non-sinusoidal waveforms and DC bias conditions. The core losses are assessed by the measured B-H loops and are characterised as a function of DC flux density, showing that for a fixed AC induction level, the losses can vary by almost an order of magnitude as the DC bias increases and the duty ratio moves away from 0.5. The results provide a more complete picture of the core loss variations with both DC and AC magnetisations than is available in manufactures’ data sheets. An electromagnetic finite element (FE) model is used to examine the gap loss that occurs in finely laminated nanocrystalline cores under high frequency operation. The loss is significant in the design example, contributing to almost half of the total inductor loss, and the gap loss is highly concentrated in the region of the air gap. The dependence of the gap loss on key inductor design parameters and operating condtions is also explored. An empirical equation is derived to provide a design-oriented basis for estimating gap losses. Thermal finite element analysis is used to estimate the temperature rise and identify the hot spot in a nanocrystalline inductor encapsulated in an alumimium case. The temperature distribution in the core largely corresponds to the non-uniform distribution of the gap loss. The thermal FEA can also be used to evaluate different thermal management methods to optimise the design for a more compact component. The FE modelling of gap loss and the thermal predictions are validated experimentally on a foil-wound Finemet inductor, showing good agreement between the predictions and measurements under various operating conditions.
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Horsley, Edward Lewis. "Modelling and analysis of radial mode piezoelectric transformers and inductor-less resonant power converters." Thesis, University of Sheffield, 2011. http://etheses.whiterose.ac.uk/12870/.
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Within the electronics industry there is a continual demand for DC-DC power converters that achieve high power density at low cost. Since a piezoelectric transformer (PT) has an electrical equivalent circuit that is similar to several resonant converter topologies, a PT can be used to replace many of the reactive components in these topologies with a single ceramic component, thereby offering potential savings in cost, size, and mass. The first part of this thesis presents a new equivalent circuit model for one of the most promising types of PT, the radial mode Transoner. This model relates the electrical characteristics of the PT to the physical dimensions and material properties. Considerable insight is then gained about how to design these devices to meet a particular set of converter specifications whilst simultaneously maximising PT power density. The second part of this thesis concerns the effect of the rectifier topology on PT power density. Using concepts from material science, together with equivalent circuit models of both the PT and the rectifier topologies, it is shown that a given PT will always achieve a higher thermally limited maximum output power when used in an AC-output topology compared to a DC-output topology. The half-bridge inductor-less PT-based converter topology is particularly attractive because it requires no additional components between the half-bridge and the rectifier. However, it is difficult to achieve zero-voltage-switching (ZVS) without significantly compromising PT power density when using this topology. The third part of this thesis details the development and experimental verification of a new model for the ZVS condition. Using a normalisation scheme and numerical optimisation techniques, the requirements for achieving inductor-less ZVS are accurately quantified for the first time. The impact of these requirements on PT power density is assessed, and design guidelines for maximising PT power density are given.
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Woodward, Lisa. "Fabrication of Novel Suspended Inductors." Thesis, University of Waterloo, 2004. http://hdl.handle.net/10012/870.
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With the rapid growth in the wireless industry there has been increasing demand to make devices with better performance. This means lower power, lower voltage, smaller, and in general more efficient. This has lead to the interest in and necessity for good quality passive components. Good quality passive components make better filters, baluns, voltage controlled oscillators, and matching networks. There has been a lot of work over the last ten years focused on improving the quality of inductors. Typical inductors fabricated on silicon have Q factors of approximately 10. This is because silicon is conductive and therefore acts like a lossy ground plane and develops interfering currents. Improvements that have been attempted include thicker metal layers, thicker dielectric layers, patterned ground shields, as well as using multiple metal layers. These methods, however, still do not improve inductors to the quality of those built on insulating substrates such as glass. The main successful attempt on silicon has been where the inductor coil is released so that it is in the air supported by posts. In some work the inductor coil is raised 50 to 100µm above the underpass by methods like etching or photoresist molding. The suspended inductor approach was applied to an insulating substrate to fabricate and characterize unique suspended inductors and transformers. Inductors were released to have 1µm of air underneath the coil by the use of a release etch. Transformers were made in a similar way except two released layers where used. The top coil, done in plated gold, was released as well as an interconnection layer. Such a small air gap and the transformers with two released metal layers are a couple of the unique features of this thesis work. The devices were characterized up to 20GHz before and after release. An improvement in the peak Q factor (up to 70), as well as in the self-resonance frequency (up to 4GHz higher) was noticed after release. This is expected due to the reduction in parasitics. The results were then compared with simulations and a couple closed form expressions, both of which were able to give a reasonable accuracy. There was also success in getting good high frequency transformers.
Even though some good high-Q inductors were fabricated as part of this thesis, there is still further work that can be done. This includes packaging, integration with capacitors, and further optimization.
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Bartkevičius, Saulius. "The Investigation of High Magnetic Field Long-Life Operation Inductors." Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2009. http://vddb.library.lt/obj/LT-eLABa-0001:E.02~2009~D_20090615_145918-47271.
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The aim of the dissertation is the analysis of high pulsed magnetic field in-ductors in order to determine their electrophysical parameters for non-destructive magnetic field generation. To obtain that effective method to synthe-size inductor geometrical and material models was developed, inductor mathe-matical and computer models created, electrophysical processes during the pulse in windings of various inductors were examined. Finally, retrievals of non-destructive inductor geometrical configurations were performed. Software de-veloped and results gained were successfully used to design new pulsed inductor prototypes.
Dissertation content: introduction, four chapters, general conclusions, list of references and list of author’s publications on the subject of dissertation.
The introduction contains the topicality of the problem, aim of the work, main tasks, scientific novelty, practical value, result approval, defended state-ments and structure description.
Overview of different high magnetic field generation techniques, pulsed in-ductor design, geometry optimization problems and software used for these tasks are the objectives of the first chapter.
The second chapter is dedicated to development of technique for inductor geometrical-material model synthesis, creation of mathematical-computer induc-tor model, definition of long-life operation inductor parameters – their “vitality zone” and design of non-destructive inductor geometries retrieval algorithm.
In the third chapter... [to full text]Disertacijoje nagrinėjami stipraus impulsinio magnetinio lauko induktoriai, kurių ilgaamžiškumas priklauso nuo daugelio jų fizikinių parametrų. Sukūrus induktorių geometrijos sintezės metodiką, sudaryti induktorių matematiniai ir kompiuteriniai modeliai, ištirti impulso metu skirtingų parametrų induktorių ap-vijose vykstantys procesai, atlikta daugkartinio naudojimo induktorių geometrijų paieška. Sukurtas programinis aprūpinimas induktorių skaičiavimams įgalina nustatyti induktorių, tinkamų daugkartiniam impulsiniam magnetiniam laukui generuoti, parametrus. Darbo rezultatai pritaikyti kuriant induktorių prototipus. Disertaciją sudaro įvadas, keturi skyriai, bendrosios išvados, literatūros ir publikacijų disertacijos tema sąrašas. Įvadiniame skyriuje aprašomas problemos aktualumas, formuluojamas dar-bo tikslas ir uždaviniai, pristatomi autoriaus pranešimai ir publikacijos, patei-kiama disertacijos struktūra. Pirmajame skyriuje aptariama stipraus magnetinio lauko reikšmė šiuolaiki-niam mokslui, pristatomi stipraus magnetinio lauko generavimo būdai, analizuo-jami impulsiniai induktoriai, jų kompiuterinių modelių sudarymo problematika, geometrijos optimizavimas. Antrajame skyriuje aprašoma induktorių geometrijos ir medžiagų sudėties sintezės metodika, sukuriamas induktoriaus matematinis-kompiuterinis modelis, apibrėžiama daugkartinio naudojimo induktorių pagrindinių parametrų visuma – „gyvavimo zona“, pateikiamas daugkartinio naudojimo induktorių geometrijų paieškos algoritmas... [toliau žr. visą tekstą]
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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.
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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.
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Bartkevičius, Saulius. "Stiprių magnetinių laukų daugkartinio naudojimo induktorių tyrimas." Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2009. http://vddb.library.lt/obj/LT-eLABa-0001:E.02~2009~D_20090615_145904-52073.
Full textAbstract:
Disertacijoje nagrinėjami stipraus impulsinio magnetinio lauko induktoriai, kurių ilgaamžiškumas priklauso nuo daugelio jų fizikinių parametrų. Sukūrus induktorių geometrijos sintezės metodiką, sudaryti induktorių matematiniai ir kompiuteriniai modeliai, ištirti impulso metu skirtingų parametrų induktorių apvijose vykstantys procesai, atlikta daugkartinio naudojimo induktorių geometrijų paieška. Sukurtas programinis aprūpinimas induktorių skaičiavimams įgalina nustatyti induktorių, tinkamų daugkartiniam impulsiniam magnetiniam laukui generuoti, parametrus. Darbo rezultatai pritaikyti kuriant induktorių prototipus.
Disertaciją sudaro įvadas, keturi skyriai, bendrosios išvados, literatūros ir publikacijų disertacijos tema sąrašas.
Įvadiniame skyriuje aprašomas problemos aktualumas, formuluojamas darbo tikslas ir uždaviniai, pristatomi autoriaus pranešimai ir publikacijos, pateikiama disertacijos struktūra.
Pirmajame skyriuje aptariama stipraus magnetinio lauko reikšmė šiuolaikiniam mokslui, pristatomi stipraus magnetinio lauko generavimo būdai, analizuojami impulsiniai induktoriai, jų kompiuterinių modelių sudarymo problematika, geometrijos optimizavimas.
Antrajame skyriuje aprašoma induktorių geometrijos ir medžiagų sudėties sintezės metodika, sukuriamas induktoriaus matematinis-kompiuterinis modelis, apibrėžiama daugkartinio naudojimo induktorių pagrindinių parametrų visuma – „gyvavimo zona“, pateikiamas daugkartinio naudojimo induktorių geometrijų paieškos algoritmas... [toliau žr. visą tekstą]The aim of the dissertation is the analysis of high pulsed magnetic field inductors in order to determine their electrophysical parameters for non-destructive magnetic field generation. To obtain that effective method to synthesize inductor geometrical and material models was developed, inductor mathematical and computer models created, electrophysical processes during the pulse in windings of various inductors were examined. Finally, retrievals of nondestructive inductor geometrical configurations were performed. Software developed and results gained were successfully used to design new pulsed inductor prototypes. Dissertation content: introduction, four chapters, general conclusions, list of references and list of author’s publications on the subject of dissertation. The introduction contains the topicality of the problem, aim of the work, main tasks, scientific novelty, practical value, result approval, defended statements and structure description. Overview of different high magnetic field generation techniques, pulsed inductor design, geometry optimization problems and software used for these tasks are the objectives of the first chapter. The second chapter is dedicated to development of technique for inductor geometrical-material model synthesis, creation of mathematical-computer inductor model, definition of long-life operation inductor parameters – their “vitality zone” and design of non-destructive inductor geometries retrieval algorithm. In the third chapter... [to full text]
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Göl, Özdemir. "Dynamic modelling of induction machines /." Title page, contents and abstract only, 1993. http://web4.library.adelaide.edu.au/theses/09PH/09phg595.pdf.
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Flack, Timothy John. "Induction motor modelling using finite elements." Thesis, Imperial College London, 1990. http://hdl.handle.net/10044/1/7405.
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Ahmed, M. M. "Modelling of inverter-fed induction machine." Thesis, University of Manchester, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.234246.
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Ardjmandpour, Negah. "Modelling and Inversion of Array Induction tool." Thesis, Imperial College London, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.522875.
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Molavi, Reza. "Modelling and application of spiral inductors in CMOS LC-VCOs." Thesis, University of British Columbia, 2013. http://hdl.handle.net/2429/45377.
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Communication systems are essential components of our everyday lives and they facilitate accessing and using the ever-increasing amounts of data that have surrounded us. The main objective of this research is to present solutions at the device, circuit, and system levels for key passive and active circuit building blocks of communication systems, namely, monolithic passive inductors and inductor-based voltage-controlled oscillators (LC-VCOs). These components are almost ubiquitously used in integrated wireless and wireline communication transceivers, as well as other computing devices. Key contributions of this work are as follows: In the context of monolithic inductors, we have studied different inductor structures such as doubly-stacked inductors, vertical inductors, and coupled-rings. We have developed circuit models to accurately estimate their inductance and quality factor. The proposed analytical expressions provide designers with a reasonable estimate of their circuit performance and layout constraints. The result of proposed analyses is verified by the measurement results of test structures implemented in CMOS technology.
Regarding LC-VCOs, we have studied the effect of large signal oscillations on such VCOs by developing a mathematical model to solve the non-linear differential equation governing the LC tank circuit. The study shows that the VCO frequency and the amplitude of higher order harmonics are functions of circuit parameters such as the C-V characteristics of the varactor and the oscillation amplitude. Also, a low- power technique to boost the output amplitude of push-push VCOs is introduced. Measurement results of a proof-of-concept prototype test chip in 90-nm CMOS confirm the usefulness of the proposed technique.
Finally, at the system level, we present an analytical model to study the effect of coupling between adjacent LC-VCOs closely integrated on the same chip. This is usually the case in high-speed wireline transceivers such as those used in serial links. The proposed model explains the behavior of spurious sidebands as observed in the frequency spectrum of closely-running adjacent links. A redundant frequency mapping scheme is proposed that significantly reduces this coupling effect. Measurement results of a highly packable clock synthesizer in a 65-nm CMOS confirm the validity of the analytical model and the effectiveness of the proposed mapping technique.
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Feyzi, Mohammad Reza. "Thermal modelling of deep bar induction motor at stall /." Contents and summary only, 1997. http://web4.library.adelaide.edu.au/theses/09PH/09phf435.pdf.
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Gaude-Fugarolas, Daniel. "Modelling of transformations during induction hardening and tempering." Thesis, University of Cambridge, 2002. https://www.repository.cam.ac.uk/handle/1810/218539.
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There are many circumstances in industry where steel components are locally heated into the austenite phase field, and then quenched rapidly to produce a hardened region. Induction hardening is one such process used widely in the manufacture of automobile components, in particular to enhance the wear and contact-fatigue resistance of rubbing surfaces.
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Willoughby, Benjamin. "Modelling and simulating a three-phase induction motor." Thesis, Willoughby, Benjamin (2014) Modelling and simulating a three-phase induction motor. Other thesis, Murdoch University, 2014. https://researchrepository.murdoch.edu.au/id/eprint/23525/.
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This project involves modelling and simulating a real three-phase induction motor to determine its transient and steady-state characteristics, such as its torque-speed characteristics, torque-time characteristics, speed-time characteristics and its rotor and stator currents. For the simulation the computer program MATLAB/Simulink was used. The motors equivalent circuit parameters were determined by performing the standard equivalent circuit parameter tests; the DC test, no-load test and the blocked-rotor test. The moment of inertia of the motor was attempted to be determined through power and deceleration tests, although the method proposed in this paper proved to be unsuccessful. The resulting equivalent circuit parameters determined from the suggested tests were highly unlikely for the 0.37 kW motor used, however the MATLAB/Simulink computer program proved to be a suitable program to simulate three-phase induction motors.
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Anjos, Angélica dos. "Comparação de ferramentas para modelamento de indutores na tecnologia CMOS." Universidade de São Paulo, 2007. http://www.teses.usp.br/teses/disponiveis/3/3140/tde-27072007-145121/.
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Duas ferramentas para modelamento de indutores planares, retangulares e integrados e as equações analíticas implementadas em um software, foram estudadas e analisadas, para determinar qual é a mais apropriada, ou seja, aquela que fornece os resultados mais próximos de medidas experimentais, com menor custo, maior velocidade, etc. Indutores planares integrados apresentam limitações severas em seu uso. As duas principais são: o baixo valor do fator de qualidade, que limita o ganho e a banda nos amplificadores e filtros que os utilizam; e a dificuldade no seu modelamento e na determinação dos parâmetros que os caracterizam. Apesar das dificuldades no uso destes dispositivos, eles são aplicados em diversos sistemas, tais como transceptores que operam em rádio freqüências. Nestes sistemas, indutores são necessários e sua integração é essencial para se obter soluções completamente integradas. As ferramentas estudadas para o modelamento de indutores neste trabalho foram: ASITIC e SONNET. As equações analíticas foram implementadas no MATLAB. A comparação entre as ferramentas e as equações foi feita por meio de cinco indutores construídos e medidos. Os indutores foram fabricados em tecnologia CMOS de 0,35 µm com quatro camadas de metal. Para realizar a correta comparação entre os resultados simulados e as medidas elétricas, reduzindo ao máximo a interferência de elementos parasitas (inclusos pelos pads), os indutores foram inseridos em estruturas de teste. Estruturas de caracterização apropriadas foram também projetadas para permitir a eliminação do efeito das estruturas de teste sobre as medidas.Two modeling tools for integrated planar square inductors and one software implementing analytical relations, were studied and analyzed, to determine which is the most appropriate, that is, the tools that will supply the closest results to experimental measurements with, lower costs, higher speed, etc. Integrated planar inductors present severe limitations in their use. The two main limitations are: the low value of the quality factor, that affects the gain and the band of amplifiers and filters where they are used; and the difficulty in modeling and determining of their parameters. Inspire of the difficulties in the use of these devices, they are applied in many systems, such as transceivers that operate in radio frequency. In these systems, inductors are necessary and their integration is essential to obtain completely integrated solutions. In this work the studied tools for inductor modeling were: ASITIC and SONNET. The analytical relations were implementing in MATLAB. The comparisons between the tools were made through five implemented and measured inductors. The inductors were fabricated in a CMOS 0.35 µm technology with four metal layers. In order to carry out the correct comparison between the modeled results and the electric measurements, minimizing the interference of pad parasitic elements, the inductors were inserted within appropriate test structures. Characterization structures were also implemented to allow the elimination of the test structure effects on the measurements.
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Abdi-Jalebi, Ehsan. "Modelling and instrumentation of Brushless Doubly-Fed (induction) Machines." Thesis, University of Cambridge, 2007. https://www.repository.cam.ac.uk/handle/1810/252033.
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Bousbaine, Amar. "An investigation into the thermal modelling of induction motors." Thesis, University of Sheffield, 1993. http://etheses.whiterose.ac.uk/1824/.
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Electric motors are the ubiquitous workhorses of the industry, working a in wide range of conditions and applications. Modern motors, designed to exact ratings using new materials improved manufacturing techniques, are now much smaller but have higher loadings. They are being operated much nearer to the point of overload then ever before. To ensure a satisfactory life span for the motor, temperature rise must be limited to safe values. A lumped parameter thermal model has been developed, which allows rapid and accurate estimation of the temperature distribution in a machine. The lumped parameter thermal model depends on the accurate knowledge of the thermal coefficients and more importantly the loss distribution. Hence the temperature time technique was implemented to investigate the iron loss density distribution. Experimental results are discussed and loss density information throughout the volume of the machine was generated. A novel method of determining the thermal coefficients employed in the heat flow equation was investigated, using the thermal lumped parameter model of a machine. Finally a 2-D finite element method was used to corroborate, or otherwise, the use of the lumped thermal network model.
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Mohamed, Abdulatif Abdusalam. "Modelling and simulation of a cycloconverter induction motor drive." Thesis, De Montfort University, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.391545.
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Williams, J. P. "Mathematical modelling of the dynamic characteristics of induction heating systems." Thesis, Swansea University, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.636635.
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Induction furnaces provide a cost effective, easily controlled means of heating any electrically conductive load by the process of electromagnetic induction. Such furnaces can be more efficient than their fossil fuel equivalents but rising electricity costs have led both the equipment manufacturers and users to demand even higher efficiencies. The research described in this thesis has therefore been undertaken to improve the mathematical analysis with the ultimate aim of developing more rigorous design methodologies. Studies of the mathematical equations describing the energy transfer within the furnace concluded that, due to the complexities involved in predicting magnetic flux distributions, a numerical technique must be used for their solution. The finite element method was identified as the most suitable technique but no package suitable for induction furnaces is commercially available. It was also concluded that full three dimensional analysis would not be viable for most design offices. An existing finite element code (PE2D) used for the analysis of two dimensinal electromagnetic fields was extended to cover the aspects peculiar to induction furnace design. The main development was to enable the solutions of both the magnetic field and the corresponding induced thermal field during transient heating to be obtained. Other developments included such characteristics as non-linear magneto-thermal properties, surface energy losses and optimisation of time step and excitation frequency. The developed models can be applied to two dimensional analysis in a plane normal to conductor coils and also, in some cases, in the plane of a conductor coil. A post-processor was also developed to provide concise graphical output of such information as temperature profiles, magnetic flux distributions and power densities. The models were validated by comparison with analytical examples and by comparison with experimental data obtained with the aid of a fully automated rig capable of three dimensional flux measurements. A future research program has been identified aimed at, firstly, developing the mathematical model to provide a desk top computer design package, and, secondly, extending the experimental work to provide more validation of the code, better material information and supplementary design rules.
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Lei, Ting. "Doubly-fed induction generator wind turbine modelling, control and reliability." Thesis, University of Manchester, 2014. https://www.research.manchester.ac.uk/portal/en/theses/doublyfed-induction-generator-wind-turbine-modelling-control-and-reliability(2ceb051a-a6fb-43e6-be40-a5023dae4bea).html.
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The trend of future wind farms moving further offshore requires much higher reliability for each wind turbine in order to reduce maintenance cost. The drive-train system and power electronic converter system have been identified as critical sub-assemblies that are subject to higher failure rates than the other sub-assemblies in a wind turbine. Modern condition monitoring techniques may help schedule the maintenance and reduce downtime. However, when it comes to offshore wind turbines, it is more crucial to reduce the failure rates (or reduce the stresses) for the wind turbines during operation since the harsh weather and a frequently inaccessible environment will dramatically reduce their availability once a failure happens. This research examines the mechanical, electrical and thermal stresses in the sub-assemblies of a doubly-fed induction generator (DFIG) wind turbine and how to reduce them by improved control strategies. The DFIG control system (the rotor-side and the grid-side converter control) as well as the wind turbine control system are well established. The interactions of these control systems have been investigated. This research examines several further strategies to reduce the mechanical and electrical stresses. The control system's coordination with the protection schemes (crowbar and dc-chopper) during a grid fault is presented as well. An electro-thermal model of the power converter has been developed to integrate with the DFIG wind turbine model, for the evaluation of the thermal stresses under different operating states and control schemes. The main contributions of this thesis are twofold. A first contribution is made by providing all the control loops with well-tuned controllers in a more integrated methodology. The dynamics of these controllers are determined from their mathematical models to minimize the interference between different control-loops and also to reduce the electrical transients. This thesis proposes a coordination strategy for the damping control, pitch control and crowbar protection which significantly reduces the mechanical oscillations. On the other hand, an integrated model of the wind turbine and converter electro-thermal system is established that can illustrate the performance integration with different control strategies.
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Okoro, Ogbonnaya Inya. "Dynamic and thermal modelling of induction machine with non-linear effects." Kassel : Kassel Univ. Press, 2002. http://deposit.d-nb.de/cgi-bin/dokserv?idn=969576749.
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Claassens, Andries Johannes. "Transient modelling of induction motors in a petrochemical plant using Matlab." Thesis, Stellenbosch : Stellenbosch University, 2008. http://hdl.handle.net/10019.1/20432.
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Thesis (MScIng)--University of Stellenbosch, 2008.ENGLISH ABSTRACT: The behaviour of induction motors at a petrochemical plant under transient conditions was investigated with the view to improve plant immunity to voltage fluctuations. The benefits of using a phase-variable induction motor model rather than the simpler d-q models usually employed are investigated. A simplified model of the plant electrical distribution system was derived. Phase variable and d-q induction motor models were implemented as well as a synchronous generator model. Practical considerations precluded the use of commercial software for the simulation of transient conditions and a basic simulation program was developed using Matlab to evaluate the behaviour of the dynamic machine models and distribution system. It was established that the configuration of the installed re-acceleration system can be optimised to reduce the possibility of plant outages as a result of voltage fluctuations. It was found that the use of more detailed induction machine models provide valuable insight into system behaviour and is justified if accurate motor parameters are available or can be estimated. The simplified plant model yielded useful results and enabled the identification of incorrect system data. The investigation showed that Matlab is suitable for the rapid development of a basic transient simulation program that can be used to study the behaviour of different interconnected dynamic machine models.
AFRIKAANSE OPSOMMING: Die gedrag van induksiemotors in 'n petrochemiese aanleg onder oorgangstoestande is ondersoek ten einde die immuniteit van die aanleg vir spanningsfluktuasies te verbeter. Die voordele van die gebruik van 'n fase-veranderlike induksiemotor model eerder as die eenvoudiger d-q modelle wat normaalweg gebruik word is ondersoek. 'n Vereenvoudigde model van die aanleg se elektriese distribusiestelsel is afgelei. Faseveranderlike en d-q induksiemotor modelle is geimplementeer sowel as 'n sinkroongenerator model. Praktiese oorwegings het die gebruik van kommersiële programmatuur vir die simulasie van oorgangstoestande verhoed en 'n basiese program is in Matlab ontwikkel om die gedrag dinamiese masjienmodelle en die distribusiestelsel te evalueer. Daar is vasgestel dat die konfigurasie van die geinstalleerde herversnellerstelsel geoptimeer kan word om die moontlikheid van aanleg onderbrekings as gevolg van spanningsfluktuasies te verminder. Daar is gevind dat die gebruik van meer gedetaileerde induksiemasjien modelle waardevolle insig in die gedrag van die stelsel lewer en geregverdig is indien akkurate motorparameters beskikbaar is of afgeskat kan word. Die vereenvoudigde model van die aanleg het bruikbare resultate gelewer en die het die identifikasie van foutiewe stelseldata moontlik gemaak. Die ondersoek het getoon dat Matlab geskik is vir die snelle ontwikkeling van 'n basiese oorgangsimulasie program wat gebruik kan word om die gedrag van verskillende gekoppelde dinamiese masjienemodelle te bestudeer.
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Fahmi, Nagi R. "Modelling of induction motors for system faults and transient stability studies." Thesis, Aston University, 1986. http://publications.aston.ac.uk/8049/.
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The research carried out in this thesis was mainly concerned with the effects of large induction motors and their transient performance in power systems. Computer packages using the three phase co-ordinate frame of reference were developed to simulate the induction motor transient performance. A technique using matrix algebra was developed to allow extension of the three phase co-ordinate method to analyse asymmetrical and symmetrical faults on both sides of the three phase delta-star transformer which is usually required when connecting large induction motors to the supply system. System simulation, applying these two techniques, was used to study the transient stability of a power system. The response of a typical system, loaded with a group of large induction motors, two three-phase delta-star transformers, a synchronous generator and an infinite system was analysed. The computer software developed to study this system has the advantage that different types of fault at different locations can be studied by simple changes in input data. The research also involved investigating the possibility of using different integrating routines such as Runge-Kutta-Gill, RungeKutta-Fehlberg and the Predictor-Corrector methods. The investigation enables the reduction of computation time, which is necessary when solving the induction motor equations expressed in terms of the three phase variables. The outcome of this investigation was utilised in analysing an introductory model (containing only minimal control action) of an isolated system having a significant induction motor load compared to the size of the generator energising the system.
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Souley, Madougou Abdoul Majid. "Contribution à l'étude et à la commande d'un système de chauffage par induction polyphasé." Phd thesis, Toulouse, INPT, 2011. http://oatao.univ-toulouse.fr/18601/1/souley_madougou_partie_1_sur_2_2.pdf.
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Le chauffage par induction est un procédé qui consiste à plonger un matériau conducteur d’électricité dans un champ magnétique variable, ayant ainsi pour effet, la création de FEM donc de courants de Foucault dont la circulation élève la température du matériau par effet Joule. Ce mode de chauffage est déjà implanté industriellement dans de nombreux secteurs parmi lesquels des fonderies et s’intègre bien dans les processus de traitement des matériaux en raison de ses divers avantages. Il permet notamment, l’atteinte de densités de puissances très élevées dont la distribution peut être contrôlée. Il est ainsi possible d’obtenir des chauffages localisés ou de l’ensemble du matériau suivant le traitement désiré. Cette souplesse du contrôle des profils de chauffe et une forte puissance de chauffe requièrent traditionnellement l’usage de systèmes comportant plusieurs bobines. Leur caractérisation aussi précise que possible et le contrôle des courants des inducteurs sont nécessaires. L’étude présentée ici recense dans un premier temps, les quelques solutions existantes dont la puissance est réglée en déplaçant des culasses et/ou des écrans magnétiques, permettant de mieux répartir les champs magnétiques produits, afin de disposer du profil de chauffe souhaité mais pour une faible gamme de tôles. Les rares solutions qui s’intéressent au contrôle électrique sont orientés vers du chauffage monophasé. La transposition directe de ces commandes aux cas multi-bobines ne suffit pas à résoudre le problème dans son intégralité car les inducteurs se perturbent mutuellement. Nous nous sommes donc orientés vers une solution ambitieuse qui permet de s’affranchir de pièces mobiles et rend le système plus fiable, plus précis et lui confère plus de souplesse pour s’adapter à différents profils de chauffe et différentes largeurs de matériaux. Cette solution se base sur une méthode qui consiste à contrôler les profils de chauffe par la seule action sur les courants d’alimentation des inducteurs tout en maitrisant les échanges d’énergie entre les inducteurs fortement couplés. Cette solution est appliquée sur un prototype construit par EDF. Dans un premier temps, nous avons modélisé le système dans son ensemble tant du point de vue électrique et magnétique que thermique, afin de disposer d’un modèle global simplifié qui permet de mieux en étudier le comportement. Une procédure d’optimisation permet de générer les amplitudes et les phases des courants inducteurs pour différents profils de chauffe. Après une étape d’identification paramétrique, nous avons défini et implanté un modèle simplifié dans le logiciel PSim, qui nous fournit des délais de simulation relativement courts. Les résultats obtenus ont été ensuite comparés à des expérimentations en boucle ouverte tout d’abord, qui nous ont conduits à une étude de sensibilité des grandeurs du système aux variations paramétriques. Il nous a été possible de commander le système grâce à un FPGA dans lequel nous avons implanté une commande numérique pour le contrôle des courants des inducteurs en vue du chauffage en statique d’un disque de tôle pour différents profils de consigne. Nous avons ensuite amélioré nos modèles dans différentes directions, par la prise en compte du rayonnement et de la conduction thermique, en les transposant à un système plus complexe à six phases et avec une prise en compte du défilé des matériaux. L’extension du principe de l’induction multi-bobines de 3 à 6 phases a révélé de fortes perturbations harmoniques des courants des inducteurs. Notre travail a permis de maîtriser les harmoniques en choisissant judicieusement les angles de commande et de caractériser les pertes dans les onduleurs.
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Matandirotya, Electdom. "Measurement and modelling of geomagnetically induced currents (GIC) in power lines." Thesis, Cape Peninsula University of Technology, 2016. http://hdl.handle.net/20.500.11838/2459.
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Thesis (DTech (Electrical Engineering))--Cape Peninsula University of Technology, 2016.Geomagnetically induced currents (GIC) are currents induced in ground-based conductor networks in the Earth's surface. The GIC are driven by an electric eld induced by geomagnetic variations which are a result of time-varying magnetospheric-ionospheric currents during adverse space weather events. Several studies have shown that there is a likelihood of technological damage (the power grid) in the mid- and low-latitude regions that could be linked to GIC during some geomagnetic storms over the past solar cycles. The effects of GIC in the power system can range from temporary damage (e.g. protective relay tripping) to permanent damage (thermal transformer damage). Measurements of GIC in most substations are done on the neutral-to-ground connections of transformers using Hall-effect transducers. However, there is a need to understand the characteristics of GIC in the power lines connected to these transformers. Direct measurements of GIC in the power lines are not feasible due to the low frequencies of these currents which make current measurements using current transformers (CT) impractical. This thesis discusses two techniques that can be employed to enhance understanding GIC characteristics in mid-latitude regions. The techniques involve the measurement of GIC in a power line using differential magnetometer measurements and modelling GIC using the finite element method. Low frequency magnetometers are used to measure magnetic felds in the vicinity of the power lines and the GIC is inferred using the Biot-Savart law. A finite element model, using COMSOL-Multiphysics, is used to calculate GIC with the measured magnetic field and a realistic Earth conductivity profile as inputs. The finite element model is used for the computation of electric field associated with GIC modelling.
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Potter, Benjamin Alexander. "Investigation into the input impedance of induction machines using measurement and modelling." Thesis, University of Reading, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.501347.
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This thesis presents material that aims to further the understanding of the variation of the input impedance of induction machines with frequency. The input impedance is shown to be of importance when predicting or mitigating the effects of harmonics in machines that are driven by an inverter. The main body of this thesis consists of experimental results from a study that characterises the input impedance of thirteen different induction machines of various sizes and with different numbers of poles.
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Wyllie, Peter Bruce. "Electrothermal modelling for doubly fed induction generator converter reliability in wind power." Thesis, Durham University, 2014. http://etheses.dur.ac.uk/10902/.
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Increased reliance upon renewable energy sources, chiefly wind, places a growing emphasis on the reliability of the technology used in Wind Turbines. The current Wind Turbine fleet is dominated by the Doubly Fed Induction Machine WT, which utilises a partially rated power electronic converter to vary the speed of the rotor and thus ensure the maximum energy capture available from the wind. This converter is associated with a significant percentage of WT failures. This thesis examines the low frequency temperature cycling occurring in one half of the back to back converter which results in a high failure rate of the rotor side converter as compared to the grid side converter. To this end a MATLAB/PLECS model was constructed to demonstrate the temperature cycling occurring in a 2.5MW DFIG WT. Lifetime of the semiconductor devices was extrapolated. An adaptation to the standard Maximum Power Point Tracking control method was suggested in which the lowest operating frequencies (less than 2.33Hz) were avoided. In doing so, lifetime was observed to increase at a minor cost to energy yield from the WT.
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Andersen, Peter Scavenius. "Modelling and analysis of asynchronous and synchronous torques in split-phase induction machines." Thesis, University of Glasgow, 2008. http://theses.gla.ac.uk/82/.
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In this thesis, the nature of asynchronous and synchronous torques in a split-phase induction machine is investigated and quantified. The equivalent circuit for this type of machine is derived using the rotating field theory. It is extended to include harmonic effects. Using this model, winding harmonics and permeance harmonics may be calculated independently of each other so that the model can be used to analyse asynchronous torques from winding harmonics as well as synchronous torques from permeance harmonics. These are calculated separately. The asynchronous torques appear as perturbations in the steady-state torque-speed curve while the synchronous torques only appear at specific speeds. The synchronous torques are superimposed onto the torque-speed curves to model both effects together. The model predictions are compared against test results using purpose-built experimental machines together with production machines. These have varying rotor bar number and skew. Different methods are used to assess the synchronous torques. It is found that measuring synchronous locking torque is not a straightforward matter; however, reasonable agreement is found between calculation and measurement. The work highlights the need for the correct choice of stator and rotor slot numbers together with the effect skew has on reducing the synchronous and asynchronous locking torques.
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MacDonald, Kenneth J. "Parallel processing methods applied to two and three dimensional geo-electromagnetic induction modelling." Thesis, University of Edinburgh, 1996. http://hdl.handle.net/1842/11078.
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Two existing finite difference algorithms for solving the forward modelling problem of geoelectromagnetic induction have been recoded to take advantage of high performance massively parallel SIMD (single instruction multiple data) computer architectures. Poll's solves the two scalar polarised fields in the two dimensional (2D) problem, and the other from Pu solves for all three components of the magnetic field in three dimensional (3D) structures. Both models apply integral boundary conditions at the top and bottom of the grid to limit total mesh size. The 3D model introduces a thin sheet at the top of the model to describe near surface features. An efficient data parallel algorithm ensures the evaluation of the integrals maintains a high ratio of processor utilisation on the parallel hardware. Data parallel versions of the point Jacobian, Gauss-Seidel and successive overrelaxation iterative solvers have been developed. The latter two require two level black-white ordering, which to equalise the processor load balance, has been implemented in both a horizontally banded and chequer boarded remapping of grid nodes. The 2D model was also developed to form a task farm, whereby the solution for each period is performed on one of a cluster of workstations. These solutions are independent of each other, so are executed simultaneously on however many workstations are available at the time. Modern workstations, coupled with the original 2D Gauss-Jordan solver, are faster than the SIMD computers for all but the largest grid sizes. However, the 3D code certainly benefited from the parallel processing for any but the smallest models. A new automatic meshing algorithm, which stretches a predefined number of grid points over the conductivity structure, has also been developed. In part, this was to control the mesh sizes and hence load balancing on the SIMD computers, but investigations into grid spacing for 2D models show that severely restricting the number of grid points results in a much faster estimated solution.
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Johnson, Kim Henry Silvanus. "Glucose oxidase induction and the modelling of gluconic acid production using Aspergillus niger." Master's thesis, University of Cape Town, 1995. http://hdl.handle.net/11427/21517.
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The aim of this project is to establish and understand the production of glucose oxidase and gluconic acid using the Aspergillus niger bioprocess and predict its response to operating conditions. Glucose oxidase and gluconic acid are produced by a wide range of microbes and have a variety of applications. In this study Aspergillus niger was chosen as the microorganism as it has the "generally accepted as safe" (gras) status in the U.S.A. It is also the major industrial producer. Glucose oxidase catalyses the conversion of glucose, oxygen and water to hydrogen peroxide and gluconic acid. This enzyme is used as a glucose and oxygen scavenger in the food industry and as a diagnostic tool in medicine for glucose determination. Gluconic acid is an organic acid used as a sequestering agent with a broad spectrum of applications. The world market for gluconic acid and its various salts was 45 000 metric tonnes in 1985 (Bigelis cited by Markwell et al. 1989). Gluconic acid and its derivatives can be produced using three technologies: electrolysis, mild chemical oxidation and bioprocess. The first two technologies have not been proven to be comnercially viable. The bioprocess offers diversity of feed and produces other products such as glucose oxidase. Literature has shown that the production of gluconic acid involves two kinetic areas. Firstly, the glucose oxidase enzyme must be induced. Secondly, glucose is converted to gluconic acid by the enzyme glucose oxidase. The factors affecting the kinetics associated with the induction of glucose oxidase have only been described qualitatively. Glucose, oxygen and pH have been shown to affect the induction of glucose oxidase. The effect of pH has been studied by Roukas and Harvey (1989) who found that induction, is maximal at a pH of between 5 and 6. The effect of glucose and oxygen have not been quantified. The kinetics of glucose oxidase conversion of glucose to gluconic acid have been well described by Atkinson and Lester (1974).
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Sousounis, Marios Charilaos. "Electro-mechanical modelling of tidal arrays." Thesis, University of Edinburgh, 2018. http://hdl.handle.net/1842/31089.
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The aim of this study is to present, compare and improve the options of power transmission for tidal current arrays. The potential to generate low or zero carbon power from the world’s tides is increasing as technology moves forward. The technically available tidal current energy resource, the resource that can be captured using existing technology, in the United Kingdom can supply a significant amount of the UK electricity demand. Even though tidal current devices have similarities to offshore wind turbines in many aspects, a number of characteristics differentiate the approach needed regarding power transmission and drive-train design. Some of these characteristics are: predictable direction and speed of the tidal current, predetermined available area in a tidal channel, less swept area due higher density of water, continuous underwater operation and smaller distances to shore. This thesis is based on the hypothesis that tidal current energy can be harnessed using today’s technology in an efficient manner. Technology progression never stops and as new materials and methods become available the cost of utilising tidal current energy will drop in the years to come. However, the research question that has to be asked is whether using today’s technology tidal arrays can be an alternative source of electrical power. In order to respond to this research question electromechanical models of tidal current devices have been developed in detail, from resource to the grid connection, using mathematical linear and non-linear programming in MATLAB/Simulink. The tidal models developed include the tidal resource, the tidal turbine with pitch control, geared induction and synchronous generators, the power electronics with the generator controller, the grid side controller, the cables for power transmission, the filters and the grid connection. All the modelling aspects of this study are presented in Chapter 3. Single tidal current devices were compared using different generator technologies, squirrel cage induction generator or permanent magnet synchronous generator, and different location of the power converters, in the nacelle near the generator or many kilometres apart from the generator. Regarding the generator technology, results showed that even though differences are minor, the permanent magnet synchronous generators are more efficient. Regarding the location of the power converters results showed that positioning the power converters in the nacelle always yields fewer electrical losses but component accessibility is minimised due to the underwater operation of the tidal current device. A key focus aspect of the study is the power transmission option with onshore converters which is presented in detail. Using this concept it is possible to generate electricity from tidal current devices but at the same time keep the highest possible system reliability despite the continuous underwater operation. This concept has been used in the first demonstration tidal current arrays developed by Andritz Hydro Hammerfest. What is more, data provided by Andritz Hydro Hammerfest were utilised in order to validate the simulation models. In this study a step forward is taken regarding the concept of keeping the converter dry and controlling the tidal current generator from afar. An algorithm is developed to design power harmonic filters for systems that use long distance controls. Power harmonic filters allow the long distance control system to operate reliably under all conditions but generate significant electrical losses. The power harmonic filter design algorithm presented in this thesis estimates the exact filter parameters so that the filter ensures maximum system reliability and generate minimum possible losses. In addition tidal array topologies using this concept are developed. The final part of this thesis compares a number of different tidal array topologies based on resource to grid efficiency and component accessibility for maintenance. Results showed that when tidal current devices are clustered per four turbines on offshore platforms it is efficient to use as many clusters as possible connected to a single cable whose both ends are connected to the grid. Locating the power converters in the nacelle yields fewer electrical losses compared to locating the power converters on the offshore platform. However, the difference is minimised because the distance between the tidal current device and the offshore platform is the least possible. Having the power converters on an offshore platform is beneficial in terms of accessibility for maintenance and operation because they are not underwater. The results and the methodology from this thesis can be extended to other offshore renewable energy systems such as the wind and wave. In addition, this study can be used as a stepping stone for decision making by tidal current developers.
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Okoro, Ogbonnaya Inya [Verfasser]. "Dynamic and thermal modelling of induction machine with non-linear effects / Ogbonnaya Inya Okoro." Kassel : Kassel Univ. Press, 2002. http://d-nb.info/969576749/34.
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Mei, Francoise. "Small-Signal Modelling and Analysis of Doubly-Fed Induction Generators in Wind Power Applications." Thesis, Imperial College London, 2008. http://hdl.handle.net/10044/1/4249.
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The worldwide demand for more diverse and greener energy supply has had a significant impact on the development of wind energy in the last decades. From 2 GW in 1990, the global installed capacity has now reached about 100 GW and is estimated to grow to 1000 GW by 2025. As wind power penetration increases, it is important to investigate its effect on the power system. Among the various technologies available for wind energy conversion, the doubly-fed induction generator (DFIG) is one of the preferred solutions because it offers the advantages of reduced mechanical stress and optimised power capture thanks to variable speed operation. This work presents the small-signal modelling and analysis of the DFIG for power system stability studies. This thesis starts by reviewing the mathematical models of wind turbines with DFIG convenient for power system studies. Different approaches proposed in the literature for the modelling of the turbine, drive-train, generator, rotor converter and external power system are discussed. It is shown that the flexibility of the drive train should be represented by a two-mass model in the presence of a gearbox. In the analysis part, the steady-state behaviour of the DFIG is examined. Comparison is made with the conventional synchronous generators (SG) and squirrel-cage induction generators to highlight the differences between the machines. The initialisation of the DFIG dynamic variables and other operating quantities is then discussed. Various methods are briefly reviewed and a step-by-step procedure is suggested to avoid the iterative computations in initial condition mentioned in the literature. The dynamical behaviour of the DFIG is studied with eigenvalue analysis. Modal analysis is performed for both open-loop and closed-loop situations. The effect of parameters and operating point variations on small signal stability is observed. For the open-loop DFIG, conditions on machine parameters are obtained to ensure stability of the system. For the closed-loop DFIG, it is shown that the generator electrical transients may be neglected once the converter controls are properly tuned. A tuning procedure is proposed and conditions on proportional gains are obtained for stable electrical dynamics. Finally, small-signal analysis of a multi-machine system with both SG and DFIG is performed. It is shown that there is no common mode to the two types of generators. The result confirms that the DFIG does not introduce negative damping to the system, however it is also shown that the overall effect of the DFIG on the power system stability depends on several structural factors and a general statement as to whether it improves or detriorates the oscillatory stability of a system can not be made.
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Malik, Naveed ur Rehman. "Modelling, Analysis, and Control Aspects of a Rotating Power Electronic Brushless Doubly-Fed Induction Generator." Doctoral thesis, KTH, Elektrisk energiomvandling, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-174349.
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This thesis deals with the modeling, analysis and control of a novel brushlessgenerator for wind power application. The generator is named as rotatingpower electronic brushless doubly-fed induction machine/generator (RPEBDFIM/G). A great advantage of the RPE-BDFIG is that the slip power recoveryis realized in a brushless manner. This is achieved by introducing an additionalmachine termed as exciter together with the rotating power electronicconverters, which are mounted on the shaft of a DFIG. It is shown that theexciter recovers the slip power in a mechanical manner, and delivers it backto the grid. As a result, slip rings and carbon brushes can be eliminated,increasing the robustness of the system, and reducing the maintenance costsand down-time of the turbine. To begin with, the dynamic model of the RPE-BDFIG is developed andanalyzed. Using the dynamic model, the working principle of the generatoris understood and its operation explained. The analysis is carried out atspeeds, ±20% around the synchronous speed of the generator. Moreover, thedynamics of the generator due to external load-torque disturbances are investigated.Additionally, the steady-state model is also derived and analyzed forthe machine, when operating in motor mode. As a next step, the closed-loop control of the generator is considered indetail. The power and speed control of the two machines of the generator andthe dc-link voltage control is designed using internal model control (IMC)principles. It is found that it is possible to maintain the stability of thegenerator against load-torque disturbances from the turbine and the exciter,at the same time maintain a constant dc-link voltage of the rotor converter.The closed-loop control is also implemented and the operation of the generatorwith the control theory is confirmed through experiments.In the third part of the thesis, the impact of grid faults on the behaviourof the generator is investigated. The operation of the generator and its responseis studied during symmetrical and unsymmetrical faults. An approachto successful ride through of the symmetrical faults is presented, using passiveresistive network (PRN). Moreover, in order to limit the electrical and mechanicaloscillations in the generator during unsymmetrical faults, the dualvector control (DVC) is implemented. It is found that DVC to a certain extentcan be used to safeguard the converter against large oscillations in rotorcurrents. Finally, for completeness of the thesis, a preliminary physical design ofthe rotating power electronic converter has been done in a finite elementsoftware called ANSYS. The thermal footprint and the cooling capability,with estimates of the heatsink and fan sizes, are presented. Besides, another variant of a rotating electronic induction machine whichis based on the Lindmark concept and operating in a single-fed mode is also investigated. It’s steady-state model is developed and verified through experiments.QC 20151006
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Anand, Vivek. "Modelling and Control of a Dual Sided Linear Induction Motor for a scaled Hyperloop Pod." Thesis, KTH, Fordonsdynamik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-285801.
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The electrification era has been marked up by an increase in volume of electric vehicles which are directly or indirectly powered by electricity. Railways, roadways and airways are being electrified as we speak at their own respective rate. In addition to that upcoming concepts for transport solution such as hyperloop also described as the fifth mode of transportation will be electrified. The current thesis work is based on developing the model and control of the propulsion system of a scaled Hyperloop pod designed by student team KTH Hyperloop representing KTH. The team competes in Hyperloop competition organized by Spacex and the goal is to achieve the highest possible speed in a given distance and track designed by SpaceX. In order to achieve the goal of being the fastest, the scaled pod uses a Double Sided Linear Induction Motor (DSLIM) as mentioned in the subsequent chapter. The motor modelling is done on Simulink and is similar to a rotary induction motor (RIM). However the presence of end effect in DSLIM makes it different from RIM and has been discussed subsequently. The control strategy uses a synchronous frame PI control for the current control and sensor based speed control for controlling the speed of the pod.The speed control output is a reference current which is used as an input to the current controller which finally gives voltage as the control output. The corresponding bandwidth for the various loops have been calculated based on motor parameters as discussed in the method section. The validation of the motor model and the corresponding controller has been discussed in the result section, where the accuracy of the controller for the designed modelled is discussed.Elektrifieringstiden har präglats av en ökning i volym av elfordon som direkt eller indirekt drivs med el. Järnvägar, vägar och luftvägar elektrifieras just nu med deras respektive takt. Utöver det kommer kommande koncept för transportlösning som hyperloop som också beskrivs som det femte transportsättet att elektrifieras. Detta examensarbete bygger på att utveckla modellen och regleringen av framdrivningssystemet för en nedskalad Hyperloop-pod utvecklad av studentteamet KTH Hyperloop som representerar KTH. Teamet tävlar i Hyperloop-tävlingen organiserad av SpaceX och målet är att uppnå högsta möjliga hastighet på ett visst avstånd och spår framtaget av SpaceX. För att uppnå målet om att vara snabbast använder den nedskalade podden en dubbelsidig elektrisk linjär induktionsmotor (DSLIM) som nämns i det följande kapitlet. Den elektriska motormodelleringen görs i Simulink och liknar en roterande induktionsmotor(RIM). Men närvaron av ’end effect’ i DSLIM gör den annorlunda än RIM och har diskuterats därefter. Styrstrategin använder en synkron ram-PI-styrning för strömstyrning och sensorbaserad hastighetsreglering för att styra hastigheten på podden. Varvtalsstyrningsutgången är en referensström som används som en ingång till den nuvarande styrenheten som slutligen ger spänning som slutling styrning. Motsvarande bandbredd för de olika slingorna har beräknats baserat på elektriska motorparametrar som diskuterats i metodavsnittet.Valideringen av elmotormodellen och motsvarande styrenhet har diskuterats i resultatsektionen, där noggrannheten hos styrenheten för den konstruerade modellerna diskuteras.
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Bui, Myvan. "Induction in Fluid Intelligence: Knowledge, novelty, learning and proactive interference." University of Sydney, 2010. http://hdl.handle.net/2123/6293.
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Doctor of Philosophy(PhD)The main aim of this thesis was to examine whether learning processes occur in fluid intelligence (Gf) tasks, whether it is essential for them to occur for induction to take place and whether they contribute to individual differences in performance. In mainstream differential research, Gf is conceptualised as a factor important in induction tasks that are considered novel and context-free (Cattell, 1963, 1987). Thus, performance has typically been assumed to be uninfluenced by previous acquisitions of knowledge structures. Sources of individual differences in Gf task performance have been attributed to working memory capacity (WMC), particularly individual differences in the ability to combat proactive interference. In contrast, the cognitive reasoning literature associates induction with the use of prior conceptual knowledge. A middle-ground position is that Gf tasks may require learning to occur across the task, which would draw upon WMC. That is, individual differences in Gf task performance may be due to knowledge learnt across the task, rather than knowledge brought to the task. Gf items have traditionally been presented in easy-to-hard order but easier items may unintentionally provide learning opportunity for harder items. This would contradict both classic and modern test theories which make the assumption that items within a task are independent of each other. The learning hypothesis was explored in the current work along with the issue of whether it is possible to reliably solve complex Gf items without some relevant, prior knowledge. Also, the distinction between within-item induction and across-item learning was investigated, along with the relationship between across-item learning and proactive interference. An experimental-differential approach was used to manipulate learning opportunity within Gf tasks in four experiments. The first experiment examined whether learning takes place in Raven’s Advanced Progressive Matrices (Raven, 1962) and if so, to what extent this learning is a source of individual differences. Specifically, whether rule learning within the task is necessary for abstraction to take place and whether those of higher Gf ability learn faster than those of lower Gf ability. The next three experiments examined the distinction between knowledge that may be brought to the task, learning that occurs across multiple items in the task and induction within a single item that may be independent of any prior knowledge including knowledge learnt across the task. The effect of proactive interference as a consequence of learning and knowledge was also investigated. The experiments examined which of these are relevant to general performance (i.e., common to everyone) and which contribute to individual differences. Learning-opportunity was manipulated in a task from the cognitive reasoning literature – the Modified Sweller and Gee (MSG) Task. Traditional Series Completion tasks were used as Gf markers and data analyses employed Hierarchical Linear Modelling (HLM). The advantage of the MSG Task is that it has qualities typical of Gf tasks but unlike conventional Gf tasks, it is able to assess within-item induction in isolation from any potential influences from across-item learning. This is because it involves multiple attempts within each item with feedback, allowing single items to be administered reliably. When across-item learning opportunity is absent, the MSG Task is able to provide an estimate of participants’ within-item induction success through the number of attempts they need within a single item. The amount participants learn across items can be approximated by comparing performance on items preceded by learning opportunity (i.e., easier items with similar rule-types), with items not preceded by learning opportunity. Lastly, the effects of proactive interference can be evaluated by comparing performance on items preceded by interference (i.e., items with different rule-types) with those that are not preceded by interference. Overall, it was found that with no learning opportunity leading up to novel items (to provide relevant prior knowledge), solution was nearly impossible for all participants. When learning opportunity was provided, all participants were able to greatly improve their performance but those of higher Gf improved more. It was concluded that while Gf tasks appear visually novel, they must contain a combination of familiar elements in earlier items (which make use of knowledge that participants bring to the task) and novel elements in later items (which require the use of knowledge that must be learnt from earlier items); and those of higher Gf perform better on Gf tasks, at least partly because they are able to benefit more from the learning opportunity provided by earlier items. It was found that proactive interference affects all participants when they learn from prior items. However, insufficient evidence was found to suggest that the ability to combat proactive interference contributes to individual differences in performance.
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Zafar, Jawwad. "Winding short-circuit fault modelling and detection in doubly-fed induction generator based wind turbine systems." Doctoral thesis, Universite Libre de Bruxelles, 2011. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209854.
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AbstractThis thesis deals with the operation of and winding short-circuit fault detection in a Doubly-Fed Induction Generator (DFIG) based Wind Turbine Generator System (WTGS). Both the faulted and faultless condition of operation has been studied, where the focus is on the electrical part of the system. The modelled electrical system is first simulated and the developed control system is then validated on a test bench. The test-bench component dimensioning is also discussed.
The faultless condition deals with the start-up and power production mode of operation. Control design based on the Proportional Integral (PI) control technique has been compared for power and torque control strategies against the Linear Quadratic Gaussian (LQG) control technique, at different operating points through the variable-speed region of WTGS operation following the maximum power curve of the system. It was found that the torque control strategy offered less degradation in performance for both the control techniques at operating points different for the one for which the control system was tuned. The start-up procedure of the DFIG based WTGS has been clarified and simplified. The phase difference between the stator and the grid voltage, which occurs due to the arbitrary rotor position when the rotor current control is activated, is minimized by using a sample-and-hold technique which eliminates the requirement of designing an additional controller. This method has been validated both in simulation and experiments.
The faulted condition of operation deals with the turn-turn short-circuit fault in the phase winding of the generator. The model of the generator, implemented using the winding-function approach, allows the fault to be created online both in a stator and a rotor phase. It has been demonstrated that the magnitude of the current harmonics, used extensively in literature for the Machine Current Signature Analysis (MCSA) technique for winding short-circuit fault detection, is very different when the location of the fault is changed to another coil within the phase winding. This makes the decision on the threshold selection for alarm generation difficult. Furthermore, the control system attenuates the current harmonics by an order of magnitude. This attenuation property is also demonstrated through experiments. The attention is then shifted to the negative-sequence current component, resulting from the winding unbalance, as a possible fault residual. Its suitability is tested in the presence of noise for scenarios with different fault locations, fault severity in terms of the number of shorted-turns and grid voltage unbalance. It is found that due to the presence of a control system the magnitude of the negative-sequence current, resulting from the fault, remains almost the same for all fault locations and fault severity. Thus, it was deemed more suitable as a fault residual. In order to obtain a fast detection method, the Cumulative Sum (CUSUM) algorithm was used. The test function is compared against a threshold, determined on the basis of expected residual magnitude and the time selected for detection, to generate an alarm. The validation is carried out with noise characteristics different from the ones used during the design and it is shown that the voltage unbalance alone is not able to trigger a false alarm. In all the scenarios considered, the detection was achieved within 40 ms despite the presence of measurement filters.
Doctorat en Sciences de l'ingénieur
info:eu-repo/semantics/nonPublished
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Elgwel, Abdulbast Mohamed. "Aspect independent detection and discrimination of concealed metal objects by electromagnetic pulse induction : a modelling approach." Thesis, Manchester Metropolitan University, 2013. http://e-space.mmu.ac.uk/315698/.
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The work presented in this thesis describes the research, modelling and experimentation which were carried out so as to explore the use of electromagnetic pulse induction for the detection of nearby or on-body threat items such as handguns and knives. Commercially available finite difference time domain electromagnetic solver software, Vector Fields, was used to simulate the interaction of a low frequency electromagnetic pulse with different metal objects. The ability to discriminate between objects is based on the lifetime of the induced currents in the object, typically around 100 (μs). Lifetimes are different for a different objects, whether they are weapons or benign objects. For example hand grenades, knives, and handguns are clearly threat objects whereas a wrist watch, mobile phone and keys are considered benign. Electromagnetic pulse Induction (EMI) relies on generating a time-changing but spatially uniform magnetic field, which penetrates and encompasses a concealed metallic object. The temporally changing magnetic field induces eddy currents in the conducting object, which subsequently decay by dissipative (i.e. resistive) losses. These currents decay exponentially with time and exhibit a characteristic time constant (lifetime) which depends only upon the size, shape and material composition of the object, whilst the orientation of the object is irrelevant. This aspect independence of temporal current decay rates forms the basis of a potential object detection and identification system. This thesis investigates the possibility of detecting, resolving and identifying multiple objects if they are close together, for example located on an individual. The mathematical analysis used for the investigation implements the generalised pencil of function (GPOF) method. The GPOF algorithm decomposes the signal into a discrete set of complex frequency components; providing the capability to obtain the time constants from data. It was possible to effectively count and identify multiple metallic objects carried in close proximity providing that the objects do not have very similar time constants. The simulation results, which show that multiple objects can be detected, resolved and identified by means of their time constants even when they are close together, are presented.
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Lima, da Silva Marcio. "Modélisation de la vidange d'une fonte verrière chauffée par induction." Thesis, Grenoble, 2014. http://www.theses.fr/2014GRENI015/document.
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Le présent travail de thèse s'inscrit dans le cadre de la mise au point d'un nouveau procédé de fusion d'oxydes dans un four chauffé par induction. Le procédé étudié met en jeu des fortes interactions entre des phénomènes électromagnétique, thermique et hydrodynamique dans un milieu fluide aux propriétés physiques fortement dépendantes de la température. L'objectif de la thèse est de modéliser le procédé en couplant étroitement le chauffage par effet Joule, le brassage mécanique et la vidange du four. La modélisation de l'évolution temporelle de l'interface entre le verre et l'air lors de vidange du creuset froid a été réalisée. S'agissant de la méthodologie, nous avons choisi de coupler deux logiciels : Flux® pour le calcul électromagnétique et Fluent® pour la thermo-hydraulique. L'évolution de la surface libre a été traitée par la méthode multiphasique « Volume-Of-Fluid – VOF », et l'agitation mécanique par les modèles « Moving Reference Frame » et « Sliding Mesh ». Nous avons d'abord considéré la vidange sans agitation mécanique d'une cuve remplie d'une huile silicone de haute viscosité. Ce modèle initial prend en compte des études de similitude hydraulique entre l'huile silicone et le verre. Puis nous avons superposé l'écoulement forcé crée par un agitateur mécanique et les phénomènes électromagnétique et thermique afin modéliser l'écoulement du bain de verre fondu. Le modèle final permet de fournir de diverses grandeurs, notamment des estimations pour le temps de vidange, le flux thermique et l'évolution temporelle du débit massique et de la température dans le fourThis thesis is part of the development of a new technology of oxides melting in a furnace heated by induction. The technology studied involves strong interactions between electromagnetic, thermal and hydrodynamic phenomena in a flow with physical properties strongly dependents of the temperature. The aim of the thesis is the modelling of the process by coupling closely the Joule heating, the mechanical stirring and the draining of the furnace. The modeling of the time evolution of the interface between glass and air during the emptying of the cold crucible was performed. Regarding the methodology, we chose to combine two scientific codes: Flux® for the electromagnetic calculation and Fluent® for thermal-hydraulics. The evolution of the free surface was treated by the multiphasic method "Volume -Of- Fluid - VOF" and the mechanical stirring by the “Moving Reference Frame” and the “Sliding Mesh”. First of all, we considered the draining of a tank filled with a silicon oil of high-viscosity without mechanical stirring. This initial model took into account studies of hydraulic similarity between the silicon oil and the glass. Then we superimposed the forced flow creates by the mechanical stirrer, the thermal and the electromagnetic phenomena in order to model the flow of the molten glass. The final model can provide various parameters, including the time needed to drain the furnace, the heat transfer flux and the time evolution of the mass flow rate and of the temperature inside de furnace
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Magnusson, Mats O. "Pharmacodynamics of Enzyme Induction and its Consequences for Substrate Elimination." Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis Acta Universitatis Upsaliensis, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-7812.
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Ndzogha, Cyrille. "Etudes des phénomènes d’échange dans la purification du silicium par plasma et induction." Grenoble INPG, 2005. https://theses.hal.science/tel-01340596.
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Ce travail de thèse porte sur un procédé plasma de purification de silicium pour usages photovoltaïque. Il est appliqué à deux types de matériaux : du silicium d’origine métallurgique et des produits de recyclage des boues de sciage des lingots et des plaquettes de la filière photovoltaïque. Les boues de sciage des plaquettes sont essentiellement constituées de liquide de coupe, de particules de SiC (abrasif), de microparticules de silicium et de microparticules de fer provenant du fil de découpe. Le silicium de ces boues est un silicium de haute pureté, qui est déjà de qualité photovoltaïque. Il peut représenter jusqu’`a 60 % du poids initial du lingot. Le procédé objet du projet comporte une phase de séparation du SiC par centrifugation, suivi d’une phase d’élimination chimique du fer, puis d’un traitement par plasma réactif pour l’élimination du SiC résiduel. Ce travail porte sur cette dernière phase. Un traitement plus complexe que celui initialement prévu a été rendu nécessaire par l’existence dans les boues de sciage de particules de SiC provenant du bris des grains de l’abrasif initial. La séparation du SiC étant incomplète, le traitement par plasma a dû éliminer des quantités beaucoup plus importantes qu’initialement prévu. Cela a nécessité une modification importante du procédé initial, et la mise au point de phase de pré-traitement destiné à rendre exploitable par le plasma le produit issu de la séparation. Ce travail combine études théoriques, modélisations numériques et expérimentation. La modélisation thermodynamique permet de déterminer les meilleures conditions d’élimination des polluants (gaz réactifs adaptés, débits, températures, pressions) tandis que la modélisation du brassage électromagnétique mesure l’efficacité du renouvellement de la surface du bain liquide au cours du traitementThis thesis focuses on a plasma process of purification of silicon for photovoltaic applications. It is applied to two types of materials: metallurgical silicon and recycling products from sawing sludge ingots and from wafers of photovoltaic industry. Platelet sawing sludge consist mainly of cutting fluid, SiC particles (abrasive), silicon microparticles and iron micro-particles from the cutting wire. Silicon sludge is a high-purity silicon, which is already of photovoltaic quality. It can represent 60% of the original weight of the ingot. The present process comprises a SiC phase separation by centrifugation, followed by chemical elimination phase of the iron, then a reactive plasma treatment for removing residual SiC. This work deals with this last phase. A more complex treatment than originally planned was made necessary by the existence in the SiC particles of sawing sludge from the initial breaking of the abrasive grains. Separation of SiC is incomplete, the plasma treatment had to remove much larger quantities than originally planned. This required a significant modification of the original process, and the setting of a pre-treatment phase point intended to make it usable by the product of the plasma separation. This work combines theoretical studies, numerical modeling and experimentation. Thermodynamic modeling to determine the best conditions for the removal of pollutants (adapted reactive gases, flow rates, temperatures, pressures) whereas modeling the electromagnetic measurement brewing efficiency renewing the surface of the liquid bath during treatment
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Carlsson, Björn. "Modellbygge och regulatordesign av tröghetsmomentsimulator tillreferenssystem för stridsvagn 122." Thesis, Linköping University, Department of Electrical Engineering, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-2162.
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This master thesis holds a modelling in Simulink for a physical model of a main battletank tower, a three-phase induction motor and some mechanics. The aim of this work is to connect an earlier project at AerotechTelub, named StabSim to another called Eldris. In StabSim it has been made a Simulink model of the align and stabilisation system in a main battle tank 122 and in Eldris it has been build a physical model of a main battle tank tower.
In this thesis the models that differs between Eldris and a real tower is changed in StabSim, and the parts that only exist in Eldris is added, for example a torque generating system which purpose is to make the model to behave like a real tower in control application, although it only has half the inertia as a real tower.
The thesis even includes proposing a calculation of the torque that the torque generating system will actuate at the model.
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McKay, Allan John. "Geoelectric fields and geomagnetically induced currents in the United Kingdom." Thesis, University of Edinburgh, 2004. http://hdl.handle.net/1842/639.
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This thesis investigates geo-electric fields in the United Kingdom with particular regard to Geomagnetically Induced Currents (GIC) in the Scottish Power electricity transmission network (SPTN). The joint spectral characteristics of Scottish Power GIC and Eskdalemuir magnetic observatory data are analysed, and GIC are shown to be coherent with magnetic field variations over the period range 2-1100s. A bi-variate transfer function model of the physical link between magnetic field variations and GIC demonstrates that long-period (>200s) induction makes a first order contribution to the observed GIC at one SPTN site, and dominates the response at another. Thin-sheet modelling at a period of 750s is used to explore the relative influence of three factors on the size and spatial distribution of the calculated electric field: (i) the contrast in conductance between the sea and the land; (ii) variations in conductance due to sea depth; (iii) lateral variations in conductance representative of those in the geographic area occupied by the SPTN. The modelling suggests that a `coast-only' model (i) will over-predict electric field magnitudes in the SPTN region by a factor of 2-5 in comparison with model (iii). Distortion analysis of Magnetotelluric (MT) data at a period of 750s acquired over numerous field campaigns reveal pervasive galvanic distortion of the electric field in the SPTN region. GIC transfer functions of one site are consistently interpreted as proxy MT responses, and it is shown that galvanic distortion of the electric field modifies significantly the GIC amplitude response. A prototype model of the SPTN developed by the British Geological Survey and the Finnish Meteorological Institute is used to calculate GIC. It is shown that neglect of lateral variations of conductivity may lead to false conclusions about the direction of the external electric field that maximises GIC. Time derivatives of the Eskdalemuir horizontal magnetic field are used as an index of GIC activity, and to select events which may have led to large GIC in the time period (1983-2000) prior to the monitoring of GIC by Scottish Power. Backwards-prediction using the GIC transfer functions and observatory magnetic data suggests that GIC at the Scottish Power monitoring sites have amplitudes less than approximately 30A.
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Boulanger, Isabelle. "Lillgrund Wind Farm Modelling and Reactive Power Control." Thesis, KTH, Elektriska energisystem, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-119256.
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The installation of wind power plant has significantly increased since several years due to the recent necessity of creating renewable and clean energy sources. Before the accomplishment of a wind power project many pre-studies are required in order to verify the possibility of integrating a wind power plant in the electrical network. The creation of models in different software and their simulation can bring the insurance of a secure operation that meets the numerous requirements imposed by the electrical system. Hence, this Master thesis work consists in the creation of a wind turbine model. This model represents the turbines installed at Lillgrund wind farm, the biggest wind power plant in Sweden. The objectives of this project are to first develop an accurate model of the wind turbines installed at Lillgrund wind farm and further to use it in different kinds of simulations. Those simulations test the wind turbine operating according to different control modes. Also, a power quality analysis is carried out studying in particular two power quality phenomena, namely, the response to voltage sags and the harmonic distortion. The model is created in the software PSCAD that enables the dynamic and static simulations of electromagnetic and electromechanical systems. The model of the wind turbine contains the electrical machine, the power electronics (converters), and the controls of the wind turbine. Especially, three different control modes, e.g., voltage control, reactive power control and power factor control, are implemented, tested and compared. The model is tested according to different cases of voltage sag and the study verifies the fault-ride through capability of the turbine. Moreover, a harmonics analysis is done. Eventually the work concludes about two power quality parameters.
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Petzold, Thomas [Verfasser], Dietmar [Akademischer Betreuer] Hömberg, and Alfred [Akademischer Betreuer] Schmidt. "Modelling, analysis and simulation of multifrequency induction hardening / Thomas Petzold. Gutachter: Dietmar Hömberg ; Alfred Schmidt. Betreuer: Dietmar Hömberg." Berlin : Technische Universität Berlin, 2014. http://d-nb.info/1066162824/34.
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Sprooten, Jonathan. "Finite element and electrical circuit modelling of faulty induction machines: Study of internal effects and fault detection techniques." Doctoral thesis, Universite Libre de Bruxelles, 2007. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/210674.
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This work is dedicated to faulty induction motors. These motors are often used in industrial applications thanks to their usability and their robustness. However, nowadays optimisation of production becomes so critical that the conceptual reliability of the motor is not sufficient anymore. Motor condition monitoring is expanding to serve maintenance planning and uptime maximisation. Moreover, the use of drive control sensors (namely stator current and voltage) can avoid the installation and maintenance of dedicated sensors for condition monitoring.Many authors are working in this field but few approach the diagnosis from a detailed and clear physical understanding of the localised phenomena linked to the faults. Broken bars are known to modulate stator currents but it is shown in this work that it also changes machine saturation level in the neighbourhood of the bar. Furthermore, depending on the voltage level, this change in local saturation affects the amplitude and the phase of the modulation. This is of major importance as most diagnosis techniques use this feature to detect and quantify broken bars. For stator short-circuits, a high current is flowing in the short-circuited coil due to mutual coupling with the other windings and current spikes are flowing in the rotor bars as they pass in front of the short-circuited conductors. In the case of rotor eccentricities, the number of pole-pairs and the connection of these pole-pairs greatly affect the airgap flux density distribution as well as the repartition of the line currents in the different pole-pairs.
These conclusions are obtained through the use of time-stepping finite element models of the faulty motors. Moreover, circuit models of faulty machines are built based on the conclusions of previously explained fault analysis and on classical Park models. A common mathematical description is used which allows objective comparison of the models for representation of the machine behaviour and computing time.
The identifiability of the parameters of the models as well as methods for their identification are studied. Focus is set on the representation of the machine behaviour using these parameters more than the precise identification of the parameters. It is shown that some classical parameters can not be uniquely identified using only stator measurements.
Fault detection and identification using computationally cheap models are compared to advanced detection through motor stator current spectral analysis. This last approach allows faster detection and identification of the fault but leads to incorrect conclusions in low load conditions, in transient situations or in perturbed environments (i.e. fluctuating load torque and unideal supply). Efficient quantification of the fault can be obtained using detection techniques based on the comparison of the process to a model.
Finally, the work provides guidelines for motor supervision strategies depending on the context of motor utilisation.
Doctorat en Sciences de l'ingénieur
info:eu-repo/semantics/nonPublished
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Hikkaduwa, Liyanage Diana Aroshanie. "Modelling and control of a novel single phase generator based on a three phase cage rotor induction machine." Thesis, Curtin University, 2015. http://hdl.handle.net/20.500.11937/250.
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This thesis develops the mathematical modelling and the closed loop control of a single-phase induction generator based on a three-phase cage rotor machine suitable for renewable energy conversion. Comprehensive dynamic and steady state models are developed in stationary ‘αβ’ reference frame and the accuracy is verified by comparing the theoretical results with the laboratory experimental results. Closed loop feedback regulator is designed to regulate the output voltage and frequency at the rated conditions.
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Astfalck, Allen Electrical Engineering Australian Defence Force Academy UNSW. "Analysis of electromagnetic force and noise in inverter driven induction motors." Awarded by:University of New South Wales - Australian Defence Force Academy. School of Electrical Engineering, 2002. http://handle.unsw.edu.au/1959.4/38671.
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This thesis is part of a major research project to analyse vibro-acoustic characteristics from variable speed inverter driven induction motors (VSIDIM). The overall projects??? aimed at providing a better understanding of the mechanisms of sound generation from electromagnetic origins and developing a numerical model to predict the sound power emitted from a VSIDIM. The scope of this thesis is to assess experimentally the effect of various controller strategies on the radiated sound power and to develop a finite element method for calculating the electromagnetic force distribution over the stator. Various sources of noise in induction motors and their behaviour with speed and load have been reviewed. Models of the electromagnetic field and vibro-acoustic character have been discussed. An outline of various techniques of reducing noise in induction motors through design of inverters and modifications to the motor structure has been given. Experiments were conducted to assess the effect of controller strategies on the radiated sound power. Three different supplies were tested: a dynamotor which produces an almost sinusoidal supply with very low harmonic content, an inverter with a low switching frequency (less than 1kHz) and an inverter with a high switching frequency (8kHz) and various levels of random modulation. Results indicate that the sound power level of the MSC drive is a lot higher than that of the VSC 2000 drive and the dynamotor drive. The sound power level of the VSC 2000 drive and the dynamotor drive increases almost linearly with motor speed, that for the MSC drive is almost independent of speed. The sound power level of the MSC drive is almost 28dB higher than that of the dynamotor drive at 450rpm and the difference is reduced to 14dB at 1500rpm where the aerodynamic noise becomes more dominant. It has been found that at the rated speed (1500rpm), the sound power level varies by less than 3dB from no load to full load for all three sources. Although increasing the switching frequency increases the cost of the inverters and switching losses, results from the MSC and VSC 2000 drives clearly show that it reduces the radiated sound power by shifting the harmonics into higher and inaudible frequency range. The tonal nature around the switching frequency has been reduced by increasing the levels of random modulation to spread the energy over a wider range of frequencies, although the sound power level has not varied by more than 0.2dB. A finite element model has been developed to calculate the electromagnetic force distribution. The quasi-static solution method has been implemented by stepping the rotor through the time domain using a fine regular mesh in the air gap. The stator currents were experimentally obtained while the rotor currents were obtained using a 4 parameter state space model of the motor. Results of the simulation indicate the influence of stator and rotor slots, saturation and time harmonics in the current. The calculated electromagnetic force distribution has been used in a FEM/BEM acoustic model and SEA acoustic model to predict the radiated sound power which agrees reasonably well with the measured sound, thus validating indirectly the electromagnetic force simulations.
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Paya, Bernard. "Optimisation des installations de chauffage de billettes par induction électromagnétique dans l’industrie de la forge afin d’améliorer son efficacité énergétique." Thesis, Université Grenoble Alpes (ComUE), 2017. http://www.theses.fr/2017GREAI115/document.
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La première partie de ce mémoire donne un panorama des trente années de recherche passées au sein de la R&D d’EDF dans le domaine du chauffage par induction dans l’industrie. Les différentes actions menées ont porté sur différentes thématiques : les travaux de modélisation numérique, l’expertise en chauffage par induction dans ses secteurs traditionnels, le développement de solutions innovantes dans d’autres secteurs industriels, La conduite de projet internes R&D puis projets externes avec des financements publics français ou européens, le rayonnement international et le soutien aux jeunes.La deuxième partie présente une synthèse des travaux scientifiques les plus marquants qui ont abouti à la réalisation d’un logiciel d’optimisation des installations de chauffage par induction de billettes afin d’en améliorer les performances énergétiques. La modélisation numérique du chauffage est abordée en 1D par le couplage entre un calcul électromagnétique par la méthode des éléments finis et pas à pas dans le temps et un calcul thermique transitoire par la méthode des différences finies implicites. Le domaine de validité du modèle 1D a été étendu par la mise en place de coefficients correctifs sur le champ magnétique. Les travaux concernant l’inducteur permettent de décrire précisément leur comportement électrique (résistance) et thermique (refroidissement) ; une solution de récupération est même proposée. La modélisation simplifiée de l’onduleur à résonance alimentant l’inducteur permet de décrire son comportement global sans devoir entrer dans les détails de fonctionnement de l’électronique de puissance : suivi de la fréquence de résonance du circuit oscillant, adaptation des consignes à l’impédance du circuit et aux limitations du générateur. Les données électromagnétiques des matériaux et leur évolution avec la température sont mesurées à l’aide d’un équipement conçu sur-mesure. Ces différents travaux sont validés par comparaison avec des modèles numériques plus complexes et avec des expérimentations. Des processus d’optimisation énergétique de la chauffeuse ont été élaborés agissant, soit sur les paramètres électriques de la ligne, soit sur la conception d’un nouvel inducteur.Mémoire de doctorat présenté dans le cadre de la « Validation des Acquis par l’Expérience »The first part of this dissertation gives an overview of thirty years of research work done in the frame of EDF R&D Division in the domain of industrial induction heating. The different works concerned many themes: numerical modelling, expertise in induction heating in conventional sectors, development of innovative solutions in other industrial sectors, project management inside EDF first, then collaborative projects with French or European financial support, international recognition and support for young researchers.The second part shows a summary of the most relevant scientific works which leaded to a software of billet induction heating optimisation in order to improve its energy efficiency. Numerical modelling is approached in a 1D configuration, coupling an electromagnetic model using a finite elements and step by step in time method with a thermal transient model using an implicit finite difference method. The validity domain is extended thanks to the use of an attenuation coefficient applied to the magnetic field. Works regarding inductor allows to describe more accurately the electrical (resistance) and thermal (cooling) behaviour; a solution for energy recovery is also proposed. The simplified model of the resonant inverter supplying the inductor allows to describe globally its behaviour without going deep in the details of the power electronics: following the resonant frequency of the oscillating circuit, adapting the set points to the circuit impedance and the power supply limitations. Electromagnetic physical data of metals and their evolution with temperature are measured with a tailor-made equipment. All these works are validated by comparison with more complex numerical models or with experiments. Energy optimisation procedures for the heating device are developed, acting either on the line electrical parameters or on the design of a new inductor.PhD dissertation presented in the frame of the “Validation of Professional Experience”
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Zhang, Yali. "The Role of Negative Emotions in Constructing Meaning in Interactive Contexts." Thesis, Queensland University of Technology, 2019. https://eprints.qut.edu.au/132451/1/Yali_Zhang_Thesis.pdf.
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This research explores the potential of negative emotions in creating meaningful user experience. It investigates the transformation of negative emotions during interactions and its functional consequences on meaning perception. The causes of specific negative emotions in different contexts of interactions and their effects on cognition and behaviours were examined. The findings reveal the mechanism of changes in emotions over the course of interactions. The predominant role of negative emotions in the meaning-making process is demonstrated. This research outcome consists of two conceptual models for modelling meaningful experiences and systematic methods of emotion induction in users.