Thesis (Ph. D.)--University of Wisconsin--Madison, 1974. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

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High voltage power transformers are designed to withstand a variety of overvoltages and short circuit forces. Occurrence of these events in a power system is natural, inevitable, and one of the main causes of transformer failure. Therefore, an early and reliable detection of an incipient fault is paramount. To this end, diagnostic testing and condition monitoring, not only enables power utilities in early detection of incipient fault-like conditions, but also is a practical way of optimizing existing assets, lowering operating costs, scheduling maintenance, preventing unplanned outages, etc. and consequently improve efficiency. Over the years, many monitoring and diagnostic methods have evolved. In par- ticular, low voltage impulse and frequency response analysis or transfer function approaches have emerged as useful tools in detecting winding deformations. Literature study reveals that although much has been acclaimed about these methods, advancement in interpretation of acquired data must be rigorously pursued, to facilitate a more meaningful assessment. As a matter of fact, diagnosis (which means interpretation of monitored data) has at-the-most been confined to a mere comparison of two subsequently acquired data sets. This philosophy certainly needs to be improved, to realize the true potential of monitoring/diagnostic tools. Achieving this goal calls for newer impetus. It is natural that there will arise many problems while achieving this goal and they will have to be resolved. Keeping these aspects in mind, the objective of this thesis was aimed at developing Solutions to two specific topics that are closely related to and concern the transformer winding, namely, * An efficient solution to the generalized model of a transformer winding, with no particular limitation on the size of network and number of windings, no restriction on circuit topology and terminal condition, etc. * Propose a method to locate the position, quantum and type of change (i.e. deformation) a model winding undergoes, based on terminal measurements. Details of these approaches are presented in this thesis, which is divided into two parts. 1. A comprehensive analysis of the behaviour of a transformer winding under impulse excitation and its interaction with adjacent windings was until now severely limited, due to the simplifying assumptions imposed (by the existing approaches), like neglecting interaction with neighbouring windings, Ignoring loss, considering only a few sections, etc. thereby rendering the computed results less accurate. A solution considering all these aspects often times results in a very large-sized circuit that needs to be solved. Although circuit simulation software afford iterative solutions, a direct estimation of poles and zeros of any desired network function is not possible. In the first part of the thesis, a novel and closed-form (i.e. analytical) solution based on state space analysis is proposed. It is shown, how the renders the entire computation to be purely numeric. Thus, time-consuming symbolic manipulations are avoided. With this feature, there is practically no limit on the size of network and no restriction on circuit topologies that can be considered. So, virtually any number of windings of a transformer can be considered, permitting a comprehensive analysis of winding behaviour and its interactions. Further, the formulation also permits computation of poles and zeros of any desired network function (e.g. transfer admittance), response to any excitation (e.g. neutral current, transferred surge), estimation of voltage distribution, etc. with little extra effort. Hence, it would be apppropriate to term the proposed method as a \Generalized" solution. For the sole purpose of demonstration, a large-sized network (representing a two-winding transformer with 250 sections/winding) was solved and required only 700 seconds. This shows the time-efficiency achieved, and also that it is free from issues like numerical instability, convergence problems, etc. encountered in some of the existing methods. 2. Detection of mechanical deformation in transformer windings can be achieved with a fair degree of sensitivity using frequency response methods. However, a major challenge that has remained elusive is ascertaining the \extent of damage" and likewise \its location along the winding". It is needless to say that finding these answers is crucial. Ideally, a diagnosis tool is expected to be endowed with powers to answer these questions. Therefore, it is desirable to explore alternative ways of harnessing these embedded features, if any. This was the next motivation. Obviously, a direct solution to this problem on an actual transformer winding is far too complex. Hence, in this preliminary effort a solution was attempted considering a model winding. However, care was taken to incorporate other winding-related nuances as far as practicable. The method was formulated based on quantities measured at the terminals. In the second part of the thesis, a novel algorithm is proposed for determining the location, extent and type of changes intrroduced in a model winding, based on terminal measurements. It employs the well-known properties of driving-point functions and adopts an iterative circuit synthesis approach. From knowledge of the measured short-circuit and open-circuit natural frequencies, and some relevant winding design data, an equivalent circuit was synthesized (called reference circuit). Next, changes were introduced at different locations in the model winding and natural frequencies measured again. Corresponding to every new set of measured natural frequencies, a fresh circuit was synthesized (with topology remaining unchanged). A comparison of these circuits with the reference circuit revealed that a mapping could be established between changes introduced in the model winding and those predicted by the synthesized circuits. Initially, the underlying principle is discussed, and thereafter, the experimental results are presented for both continuous-disc and interleaved winding representations. The case studies involved examples wherein changes in the model winding were made to elements connected to a single tap, two physically different tap positions, multiple changes to different elements, and so on. In all cases, the positions of all the `changes' were reasonably well locatable, and so was the `type of change'. The results were very encouraging. In summary, localization of changes based on terminal measurements, is shown to be a possibility. Lastly, it is conjectured that these findings could be of some assistance in addressing the ultimate task of locating mechanical deformations in actual transformer windings.

No description available.

Electrical machines are subject to different types of failures. Early detection of the incipient faults and fast maintenance may prevent costly consequences. Fault diagnosis of wind turbine is especially important because they are situated at extremely high towers and therefore inaccessible. For offshore plants, bad weather can prevent any repair actions for several weeks. In some of the new wind turbines synchronous generators are used and directly connected to the grid without the need of power converters. Despite intensive research efforts directed at rotor fault diagnosis in induction machines, the research work pertinent to damper winding failure of synchronous machines is very limited. This dissertation is concerned with the in-depth study of damper winding failure and its traceable symptoms in different machine signals and parameters. First, a model of a synchronous machine with damper winding based on the winding function approach is presented. Next, simulation and experimental results are presented and discussed. A specially designed inside-out synchronous machine with a damper winding is employed for the experimental setup. Finally, a novel analytical method is developed to predict the behavior of the left sideband amplitude for different numbers and locations of the broken bars. This analysis is based on the magnetic field theory and the unbalanced multiphase circuits. It is found that due to the asymmetrical structure of damper winding, the left sideband component in the stator current spectrum of the synchronous machine during steady state asynchronous operation is not similar to that of the induction machine with broken bars. As a result, the motor current signature analysis (MCSA) for detection rotor failures in the induction machine is usable to detect broken damper bars in synchronous machines. However, a novel intelligent-systems based approach is developed that can identify the severity of the damper winding failure. This approach potentially can be used in a non-invasive condition monitoring system to monitor the deterioration of a synchronous motor damper winding as the number of broken bars increase over time. Some other informative features such as speed spectrum, transient time, torque-speed curve and rotor slip are also found for damper winding diagnosis.

The fully-pitched winding arrangement is one of the most radical changes in the design of doubly-salient reluctance motors in recent times. By replacing conventional shortpitched windings with fully-pitched windings, the resulting machine has a strong and position dependant mutual coupling between phases. The major torque producing mechanism is due to changes in mutual inductance with rotor position. This enables the windings to be better utilised, and with correct selection of excitation all phases can contribute useful torque all of the time. The increased winding utilisation requires a lower MMF per phase in comparison with a short-pitch wound machine with a single phase excited. Given a suitable winding configuration and machine dimensions, the copper losses for a given torque can be significantly lower than an equivalent conventional switched reluctance machine. Operation of a three phase fully-pitched winding switched reluctance machine has been studied theoretically, in simulation and experimentally. The experimental drive comprises of a D132 frame 12:8 machine, IGBT power converter and DSP controller. Operation with unipolar phase currents has been investigated over a wide speed range and performance compared with a conventional switched reluctance machine. Bipolar operation with several different excitation patterns has been investigated. Unipolar operation gives the largest torque/speed envelope with a simple controller, although bipolar modes can equal this with a more complex controller. Results show that for equal RMS phase current the average torque produced by four different modes of excitation are approximately equal. However, there is a large difference in the torque ripple and acoustic noise performance of each mode. Current control in switched reluctance machines is complicated by the non-linear nature of the load. By controlling flux-linkage rather than current a linear load model can be used. A discrete time 'dead-beat' flux-linkage controller has been implemented which gives superior phase current control performance to other types of controller with the same sample interval. A new method of constant torque operation based on 'flux ramps' has been proposed. This method gives predictable performance and enables constant torque operation over a wide speed range. A Genetic Algorithm has been shown to be very effective when applied to the problem of optimising the 'flux ramps' for minimum torque ripple. A speed controller has been implemented which makes use of the Genetic Algorithm optimised flux ramps to give smooth torque over a wide speed range.

El texto completo de este trabajo no está disponible en el Repositorio Académico UPC por restricciones de la casa editorial donde ha sido publicado. / This work describes the design of an external cleaning system for fire hoses with an external polyester or rubber jacket. This device is intended as a tool for simple and effective external cleaning. Within the capabilities of the equipment is the washing and winding of a hose. This is made up of a washing chamber, which contains a group of sprinklers inside with a brushing system and a winding mechanism with a platform designed to carry out the type of winding snail or single donut. Cleaning can be applied to both types of coatings with the action of a selector switch, the variables involved are adjusted accordingly. The system aims to perform its functions without damaging the composition of the hose lining material, in addition to reducing the space required during cleaning.

Thermoplastic composite filament winding is an on-line consolidation process, where the composite experiences a complex temperature history and undergoes a number of temperature history affected microstructural changes that influence the structure's subsequent properties. These changes include melting, crystallization, void formation, degradation and consolidation. In the present study, models of the thermoplastic filament winding process were developed to identify and understand the relationships between process variables and the structure quality. These include models that describe the heat transfer, consolidation and crystallization processes that occur during fabrication of a filament wound composites structure. A comprehensive thermal model of the thermoplastic filament winding process was developed to calculate the temperature profiles in the composite substrate and the towpreg temperature before entering the nippoint. A two-dimensional finite element heat transfer analysis for the composite-mandrel assembly was formulated in the polar coordinate system, which facilitates the description of the geometry and the boundary conditions. A four-node 'sector element' was used to describe the domain of interest. Sector elements were selected to give a better representation of the curved boundary shape which should improve accuracy with fewer elements compared to a finite element solution in the Cartesian-coordinate system. Hence the computational cost will be reduced. The second thermal analysis was a two-dimensional, Cartesian coordinate, finite element model of the towpreg as it enters the nippoint. The results show that the calculated temperature distribution in the composite substrate compared well with temperature data measured during winding and consolidation. The analysis also agrees with the experimental observation that the melt region is formed on the surface of the incoming towpreg in the nippoint and not on the substrate. Incorporated with the heat transfer analysis were the consolidation and crystallization models. These models were used to calculate the degree of interply bonding and the crystallinity achieved during composite manufacture. Bonding and crystallinity developments during the winding process were investigated using the model. It is concluded that lower winding speed, higher hot-air heater nozzle temperature, and higher substrate preheating temperature yield higher nippoint temperature, better consolidation and a higher degree of crystallization. Complete consolidation and higher matrix crystallization will result in higher interlaminar strength of the wound composite structure. / Master of Science

Na busca pela substituição dos materiais convencionais por materiais com alto desempenho estrutural nos mais variados setores do mercado, os materiais compósitos têm recebido cada vez mais a confiança dos engenheiros projetistas. Isto devido às características, comparadas com materiais convencionais como: baixa densidade associada à excelente rigidez e resistência estrutural, alta resistência à corrosão, resistência à temperaturas elevadas e ótimos resultados estéticos. Um dos processos de fabricação bastante utilizado para a produção de peças nestes materiais é o processo conhecido como Filament Winding ou \"Enrolamento Filamentar\". Essa técnica consiste em revestir a superfície de um mandril, através do enrolamento de fibras contínuas impregnadas por um banho de resina. As fibras utilizadas nesse processo, geralmente de vidro ou de carbono são posicionadas em uma trajetória calculada por algoritmos matemáticos que determinam o seu posicionamento adequado, o que está diretamente relacionado às propriedades mecânicas desejadas na peça final. Desta forma, este trabalho tem por objetivo desenvolver um sistema computacional para o cálculo da trajetória de deposição da fibra sobre o mandril e seu seqüenciamento durante o processo de Filament Winding. Foram desenvolvidas e implementadas computacionalmente estratégias para os revestimentos circular, helicoidal e polar utilizando trajetórias geodésicas, o que abrange a grande maioria das peças fabricadas por este processo. Os resultados foram validados com exemplo da literatura e, também através de interface com sistema CAD. / ln the search for the replacement of conventional materials by those with high structural performance, the reinforced composite materials have increasingly used by engineers during the product development process. The main reasons lies in their excellent characteristics compared to conventional materials such as: low-density associated with high stiffness and strength, good tolerance to corrosion, resistance to high temperatures and good aesthetic results. One of the manufacturing processes most used to produce composite parts is the Filament Winding. This technique consists in winding continuous impregnated fiber by a bath of resin along a mandrel. The fibers used are generally of glass or carbon, guided through a trajectory calculated by mathematical algorithms. Because of the importance of this study, this work proposes and develops a computational system to calculate the trajectories and sequences of the fiber in the Filament Winding process, considering geodesic trajectories during the hoop, helical and polar winding, which cover the majority of parts produced by this process. The routines and system are validated with the literature as well as in the CAD system.

Na busca pela substituição dos materiais convencionais por materiais com alto desempenho estrutural nos mais variados setores do mercado, os materiais compósitos têm recebido cada vez mais a confiança dos engenheiros projetistas. Isto devido às características, comparadas com materiais convencionais como: baixa densidade associada à excelente rigidez e resistência estrutural, alta resistência à corrosão, resistência à temperaturas elevadas e ótimos resultados estéticos. Um dos processos de fabricação bastante utilizado para a produção de peças nestes materiais é o processo conhecido como Filament Winding ou \"Enrolamento Filamentar\". Essa técnica consiste em revestir a superfície de um mandril, através do enrolamento de fibras contínuas impregnadas por um banho de resina. As fibras utilizadas nesse processo, geralmente de vidro ou de carbono são posicionadas em uma trajetória calculada por algoritmos matemáticos que determinam o seu posicionamento adequado, o que está diretamente relacionado às propriedades mecânicas desejadas na peça final. Desta forma, este trabalho tem por objetivo desenvolver um sistema computacional para o cálculo da trajetória de deposição da fibra sobre o mandril e seu seqüenciamento durante o processo de Filament Winding. Foram desenvolvidas e implementadas computacionalmente estratégias para os revestimentos circular, helicoidal e polar utilizando trajetórias geodésicas, o que abrange a grande maioria das peças fabricadas por este processo. Os resultados foram validados com exemplo da literatura e, também através de interface com sistema CAD. / ln the search for the replacement of conventional materials by those with high structural performance, the reinforced composite materials have increasingly used by engineers during the product development process. The main reasons lies in their excellent characteristics compared to conventional materials such as: low-density associated with high stiffness and strength, good tolerance to corrosion, resistance to high temperatures and good aesthetic results. One of the manufacturing processes most used to produce composite parts is the Filament Winding. This technique consists in winding continuous impregnated fiber by a bath of resin along a mandrel. The fibers used are generally of glass or carbon, guided through a trajectory calculated by mathematical algorithms. Because of the importance of this study, this work proposes and develops a computational system to calculate the trajectories and sequences of the fiber in the Filament Winding process, considering geodesic trajectories during the hoop, helical and polar winding, which cover the majority of parts produced by this process. The routines and system are validated with the literature as well as in the CAD system.