The McTronX research group at the North–West University designs and develops Active Magnetic Bearings (AMBs). The group’s focus shifted to the design and development of AMB supported drive systems. This includes the electromagnetic and mechanical design of the electric machine, AMBs, auxiliary bearings as well as the development of the control system. The research group is currently developing an AMB supported high speed Induction Machine (IM) drive system that will facilitate tests in order to verify the design capability of the group. The research presented in this thesis describes the mechanical design and manufacturing of a high speed IM rotor section. The design includes; selecting the IM rotor topology, material selection, detail stress analysis and selecting appropriate manufacturing and assembly procedures. A comprehensive literature study identifies six main design considerations during the mechanical design of a high speed IM rotor section. These considerations include; magnetic core selection, rotor cage design, shaft design, shaft/magnetic core connection, stress due to operation at elevated temperatures and design for manufacture and assemble (DFMA). A critical overview of the literature leads to some design decisions being made and is used as a starting point for the detail design. The design choices include using a laminated cage rotor with a shrink fit for the shaft/magnetic core connection. Throughout the detail design an iterative process was followed incorporating both electromagnetic and mechanical considerations to deliver a good design solution. The first step of the iterative design process was, roughly calculating the material strengths required for first iteration material selection followed by more detailed interference fit calculations. From the detail stress analysis it became apparent that the stress in the IM rotor section cannot be calculated accurately using analytical methods. Consequently, a systematically verified and validated Finite Element Analysis (FEA) model was used to calculate the interferences required for each component. The detail stress analysis of the assembly also determined the allowable manufacturing dimensional tolerances. From the detail stress analysis it was found that the available lamination and squirrel cage material strengths were inadequate for the design speed specification of 27,000 r/min. The analysis showed that a maximum operating speed of 19,000 r/min can be achieved while complying with the minimum factor of safety (FOS) of 2. Each component was manufactured to the prescribed dimensional tolerances and the IM rotor section was assembled. With the failure of the first assembly process, machine experts were consulted and a revised process was implemented. The revised process entailed manufacturing five small lamination stacks and assembling the stack and squirrel cage afterwards. The end ring/conductive bar connection utilises interference fits due to the fact that the materials could not be welded. The process was successful and the IM rotor section was shrink fitted onto the shaft. However, after final machining of the rotor’s outer diameter (OD), inspections revealed axial displacement of the end rings and a revised FEA was implemented to simulate the effect. The results indicated a minimum FOS 0.6 at very small sections and with further analytical investigation it was shown that the minimum FOS was reduced to only 1.34. Although the calculations indicated the FOS was below the minimum prescribed FOS ? 2, the rotor spin tests were scheduled to continue as planned. The main reasons being that the lowest FOS is at very small areas and is located at non critical structural positions. The fact that the rotor speed was incrementally increased and multiple parameters were monitored, which could detect early signs of failure, further supported the decision. In testing the rotor was successfully spun up to 19,000 r/min and 27 rotor delevitation test were conducted at speeds of up to 10,000 r/min. After continuous testing a secondary rotor inspection was conducted and no visible changes could be detected. The lessons learnt leads to mechanical design and manufacturing recommendations and the research required to realise a 27,000 r/min rotor design. / Thesis (M.Ing. (Mechanical Engineering))--North-West University, Potchefstroom Campus, 2011.

Orientador: Dr. Alfeu J. Sguarezi Filho / Dissertação (mestrado) - Universidade Federal do ABC, Programa de Pós-Graduação em Engenharia Elétrica, 2016. / A energia eólica é uma fonte de energia renovável com diversas vantagens e sua participação na matriz energética mundial está crescendo a cada ano. Nos últimos anos, as plantas eólicas têm passado por grandes mudanças devido às novas tecnologias desenvolvidas para as Smart Grids (SG). Cada vez mais, os sistemas de conversão de energia eólicos estão utilizando arquiteturas de comunicação mais desenvolvidas para possibilitar o compartilhamento de dados e medidas em fazendas eólicas inteligentes. Nesse contexto, a proposta desse estudo é um controle sem fio para um gerador de indução gaiola de esquilo (GIGE) de velocidade variável conectado coma rede elétrica. O sistema de comunicação sem fio é empregado para enviar as potências de referência para o controlador do GIGE com a confiabilidade necessária para garantir a qualidade da energia fornecida pelo aerogerador. Neste trabalho, no controle do gerador é utilizada a técnica de controle do Controle Direto de Torque (CDT) e controle orientado pela tensão (COT) para a conexão com a rede elétrica. Para o sistema de comunicação sem fio, foram utilizadas duas estratégias de baixo custo e ampla cobertura nacional, baseadas nas redes de dados GPRS e EGPRS. O desempenho do sistema é avaliado através de diversas simulações e testes. / Wind energy is a renewable source of energy with several advantages and the participation in the global energy matrix is increasing every year. In recent years, the wind farms were changing with the advance of new technologies developed for the Smart Grid (SG). Increasingly, wind energy conversion systems are using more developed communication architectures to enable data sharing and intelligent measures in wind farms. In this context, the purpose of this study is a wireless controller for a variable speed Squirrel Cage Induction Generator (SCIG) connected to the grid. The wireless system is used to send the reference powers for SCIG controller with the reliability needed to ensure the quality of the power supplied by the wind turbine. In this paper, in the generator's control is used the Control Direct Torque (CDT) technique and Control-Driven Voltage (COT) technique for connection to the power grid. For the wireless communication system, they used two low-cost strategies with national coverage, based on GPRS and EGPRS data networks. The system performance is evaluated through various simulations and tests.

Orientador: Prof°. Dr Alfeu Joãozinho Sguarezi Filho / Dissertação (mestrado) - Universidade Federal do ABC, Programa de Pós-Graduação em Engenharia Elétrica, 2017. / Esta dissertação apresenta o controle preditivo aplicado ao gerador de indução conectado à rede elétrica com emprego de conversor back to back. Nesse caso, o conversor conectado ao gerador é acionado pela técnica de controle preditivo direto de torque. Por sua vez, o conversor da rede é acionado pelo controle preditivo direto de potência. Os controladores são projetados com base em modelo matemático dinâmico discretizado do gerador e da rede. Para validação do sistema proposto, foram implementadas no Sim- PowerSystems do Matlab/Simulink R os modelos matemáticos e os algoritmos de predição. Por m, foram também realizado teste experimentais no laboratório da universidade. Os resultados obtidos serão apresentados a m de demonstrar a melhora na resposta dinâmica do gerador. Para os resultados de simulação foi possível validar a melhora na corrente injetada na rede em comparação às técnicas tradicionais. / This dissertation presents the predictive control applied to the induction generator connected to the electric grid with the back-to-back converter. In this case, the converter connected to the generator is driven by the predictive direct torque control technique and the grid converter is driven by predictive direct power control. The controllers are designed from discrete dynamic generator and grid mathematical model. For the validation of the proposed system, mathematical models and prediction algorithms were implemented in SimPowerSystems of Matlab / Simulink R. Finally, experimental tests were also carried out in the university laboratory. The results obtained will be presented to present the improvement in the dynamic response of the generator, and for the simulation results, it was possible to validate the improvement in the current injected into the grid in relation to the traditional techniques.

Ces travaux de recherche portent sur l’étude de l’injection du cuivre. Dans une optique d’amélioration des propriétés du cuivre injecté sous pression, deux grands thèmes de réflexion ont été abordés. La première voie de réflexion porte sur l’influence des paramètres de fusion et d’éléments d’alliages ajoutés en faible quantité sur les caractéristiques des démonstrateurs technologiques produits. La seconde partie discute de l’influence du procédé de fonderie en lui-même, notamment au travers de l’étude de deux paramètres : l’influence du régime d’écoulement du métal en fusion dans l’empreinte, et l’influence de l’emprisonnement de l’air sur les propriétés des pièces injectées. / This research focuses on the study of high pressure die casting (HPDC) of copper. In order to improve the properties of die-cast copper, two main issues were investigated. In the first part, attention is paid to the influence of melting parameters and of addition of alloying elements in small amounts on the characteristics of the specimen produced. The second part discusses the influence of the foundry process itself on properties of die cast part, in particular by studying two parameters : the metal flow type during cavity filling, and the air entrapment.

No description available.

Der Bewegungsapparat der Sciuromorpha, einer monophyletische Gruppe von ca. 300 Arten, wurde verwendet um den Effekt der Lebensweise und der Körpermasse auf die Scapula- und Femurmorphologie zu untersuchen. Diese Nagetierklade weist eine breite Vielfalt an Lebensweisen (arboreal, fossoriell, aerial) als auch Körpermassen (drei Größenordnungen umfassend) auf. Die fossorielle Lebensweise hat sich höchstwahrscheinlich dreimal unabhängig von einem arborealen Vorfahren entwickelt. Mehr als die Hälfte der rezenten Arten wurden untersucht. Die Scapulae wurden fotografiert, während Computertomographie (CT) und Oberflächenlaserscans für die Femora verwendet wurden. Es wurden funktionsrelevante Merkmale analysiert, wie die effektive Länge der Skelettelemente, die Muskeleigenschaften soweit aus der Geometrie der Knochen ableitbar, sowie die Robustheit. Die CT-Scans wurden verwendet, um die Querschnitts- und Trabekeleigenschaften des Femurs zu analysieren. Die Gestalt wurde mittels geometrischer Morphometrie untersucht. Phylogenetic comparative methods wurden unter anderem verwendet, um den Einfluss der Phylogenie zu beurteilen als auch, ob sich die unabhängige Aneignung einer fossoriellen Lebensweise in der Evolution homoplastischer Morphologien widerspiegelt. Die Phylogenie spielte bei der Merkmalsevolution eine vernachlässigbare Rolle. Das Auftreten signifikanter Merkmalsunterschiede zwischen den Lebensweisen sowie allometrischer Anpassungen aufgrund Veränderungen in der Körpermasse hingen von dem jeweiligen Merkmal ab. Bei einigen Merkmalen unterschied sich der Einfluss der Körpermasse signifikant zwischen den einzelnen Lebensweisen, was aber nicht die Regel zu sein scheint. Die Evolution homoplastischer Morphologien war sehr unwahrscheinlich bei den fossoriellen Gruppen. Diese Ergebnisse deuten auf eine komplexe, aber adaptive Evolutionsgeschichte dieser Skelettelemente bei den Sciuromorpha hin. / The vertebrate locomotor apparatus of Sciuromorpha, a monophyletic group of ca. 300 species, was used to investigate the effect of lifestyle and body mass on the scapular and femoral morphology. This rodent clade displays a broad diversity of lifestyles (arboreal, fossorial, aerial) and body masses spanning three orders of magnitude. The fossorial lifestyle evolved most probably three times independently from an arboreal ancestor. More than half of the extant species were included. Scapulae were photographed and computed tomography (CT) and surface laser scans were acquired for the femora. Functionally relevant traits were analysed, e.g., the effective length of the skeletal element, the properties of attaching muscles as inferred from the geometry of the bones, and robustness properties. The CT scans were used to analyse the cross-sectional and trabecular properties of the femur. Bone shape was investigated using geometric morphometrics. Phylogenetic comparative methods were utilized, e.g., to assess phylogenetic inertia and whether the independent acquisition of a fossorial lifestyle is reflected in the evolution of homoplastic morphologies. Phylogenetic inertia played a neglectable role in the trait evolution. Significant differences among lifestyles as well as allometric scaling adjustments depended on the trait under consideration. For some traits, scaling differed significantly among lifestyles, although this did not appear to be the rule. Morphological homoplasy was unlikely among the fossorial groups. The results suggest a complex, but adaptive evolutionary history of these skeletal elements in Sciuromorpha.

<p>Тема докторске дисертације је развој и верификација новог динамичког<br />модела трофазне кавезне асинхроне машине, који је заснован на<br />методи коначних елемената. Применом линеарних магнетостатичких<br />симулација и time-harmonic нелинеарних симулација се реконструишу<br />индуктивности динамичког модела машине заснованог на вишеструко<br />спрегнутим електричним колима. Модел се затим користи у<br />истраживању феномена везаних за појаву жљебних хармоника,<br />сатурацијом индукованих хармоника, као и у развоју нове методе<br />детекције сломљних шипки у роторском кавезу.</p> / <p>Tema doktorske disertacije je razvoj i verifikacija novog dinamičkog<br />modela trofazne kavezne asinhrone mašine, koji je zasnovan na<br />metodi konačnih elemenata. Primenom linearnih magnetostatičkih<br />simulacija i time-harmonic nelinearnih simulacija se rekonstruišu<br />induktivnosti dinamičkog modela mašine zasnovanog na višestruko<br />spregnutim električnim kolima. Model se zatim koristi u<br />istraživanju fenomena vezanih za pojavu žljebnih harmonika,<br />saturacijom indukovanih harmonika, kao i u razvoju nove metode<br />detekcije slomljnih šipki u rotorskom kavezu.</p> / <p>Topic of this thesis is development and verification of the novel dynamical<br />model of the three phase squirrel-cage induction machine, which is based on<br />the finite elements method. Linear magnetostatic simulations and nonlinear<br />time-harmonic simulations are used for calculation of the inductances of the<br />dynamic model of the machine based on the moultiple coupled circuit<br />approach. Model is then used for investigation of the rotor slot harmonics,<br />saturation induced harmonics and in the development of the novel method<br />for broken rotor bars detection.</p>

Orientador: Dr. Alfeu J. Sguarezi Filho / Dissertação (mestrado) - Universidade Federal do ABC, Programa de Pós-Graduação em Engenharia Elétrica, 2015. / Neste trabalho apresenta-se uma configuração do sistema de armazenamento de energia com baterias aplicado a sistemas de geração de energia eólica empregando conversores de fonte Z conectados à rede elétrica. Os geradores de indução gaiola de esquilo, são frequentemente utilizados nos sistemas de geração de energia eólica, por sua robustez, simplicidade, peso menor e custo baixo. Este é conectado diretamente ao conversor de potência bidirecional back to back, pode fornecer potências ativa e reativa à rede elétrica. Além disso, é estudado o conversor de fonte Z aplicado nesta topologia. No entanto, a implantação de sistemas de armazenamento de energia com baterias nos sistemas de geração de energia eólica na atualidade é muito importante, devido à possibilidade de oscilações da tensão e corrente na rede elétrica, portanto, estes podem ajudar à estabilização das tensões, correntes e a frequência na rede elétrica. Este sistema é conectado ao conversor back to back por meio de um conversor elevador-abaixador de corrente contínua. Para controlar a velocidade no eixo do rotor no gerador de indução, a estratégia é baseada no controle direto de torque. Enquanto, para o conversor do lado da rede é empregada a técnica de controle orientado pela tensão. Para o banco de baterias é utilizado o controle da tensão no barramento de corrente contínua e do fluxo na corrente da bateria, utilizando controladores do tipo PI. Com os novos desenvolvimentos tecnológicos nas chaves de potência, são apresentadas topologias de conversores CC-CA como o conversor de fonte Z, este tipo de conversor corrige algumas limitações do conversor back to back, com as características de elevador/abaixador de tensão, sem o uso de dispositivos de comutação, são permitidos os curto-circuitos na chaves, empregando novas técnicas de modulação, e reduz a quantidade harmônica injetada na rede elétrica. Os estudos foram realizados por meio de técnicas de simulação computacional usando modelos matemáticos do sistema estudado para a validação das estratégias de controle empregadas em diferentes condições de operação. Para as simulações empregou-se a ferramenta computacional SimPowerSystems R do Matlab/Simulink R . / This paper presents a battery energy storage system applied to wind power generation based on Z-source inverter connected to the power grid. The squirrel cage induction generators, often used in wind power generation systems, for its robustness, simplicity, lower weight and low cost. This is connected directly to the bidirectional power converter back to back, therefore, and provides active and reactive powers to grid. In addition, it is studied the Z-source inverter applied in this topology. However, the implementation of battery energy storage systems in wind power generation systems, currently is very important, due to possibility of the voltage and current fluctuations in the power grid, so these may to stabilisation of current, voltage and frequency on the grid. This system is connected to back to back converter through a DC-DC converter (buck-boost). For the rotor speed control on induction generator, the strategy is based on direct torque control. While, for the grid side converter is employed the technique of voltage oriented control. For the battery bank voltage control is used on DC-link voltage and battery current flow, through PI type controllers. With the new technological developments in the keys of power, DC converters topologies are presented as the Z-source inverter, this type converter fixes some limitations of the converter back to back, with the characteristics of buck-boost voltage, without the use of switching devices, allowed short-circuits on converter, using new modulation techniques, and reduces the amount injected harmonic to power grid. The studies were performed by means of computer simulation techniques using mathematical models of studied system to validate the control strategies employed in different operating conditions. For the simulations was used the computational tool SimPowerSystems R do Matlab/Simulink R .

Made available in DSpace on 2014-12-17T14:56:08Z (GMT). No. of bitstreams: 1 ValciFV_TESE.pdf: 3670403 bytes, checksum: d8b060478983488207d8885853eac60d (MD5) Previous issue date: 2012-11-05 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / Electrical Motors transform electrical energy into mechanic energy in a relatively easy way. In some specific applications, there is a need for electrical motors to function with noncontaminated fluids, in high speed systems, under inhospitable conditions, or yet, in local of difficult access and considerable depth. In these cases, the motors with mechanical bearings are not adequate as their wear give rise to maintenance. A possible solution for these problems stems from two different alternatives: motors with magnetic bearings, that increase the length of the machine (not convenient), and the bearingless motors that aggregate compactness. Induction motors have been used more and more in research, as they confer more robustness to bearingless motors compared to other types of machines building with others motors. The research that has already been carried out with bearingless induction motors utilized prototypes that had their structures of stator/rotor modified, that differ most of the times from the conventional induction motors. The goal of this work is to study the viability of the use of conventional induction Motors for the beringless motors applications, pointing out the types of Motors of this category that can be more useful. The study uses the Finite Elements Method (FEM). As a means of validation, a conventional induction motor with squirrel-cage rotor was successfully used for the beringless motor application of the divided winding type, confirming the proposed thesis. The controlling system was implemented in a Digital Signal Processor (DSP) / Motores el?tricos transformam energia el?trica em energia mec?nica com relativa facilidade. Em algumas aplica??es particulares, necessita-se de motores el?tricos para trabalhar com flu?dos sem contamina??o, em regime de altas velocidades, em condi??es in?spitas, ou, ainda, em locais de dif?cil acesso e ? profundidade bastante consider?vel. Nestes casos, os motores com mancais mec?nicos, cujo desgaste ocasiona a necessidade de manuten??es, n?o s?o adequados. Uma solu??o poss?vel para este problema adv?m de duas alternativas: motores com mancais magn?ticos, que t?m o inconveniente de aumentar o comprimento da m?quina, e motores-mancais, que agregam compacidade. Motores de indu??o t?m sido cada vez mais utilizados em pesquisas, pois conferem maior robustez aos motores-mancais comparados a esses tipos de m?quinas constru?das com outros motores. As pesquisas j? realizadas com motores-mancais de indu??o utilizaram prot?tipos, cujas estruturas do estator e/ou rotor foram modificadas, diferindo em grande parte dos motores de indu??o convencionais. ? objetivo deste trabalho, estudar a viabilidade do uso dos motores de indu??o convencionais para a aplica??o de motores-mancais, apontando os tipos de motores dessa categoria que mais se ad?quam. O estudo utiliza o M?todo dos Elementos Finitos FEM. Como comprova??o, um motor de indu??o convencional com rotor gaiola de esquilo foi utilizado com sucesso para a aplica??o de motor-mancal do tipo enrolamento dividido, ratificando a tese proposta. O sistema de controle foi implementado em um Processador Digital de Sinais DSP

<p>Greater prairie-chickens (<i>Tympanuchus cupido pinnatus</i>; GPC) have declined throughout large areas in the eastern portion of their range. I used species distribution modeling to predict most appropriate areas of translocation of GPC in and around Kankakee Sands, a tallgrass prairie in northwest Indiana, USA. I used MaxEnt for modelling the predictions based on relevant environmental predictors along with occurrence points of 54 known lek sites. I created four models inspired by Hovick et al. (2015): Universal, Environmental, Anthropogenic-Landcover, and Anthropogenic-MODIS. The Universal, Environmental, and Anthropogenic-MODIS models possessed passable AUC scores with low omission error rates. However, only the Universal model performed better than the null model according to binomial testing. I created maps of all models with passing AUC scores along with an overlay map displaying the highest predictions across all passing models. MaxEnt predicted high relative likelihoods of occurrence for the entirety of Kankakee Sands and many areas in the nearby landscape, including the surrounding agricultural matrix. With implementation of some management suggestions and potential cooperation with local farmers, GPC translocation to the area appears plausible.</p> <p>Franklin’s ground squirrels (<i>Poliocitellus franklinii</i>; FGS) have declined throughout a large portion of the eastern periphery of their range. Because of this, The Nature Conservancy is interested in establishing a new population of these animals via translocation. The area of interest is tallgrass prairie in northwest Indiana, USA: Kankakee Sands and the surrounding landscape. Species distribution modelling can help identify areas that are suitable for translocation. I used MaxEnt, relevant environmental variables, and 44 known occurrence points to model the potential for translocation of FGS to Kankakee Sands and the surrounding area. I created four models inspired by Hovick et al. (2015): Universal, Environmental, Anthropogenic-Landcover, and Anthropogenic-MODIS. I created maps of models with passing AUC scores. The final map was an overlay map displaying the highest relative likelihood of occurrence predictions for the area in all passing models. Only the Universal and Anthropogenic-MODIS models had passable AUC scores. Both had acceptable omission error rates. However, none of the models performed better than the null model (p < 0.05). MaxEnt predicted that a few areas in and outside of Kankakee Sands possess high relative likelihoods of occurrence of FGS in both the Universal and Anthropogenic-MODIS models. However, MaxEnt predicted high relative likelihoods in the surrounding agricultural matrix in the Universal Model. FGS prefer to cross through agricultural areas via unmowed roadside instead of open fields (Duggan et al. 2011). Because of this, high predictions in agricultural matrices in the Universal model are irrelevant. High relative likelihood predictions for linear sections that are obviously roads are disregardable in the context of my modeling efforts. Because of my low sample size, none of the models are really reliable in predicting relative likelihoods of occurrence for this area. Despite high relative likelihood predictions, the appropriateness of a translocation effort to the area is inconclusive.</p>