Mannheim, Univ., Diss., 2005.

Το αντικείμενο της παρούσας διπλωματικής εργασίας είναι η κατασκευή ενός πλήρους αυτοματοποιημένου συστήματος παραγωγής και παροχής ηλεκτρικών τάσεων με τη χρήση Προγραμματιζόμενου Λογικού Ελεγκτή (PLC) και συστήματος εποπτικού ελέγχου και συλλογής πληροφοριών (SCADA). Το σύστημα βρίσκεται στο Εργαστήριο Ηλεκτρομηχανικής Μετατροπής Ενέργειας του τμήματος Ηλεκτρολόγων Μηχανικών και Τεχνολογίας Υπολογιστών. Ο αρχικός σχεδιασμός και υλοποίηση του συστήματος έγινε το 1987 από την εταιρία ΑSEA BROWN BOVERI (ABB). Με την πάροδο του χρόνου εμφανίστηκαν βασικά λειτουργικά προβλήματα τα οποία σε συνδυασμό με την ανύπαρκτη τεχνική υποστήριξη οδήγησαν στην προβληματική λειτουργία και σταδιακά στην κατάρρευση του συστήματος. Στην πορεία λειτούργησαν κάποιες παροχές (Ε1 και Ε3) μέσω κονσόλας κλασικού αυτοματισμού με μπουτόν. Έτσι, με την πρωτοβουλία του Καθηγητή Δρ. -Μηχανικού κου Αθανασίου Ν. Σαφάκα ανατέθηκαν 7 διπλωματικές εργασίες σε φοιτητές του Τμήματος Ηλεκτρολόγων Μηχανικών και Τεχνολογίας Υπολογιστών του Πανεπιστημίου Πατρών, οι οποίες είχαν ως στόχο την επαναλειτουργία του αρχικά αυτοματοποιημένου συστήματος, με χρήση Προγραμματιζόμενων Λογικών Ελεγκτών τελευταίας γενιάς. Για την πραγματοποίηση του έργου αυτού, το σύστημα μελετήθηκε εκτενώς, καταγράφηκαν όλα τα στοιχεία του και επαναλειτούργησε, σταδιακά, σε τρεις φάσεις ανάθεσης διπλωματικών εργασιών. Συγκεκριμένα πρόκειται για την παραγωγή 10 διαφορετικών τύπων τάσεων σε 12 εργαστηριακές θέσεις. Στην 3η φάση υλοποίησης και ολοκλήρωσης του έργου, όπου εντάσσεται και αυτή η διπλωματική, υλοποιήθηκαν οι εξής παροχές: • Ε6 = 0V…230V DC • Ε7 = 0V…230V DC • Ε8 = 0V…500V DC • Ε9 = 149V…450V DC • Ε10 = 150V…500V AC, 15…100Hz Πρόκειται για μεταβλητές τάσεις που παράγονται από ζεύγη ηλεκτρικών μηχανών. Οι μηχανές αυτές βρίσκονται στο υπόγειο του Εργαστηρίου Ηλεκτρομηχανικής Μετατροπής Ενέργειας και ο χειρισμός τους γίνεται από ένα φιλικό ως προς το χρήστη περιβάλλον μέσω ηλεκτρονικού υπολογιστή (σύστημα SCADA). Ο χειριστής δεν χρειάζεται να έχει ιδιαίτερες γνώσεις για να λειτουργήσει το όλο σύστημα διότι δεν έρχεται σε άμεση επαφή με τον Προγραμματιζόμενο Λογικό Ελεγκτή (PLC) , ο οποίος είναι υπεύθυνος για την σωστή λειτουργία του συστήματος. Ο χειριστής έρχεται μόνο σε επαφή με το σύστημα SCADA , το οποίο βασίζεται στο πρόγραμμα του PLC για να λειτουργήσει. Έτσι το σύστημα που υλοποιήθηκε παρέχει ασφαλιστικές δικλείδες για την αυτόματη αντιμετώπιση οποιουδήποτε είδους σφάλματος παρουσιαστεί (υλικού αλλά και χειρισμού) , προειδοποιητικά μηνύματα και καταγραφή ιστορικού βλαβών. Ουσιαστικά προλαμβάνει και αντιμετωπίζει το σφάλμα αλλά και το λάθος του χειριστή αυτόματα και ταχύτατα. Κάποια μέρη της εργασίας με ιδιαίτερο ενδιαφέρον είναι: για την διεκπεραίωση της παροχής Ε9 γίνεται παραλληλισμός σύγχρονης γεννήτριας στο δίκτυο αυτόματα μέσω του Προγραμματιζόμενου Λογικού Ελεγκτή. Επίσης δημιουργήθηκε ένας ομαλός εκκινητής (soft starter) για έλεγχο ασύγχρονης μηχανής εκμεταλλευόμενοι την παροχή Ε10. Όλες οι παροχές μπορούν να δοθούν στους εργαστηριακούς πάγκους για εκπαιδευτικούς αλλά και ερευνητικούς σκοπούς. Στην διπλωματική γίνεται εκτενή αναφορά στις παραπάνω παροχές ,στις συνδεσμολογίες που κάναμε ,στον προγραμματισμό του PLC καθώς και στο σύστημα SCADA που έρχεται σε επαφή ο χειριστής. / This diploma thesis’ objective was to create a fully automated electrical voltage production and supply system using Programmable Logical Controller (PLC) and Supervisory Control and Data Acquisition (SCADA). This system is located in the Electromechanical Energy Conversion Laboratory of Electrical and Computer Engineering Department. The initial design and implementation of the system was in 1987 by ΑSEA BROWN BOVERI (ABB). The basic operational problems combined with little technical support led to the insufficient operation and gradually to the collapse of the system. Some supplies (E1 and E3) operated later on, using typical automation control with button console. So, Professor Dr.-Ing. Athanasios N. Safacas initiated the reoperation of the automated system with the use of new PLCs. For this purpose he assigned seven diploma thesis to the students of Electrical and Computer Engineering Department. To complete the project, the system had to be fully analyzed and its components fully registered. The project was finalized after three phases. The system includes 10 different types of electrical voltage in 12 different laboratory locations. During the third phase, that this diploma thesis is part of, the following supplies needed to be implemented : • Ε6 = 0V…230V DC • Ε7 = 0V…230V DC • Ε8 = 0V…500V DC • Ε9 = 149V…450V DC • Ε10 = 150V…500V AC, 15…100Hz These are variable voltage that are produced by electrical machine pairs. The machine are located at the basement of Electromechanical Energy Conversion Laboratory and they are operated by SCADA. The system is operated exclusively by SCADA ,so the operator doesn’t need to have special knowledge of the whole system. The system is secured against any error (hardware or operation) and offers warning messaging and saves error history. Some sections of great interest are: • The E9 supply operates through parallelism of synchronous generator with the energy network. This is achieved auto by the Programmable Logical Controller. • The E10 supply was used to provide a soft starter simulation in order to control the speed of asynchronous machine. In the diploma thesis includes all the information about the power supplies, the connections that were made, the PLC programming and the making of the SCADA system.

Η παρούσα διπλωματική εργασία πραγματεύεται τη μελέτη μίας διάταξης ανεμογεννήτριας 1kW με σύγχρονη μηχανή μόνιμων μαγνητών και με ανορθωτική γέφυρα διόδων στην έξοδό της καθώς και τη διασύνδεση αυτής με το εναλλασσόμενο δίκτυο χαμηλής τάσης. Επιπρόσθετα πραγματεύεται την κατασκευή του ανυψωτή τάσης που ενσωματώνεται στην εν λόγω τοπολογία. Η εργασία αυτή εκπονήθηκε στο Εργαστήριο Ηλεκτρομηχανικής Μετατροπής Ενέργειας του Τμήματος Ηλεκτρολόγων Μηχανικών και Τεχνολογίας Υπολογιστών της Πολυτεχνικής Σχολής του Πανεπιστημίου Πατρών. Απώτερος σκοπός της εργασίας είναι η συνολική κατασκευή μίας διάταξης δύο βαθμίδων για τη διασύνδεση της ανεμογεννήτριας με το δίκτυο χαμηλής τάσης. Οι διατάξεις αυτές περιλαμβάνουν μια πρώτη βαθμίδα ανύψωσης της τάσης της ανεμογεννήτριας μέσω της οποίας εκτελείται ένας αλγόριθμος εύρεσης του σημείου μέγιστης ισχύος της ανεμογεννήτριας (MPPT) και μια δεύτερη βαθμίδα που μετατρέπει τη συνεχή τάση σε εναλλασσόμενη (αντιστροφέας) και διατηρεί σταθερή την τάση στον πυκνωτή διασύνδεσης που παρεμβάλλεται μεταξύ των δύο βαθμίδων με έλεγχο της ενεργού ισχύος που εγχέει στο δίκτυο, ενώ παράλληλα παράγει ρεύμα συμφασικό με την τάση του δικτύου (μοναδιαίος συντελεστής ισχύος). Η πρώτη βαθμίδα αποτελεί αντικείμενο της παρούσας διπλωματικής εργασίας, ενώ η δεύτερη υλοποιήθηκε στα πλαίσια της διπλωματικής εργασίας του συναδέλφου Γ. Πυρρή. Αρχικά παρουσιάζονται τα πλεονεκτήματα και οι δυσκολίες στην εκμετάλλευση ανανεώσιμων πηγών ενέργειας και ιδιαίτερα της αιολικής, ενώ παρατίθενται και συγκρίνονται οι τεχνολογίες διασύνδεσης ανεμογεννητριών στο δίκτυο χαμηλής, μέσης και υψηλής τάσης στοχεύοντας στο να δοθεί στον αναγνώστη μια σφαιρική άποψη του υπό μελέτη θέματος. Στη συνέχεια παραθέτουμε μια θεωρητική ανάλυση όλων των εμπλεκομένων μονάδων της τοπολογίας. Ιδιαίτερη βαρύτητα δίνεται στην ανάλυση της λειτουργίας του ανυψωτή τάσης. Επόμενο βήμα αποτέλεσε η διαστασιολόγηση ολόκληρου του υπό μελέτη συστήματος, η μελέτη μεθόδων ελέγχου μέγιστης απομάστευσης ισχύος και η προσομοίωση του συστήματος. Τέλος αναλύουμε τη διαδικασία υλοποίησης του ανυψωτή τάσης και παραθέτουμε παλμογραφήματα και μετρήσεις που προέκυψαν από τα πειράματα που διενεργήσαμε μετά την ολοκλήρωση της κατασκευής σε εργαστηριακό περιβάλλον. / The current thesis deals with the study of a module of a wind generator 1kW with a synchronous permanent magnet machine and a diode rectifier in its output and its interconnection to the low voltage AC grid. Furthermore the thesis deals with the construction of the boost converter that is connected to this topology. This thesis was conducted in the Laboratory of Electromechanical Energy Conversion, Department of Electrical and Computer Engineering School of Engineering, University of Patras. The outer purpose of this study is the construction of a two-stage topology for the interconnection of the wind genereator to the low voltage grid. The topology consist of a first stage that boosts the voltage of the wind generator while a maximum power point tracking algorithm (MPPT) is executed and of a second stage that converts the direct voltage to alternative (inverter) and maintains the voltage of the link capacitor that is between the two stages with control of the active power that is injected to the grid, while producing current that has the same phase as the voltage grid (unitary power coefficient). The first stage is object of the current thesis, while the second was constructed in the thesis of workmate G.Pyrris. Initially, are represented the advandages and disadvantages of the utilization of the renewable energy sources and especially the wind energy, while different technologies for interpolation of wind generators to the low, medium and high voltage grid are represented and compared in order to give to the reader a global idea of the subject. Consequently a theoretical analysis of all the related modules is cited. Special reference was given to the analysis of the boost converter. Next step was the dimensioning of the whole system, the study of maximum power point tracking methods and the simulation of the system. Finally, the procedure of the boost converter’s construction is elaborated and pulse waves and measurements that were extracted during the experiments that were conducted in laboratory environment are represented .

Thesis (MSc)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: The design optimisation of a linear oscillatory electric generator for application in freepiston Stirling engines is described in this thesis. A basic overview of free-piston Stirling engine technology is given by firstly providing a brief description of the operation of the heat engine. The applications of free-piston Stirling engines in industry are given and the proposed future applications are described. Different types of electrical machine designs from industry and academia are evaluated in a literature study. A classification structure is also proposed based on the magnetic flux variation within the designs. Based on the literature study, a transverse flux, single-phase, moving magnet, tubular topology was chosen for investigation. Athree dimensional finite element simulation was chosen as the most appropriatemethod to model the linear electrical machine. A commercial simulation package was called from a simulation script and the outputs from the finite element simulation were again used to calculate the electrical machine performance parameters using the instantaneous voltageand current values. A sequential quadratic programming algorithm was used to perform optimisation of the machine topologies, with the optimisation variables being dimensional parameters that describe the machine geometry and the goal of the optimisation to minimise the active mass of the machine, while maintaining preset minima for the output power and the efficiency. The machine was optimised for a number of different translator configurations and the different configurations were analysed and compared. It was found that a quasi-Halbach arrangement of the permanent magnets yielded the lowest overall active mass. A comparative study is also presented, where this quasi-Halbach variant is compared to a commercial machine. It was found that the linear machine design with a quasi-Halbach arrangement compares well with the commercial machine. A prototype and test bed was designed and constructed. Due to manufacuring difficulties however, the machine could not be completed in time for testing. / AFRIKAANSE OPSOMMING: Die ontwerpsoptimering van ’n lineêre ossillerende elektriese generator vir toepassing in vrysuier Stirling enjins word beskryf in hierdie tesis. ’n Basiese oorsig van vrysuier Stirling enjin tegnologie word gegee deur eerstens ’n kort beskrywing te gee van die werking van die hitte-enjin. Die aanwending van vrysuier Stirling enjins in industrie word gegee en voorgestelde toekomstige toepassings word beskryf. Verskillende tipes elektriese masjien ontwerpe vanuit die industrie en die akademie word geëvalueer in ’n literatuurstudie. ’n Klassifiseringstruktuur, gebaseer op die magnetiese vloedverandering in die ontwerpe, word ook voorgestel. ’n Transverse vloed, enkelfase, bewegende magneet, tubulêre topologie is gekies vir die ondersoek, gebaseer op die onder andere die literatuurstudie. ’n Drie-dimensionele eindige element simulasie is gekies as die mees geskikte metode om die lineêre elektriese masjien te modelleer. ’n Kommersiële simulasie pakket is deur middel van ’n simulasie skrip geroep en die uitsette vanaf die eindige element simulasie is weer gebruik om die werksverrigtingsparameters van die elektriese masjien te bereken deur gebruik te maak van die oomblikswaardes van die spanning en stroom. ’n Sekwensiële kwadratiese programmering algoritme is gebruik om optimering van die masjien topologieë te doen, met die dimensionele parameters wat die masjien geometrie beskryf as die optimeringsveranderlikes en doel van die optimering om die aktiewe massa van die masjien te minimeer, terwyl die uitsetdrywing en die benuttingsgraad by voorafgestelde minima gehou word. Die masjien is geoptimeer vir verskeie translator konfigurasies en die verskillende konfigurasies is geanaliseer en vergelyk. Dit is bevind dat ’n kwasi-Halbach skikking van die permanente magnete die laagste totale aktiewe massa gelewer het. ’n Vergelykende studie is ook aangebied, waar die kwasi-Halbach variant vergelyk is met ’n kommersiële masjien. Dit is bevind dat die lineêre masjien met die kwasi-Halbach skikking baie goed vergelyk met die kommersiële masjien. ’n Prototiepe masjien en toetsopstelling is ontwerp en aan mekaar gesit. Maar as gevolg van vervaardigbaarheids tekortkominge kon toetse op die prototiepe nie betyds gedoen word nie.

Orientador: Laurence Duarte Colvara / Banca: Dionizio Paschoareli Junior / Banca: Walmir de Freitas Filho / Resumo: Propõe-se neste trabalho o desenvolvimento de uma metodologia analítica para análise do desempenho dinâmico/transitório dos geradores de indução conectados ao sistema de energia elétrica. O método proposto para o estudo da estabilidade das máquinas de indução baseia-se no monitoramento da tensão interna E' durante o período transitório do sistema, a qual pode comprometer a capacidade de transmissão de potência na linha, com consequente colapso da estabilidade da máquina. Deste modo, faz-se a análise do desempenho transitório da máquina pela observação da grandeza em que efetivamente reside a causa da instabilidade. O método desenvolvido foi validado por meio de simulações digitais, em duas configurações do sistema: o primeiro caso, desprezando o suporte de potência reativa, para efeito de análise nos estudos de estabilidade transitória. No segundo, é realizada a compensação dinâmica de potência reativa via SVC (Static Var Compensator). Neste caso, mesmo na presença do compensador variável de reativo, o método da tensão interna revelou-se capaz de avaliar novos limites de estabilidade para o sistema. Considerados os resultados obtidos, observa-se que o método proposto apresenta resultados suficientemente precisos para avaliar o comportamento dos geradores de indução conectados à rede elétrica / Abstract: This dissertation proposes the development of an analytical methodology for analysis of dynamic/transient performance of an induction generator connected to a bulk power system. The proposed method for studying the stability of induction machines is based on monitoring the internal voltage named E' since during the transient system, its magnitude may decrease and so causing degeneration of the transmission system capability, with consequent collapse of machine stability. Thus it is the analysis of transient performance of the machine by observing the variable that is actually the cause of instability. The analytical method was validated by means of digital simulations, in two system configurations: in the first case, no reactive support is considered, and the purpose is to analyse the machine transient stability itself. In the second, a reactive support is provided by means of the dynamic reactive compensation via SVC (Static Var Compensator). In this case, even in the presence of variable reactive compensator, the method of internal voltage proved to be able to properly assess new stability limits. The results so obtained lead to the indication that the proposed method results are accurate enough in order to evaluate the behavior of induction generators, connected to the power grid

Le travail de cette thèse vise la réalisation d’un nouveau capteur d’images pour mobile en technologie CMOS (Complementary Metal Oxide Semiconductor). Ce capteur a été développé en vue de répondre à une forte demande du marché. Les prochaines générations de produits, nécessitent des capteurs d’image avec des performances agressives. Par exemple, le niveau de qualité d’image peut être fortement amélioré avec des architectures faible bruit, ou l’utilisation de nouvelles technologies, pour augmenter le niveau du signal ou diminuer la consommation. L’augmentation de la qualité d’image entraîne un agrandissement de la taille des matrices de pixels, et de la résolution des données. La vitesse de conversion devient donc critique. Le sujet de cette thèse porte sur l’amélioration de ce dernier point. Une étude comparative a été réalisée pour étudier différentes architectures. Le convertisseur à rampe est le mieux adapté pour les petits pixels. Toutefois, son principal inconvénient est son temps de conversion qui nécessite 2N cycles d’horloge. Afin d’obtenir un frame rate plus élevé, une méthode tirant profit du bruit photonique a été proposée. Ce circuit de lecture est fondé sur un convertisseur à rampe par morceaux, et un algorithme qui permet la linéarisation des données. Afin de réduire le bruit, cette nouvelle architecture doit prendre en compte le double échantillonnage corrélé digital. Durant la période de conception, des modes de test ont été mis en place pour permettre la caractérisation du circuit. L’innovation se trouve dans le développement d’une rampe par morceaux qui réduit le temps de lecture d’une ligne de 1us. Cependant, ce développement a besoin d’une calibration adaptée. Un prototype de capteur d’image CMOS de 13Mpixel a été fabriqué en 65 nm, 5 niveaux de métaux, et 1 seul niveau de poly en technologie CMOS standard. Les mesures ont montré que l’INL et DNL du convertisseur étaient aussi performantes qu’avec une rampe linéaire classique. Une attention particulière a été apportée sur la mesure du bruit. Malheureusement, le bruit s’est montré plus élevé qu’avec un capteur « classique ». Cependant, la consommation reste identique en ayant une vitesse de conversion plus rapide. Les solutions proposées sont simples à intégrer structurellement, et faciles à mettre en œuvre. Elles ont l’avantage de ne pas impacter la surface du pixel et préservent donc les performances de ce dernier. Les résultats issus des mesures sur silicium sont très encourageants, car on obtient un gain de presque 20% sur le temps de lecture. / The aim of this thesis is the implementation of new image sensors for mobile in CMOS (Complementary Metal Oxide Semiconductor) technology to meet strong market demand. Next generations of products require image sensors with high performances.These improvements would change the image quality with low noise architecture in one hand, and the use of new technologies to increase the signal level, or reduce the power consumption in the other hand. The gain in image quality leads to increase the size of the pixel’s array, and the resolution of the data -the conversion speed becoming critical-. The subject of this thesis focuses on improving this latter point. A comparative study has been made between several architectures to find the best solution that would fit our needs.The ramp converter is the most suitable for small pixels, but his main drawback is the conversion time that requires 2N clock cycles. To obtain a higher frame rate, a method taking advantage of the photon noise has been presented. This readout circuit is based on a piecewise linear ramp converter and an algorithm that allows the linearization of the data. Furthermore, for noise reduction, the new architecture must take into account the digital correlated double sampling. During the period of design, test modes have also been designed and implemented to allow characterization of the circuit.The innovative part is the use of a piecewise linear ramp, which in simulation, reduces the readout time of 1us per row. However, this element needs calibration. A CMOS image sensor prototype of 13Mpixel has been made in 65 nm, 5 levels of metals, and 1 level of poly standard CMOS technology. Measurements showed that the INL and DNL of the converter were as good as with a conventional linear ramp. A careful consideration has been given to the measurement of noise, which unfortunately is higher than a "conventional" sensor. However, the consumption remains the same while having a faster conversion speed. The solutions are simple to integrate structurally and easy to implement. They have the advantage of not affecting the surface of the pixel, thus preserve the performance of the latter. The results found from the silicon-on measures are very encouraging, we gain almost 20% of the conversion time.

abstract: An advantage of doubly fed induction generators (DFIGs) as compared to conventional fixed speed wind turbine generators is higher efficiency. This higher efficiency is achieved due to the ability of the DFIG to operate near its optimal turbine efficiency over a wider range of wind speeds through variable speed operation. This is achieved through the application of a back-to-back converter that tightly controls the rotor current and allows for asynchronous operation. In doing so, however, the power electronic converter effectively decouples the inertia of the turbine from the system. Hence, with the increase in penetration of DFIG based wind farms, the effective inertia of the system will be reduced. With this assertion, the present study is aimed at identifying the systematic approach to pinpoint the impact of increased penetration of DFIGs on a large realistic system. The techniques proposed in this work are tested on a large test system representing the Midwestern portion of the U.S. Interconnection. The electromechanical modes that are both detrimentally and beneficially affected by the change in inertia are identified. The combination of small-signal stability analysis coupled with the large disturbance analysis of exciting the mode identified is found to provide a detailed picture of the impact on the system. The work is extended to develop suitable control strategies to mitigate the impact of significant DFIG penetration on a large power system. Supplementary control is developed for the DFIG power converters such that the effective inertia contributed by these wind generators to the system is increased. Results obtained on the large realistic power system indicate that the frequency nadir following a large power impact is effectively improved with the proposed control strategy. The proposed control is also validated against sudden wind speed changes in the form of wind gusts and wind ramps. The beneficial impact in terms of damping power system oscillations is observed, which is validated by eigenvalue analysis. Another control mechanism is developed aiming at designing the power system stabilizer (PSS) for a DFIG similar to the PSS of synchronous machines. Although both the supplementary control strategies serve the purpose of improving the damping of the mode with detrimental impact, better damping performance is observed when the DFIG is equipped with both the controllers. / Dissertation/Thesis / Ph.D. Electrical Engineering 2010

A teoria de duplo eixo é geralmente utilizada para modelar e caracterizar máquinas síncronas de polos salientes. O conhecimento das indutâncias de eixo direto e eixo em quadratura são fundamentais para o desenvolvimento destes modelos e para o projeto de controladores destas máquinas. No entanto, métodos tradicionais para determinação destas indutâncias através de ensaios tornam-se impraticáveis em máquinas síncronas de ímãs permanentes pela impossibilidade de controlar a corrente de campo. Recentemente, a IEEE publicou o Std. 1812, chamado Trial-Use Guide for Testing Permanent Magnet Machines, que pode servir de guia para obtenção da reatância de eixo direto Xd. Esta norma não sugere formas de determinar a reatância de eixo em quadratura Xq, mas existem diferentes métodos para calcular este parâmetro a partir de dados coletados em testes, geralmente envolvendo medição de ângulo de carga. O objetivo deste trabalho é propor e analisar dois métodos alternativos para determinar as reatâncias do modelo de duplo eixo através de ensaios aplicados a um gerador síncrono de ímãs permanentes (GSIP) de 1,5 kW. O primeiro é baseado em predição de ângulo de carga e o segundo é baseado em medição de ângulo de carga. O primeiro combina ensaios a vazio e de curto circuito com análise do diagrama fasorial para descrever o ângulo de carga como função de grandezas elétricas facilmente mensuráveis. O segundo propõe um método de medição de ângulo de carga com auxílio de um encoder incremental. Resultados comprovam que é possível determinar indutâncias do modelo de duplo eixo com as equações desenvolvidas desde que o conteúdo harmônico não seja elevado. / A teoria de duplo eixo é geralmente utilizada para modelar e caracterizar máquinas síncronas de polos salientes. O conhecimento das indutâncias de eixo direto e eixo em quadratura são fundamentais para o desenvolvimento destes modelos e para o projeto de controladores destas máquinas. No entanto, métodos tradicionais para determinação destas indutâncias através de ensaios tornam-se impraticáveis em máquinas síncronas de ímãs permanentes pela impossibilidade de controlar a corrente de campo. Recentemente, a IEEE publicou o Std. 1812, chamado Trial-Use Guide for Testing Permanent Magnet Machines, que pode servir de guia para obtenção da reatância de eixo direto Xd. Esta norma não sugere formas de determinar a reatância de eixo em quadratura Xq, mas existem diferentes métodos para calcular este parâmetro a partir de dados coletados em testes, geralmente envolvendo medição de ângulo de carga. O objetivo deste trabalho é propor e analisar dois métodos alternativos para determinar as reatâncias do modelo de duplo eixo através de ensaios aplicados a um gerador síncrono de ímãs permanentes (GSIP) de 1,5 kW. O primeiro é baseado em predição de ângulo de carga e o segundo é baseado em medição de ângulo de carga. O primeiro combina ensaios a vazio e de curto circuito com análise do diagrama fasorial para descrever o ângulo de carga como função de grandezas elétricas facilmente mensuráveis. O segundo propõe um método de medição de ângulo de carga com auxílio de um encoder incremental. Resultados comprovam que é possível determinar indutâncias do modelo de duplo eixo com as equações desenvolvidas desde que o conteúdo harmônico não seja elevado.

Os ROBDDs são estruturas utilizadas com sucesso em ferramentas de CAD para microeletrônica. Estas estruturas permitem a representação canônica de funções booleanas ao se estabelecer um ordenamento fixo de variáveis. No contexto de um gerador automático de células lógicas para circuitos integrados, os ROBDDs podem servir de base para a derivação de redes de transistores cujo comportamento elétrico equivale ao comportamento lógico de uma função booleana desejada. Nas redes de transistores derivadas de ROBDDs, o posicionamento relativo dos transistores é determinado pelo ordenamento de variáveis. O efeito do reordenamento de transistores já foi estudado na década de noventa e sabe-se de sua influência sobre características de área, atraso e potência de um circuito digital. Entretanto, estes estudos limitam-se à topologia CMOS complementar série/paralelo, que é a topologia de redes de transistores mais comum. Neste trabalho, explora-se o efeito do reordenamento de variáveis nas características de área e atraso de circuitos mapeados com seis famílias lógicas diferentes, cujas células constituem redes de transistores derivadas de ROBDDs. Em geral, os resultados dos experimentos indicam que, para estas famílias lógicas, selecionar ordenamentos, onde transistores controlados por sinais mais críticos posicionam-se relativamente mais próximos à saída da célula, pode levar ao mapeamento de circuitos com atraso 16,4% inferior, em média, ao atraso do circuito equivalente com ordenamentos selecionados para obtenção da menor área possível e ignorando-se os atrasos de chegada nas entradas de uma célula. / The ROBDDs are structures that have been successfully used in CAD tools for microelectronics. These structures allow canonical representation of boolean functions when established a fixed variable ordering. In the context of an automatic logic cell generator for integrated circuits, ROBDDs may serve as a base for deriving transistor networks from which electrical behavior is equivalent to the logic behavior of a specified boolean function. With ROBDD derived transistor networks, the relative placement of transistors is determined by variable ordering. The effect of transistor reordering was already studied in the nineties and we know about its influence over area, delay and power characteristics of an integrated circuit. However, these studies were limited to complementary series/parallel CMOS topology, which is the standard for transistor networks topology. In this work, the effect of variable reordering is explored over area and delay characteristics of circuits mapped to six different logic families, where cells are designed with ROBDD derived transistor networks. Experimental results indicate that, in general, placing transistors controlled by the most critical signals closer to cell output may lead to a circuit mapping with an average 16.4% less delay than an equivalent circuit where orderings for smallest possible area are selected and input arrival times of a cell are ignored.

Ce mémoire présente une étude sur l’usure générée par des impacts glissants obliques faiblement chargés, et plus particulièrement par les impacts répétés entre les tubes de générateur de vapeur et les barres antivibratoires dans les réacteurs à eau pressurisée. L’étude expérimentale de la dynamique des impacts obliques montre une très forte dépendance de leurs caractéristiques à l’angle d’incidence, avec l’existence de deux régimes de frottement distincts, caractérisés par du glissement pendant tout l’impact pour les angles rasants et par une phase de glissement suivi d’une phase d’adhérence pour les angles proches de la normale. Les caractéristiques dynamiques des impacts, telles que le rapport de percussion, la perte d’énergie ou la distance glissée au cours d’un impact, sont exprimées en fonction des paramètres incidents, du coefficient de frottement cinétique et du coefficient de restitution, en étendant les formulations érosives de Brach [1] au cas d’impacts percussifs multi-aspérités faiblement chargés. L’étude de l’usure générée par des impacts obliques en air et en eau à température ambiante montre que celle-ci est reliée linéairement à la perte d’énergie sans période d’incubation, par un coefficient constant en air, et par un coefficient qui dépend fortement de l’angle d’incidence en eau. Les surfaces usées présentent des stries semblables à de fines rayures d’abrasion, sans trace d’adhésion ou de déformation plastique importante, incitant à proposer un scénario d’endommagement fondé sur un enlèvement de matière uniquement généré par des micro-rayures d’abrasion. Deux modèles d’usure par impacts en eau sont formulés, exprimant d’une part le volume usé et d’autre part la profondeur usée en fonction des paramètres incidents des impacts, du coefficient de restitution, du coefficient de frottement cinétique, des caractéristiques géométriques du tube GV et de la BAV et d’un coefficient d’usure constant. / This thesis presents a study on wear induced by low-loaded sliding impacts in general and on wear induced by repetitive impacts between steam generator tubes and antivibration bars in pressurized water reactors in particular. The experimental study of the impacts dynamics shows that their characteristics strongly depend on the incidence angle. Two friction regimes are observed, characterized by sliding throughout the impact for grazing angles and by the existence of a sliding phase followed by an adhesion phase for the angles close to normal. The dynamic characteristics of the impacts, such as the impulse ratio, the energy loss or the sliding distance during an impact, are expressed as functions of the incident parameters, the kinetic friction coefficient and the restitution coefficient. These expressions extend the erosive formulations of Brach [1] to the case of low-loaded percussive multi-asperities impacts. The study of wear induced by oblique impacts at ambient temperature in air and water environment shows a linear relationship between the wear volume and the energy loss without any incubation period, with a constant proportionality coefficient in air, and with a proportionality coefficient which strongly depends on the incidence angle in water environment. Ridges similar to thin abrasion scratches are observed on the worn surfaces, without any mark of adhesion or significant plastic deformation. Thus, a damage scenario based on micro-scratching abrasion only is proposed. Two impacts wear models in water environment are proposed, which express firstly the worn volume and secondly the maximal worn depth as functions of the impacts incident parameters, the restitution coefficient, the kinetic friction coefficient, the SG tube and AVB geometrical characteristics and a constant wear coefficient.