Tesis sobre el tema "Short Circuit turn to turn"
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Babu, Hareesh. "Finite-element analysis of an induction motor with inter-turn short-circuit faults". Thesis, KTH, Skolan för elektroteknik och datavetenskap (EECS), 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-290082.
Texto completoKortslutning mellan varven i en asynkronmotors statorlindning (ITSC) är en av de vanligaste källorna för fel som påverkar dess drifttillförlitlighet. I detta examensarbete utvecklas en finit-element (FE) modell för att studera ITSC- fel. FE-modellen är utvecklad för en asynkronmotorprototyp som kan emulera ITSC-fel. Med den utvecklade modellen utförs en simuleringsstudie för att förstå beteendet hos olika elektriska och magnetiska egenskaper både i tids- och frekvensdomän. Dessa egenskaper är goda indikatorer av statorlindningsfel och kan därför med fördel användas i ett tillståndsövervakningssystem. Prototypmaskinen har testats experimentellt och de erhållna resultaten jämförs med FE-simuleringen och analysresultaten. Det analytiska resultatet, FEM- simuleringarna och den experimentella utvärderingen uppvisade god överrensstämmelse vad gäller felströmmen. Dock finns det en mindre avvikelse när det gäller amplituden hos statorströmmens negativa fasföljd. Orsaken till denna avvikelse är att prototypmaskinens geometri inte är helt känd.
Lennartsson, Alexander y Martina Blomberg. "Fault Detection in Permanent Magnet Synchronous Motors using Machine Learning". Thesis, Luleå tekniska universitet, Institutionen för system- och rymdteknik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-84909.
Texto completoOliveira, Ãtila GirÃo de. "Neural classifier aplied in stator winding inter-turn short circuit in three-phase induction motors driven by frequency converter". Universidade Federal do CearÃ, 2014. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=12285.
Texto completoThis dissertation reports applications of artificial neural networks to detect stator winding interturn fault of three phase induction motor drived by frequency inverter. The artificial neural networks, like Simple and Multilayer Perceptron, served as off-line classifiers to short-circuit fault condition or healthy condition. In the training of Multilayer Perceptron, two different algorithms are used: the error back-propagation, which is a classic algorithm, and the extreme learning machine, as a relative new alternative for the classic back-propagation. The new one is more worthwhile because of its implementation easiness and higher speed of computation. The database used on the training and validation of the networks is created from an experimental setting, therefore it is composed by true data. The attributes used as failuresâ indicators are selected from certain frequencies of the spectrum, based on some theories of current signature analysis. In the second instance, the technique of principal components analysis is employed. The results obtained for the designed classifiers are shown, and some considerations are made on their use in real time embedded applications, which is the most important projection for future researches.
Este trabalho deriva da aplicaÃÃo de redes neurais artificiais para a detecÃÃo de curto-circuito entre espiras em motor de induÃÃo trifÃsico, acionado por inversor de frequÃncia. As redes neurais artificiais, do tipo Perceptron Simples e Multicamadas, sÃo usadas para detectar falhas de curto-circuito no bobinamento estatÃrico de motores de induÃÃo trifÃsicos de forma off-line. Para treinamento do Perceptron Multicamadas sÃo usados dois algoritmos distintos: o error back-propagation, que figura como o algoritmo clÃssico na literatura especializada, e o extreme learning machine, que à uma alternativa, relativamente recente, ao algoritmo clÃssico. Este algoritmo à uma opÃÃo atraente para o desenvolvimento rÃpido de classificadores. O banco de dados usado para treinamento e validaÃÃo das redes à obtido a partir de experimentaÃÃo laboratorial, portanto composto de dados reais. Os atributos utilizados para a detecÃÃo da falha sÃo componentes de frequÃncia do espectro harmÃnico da corrente estatÃrica do motor. O critÃrio de escolha destas componentes, a priori, à fundamentado em resultados de investigaÃÃes prÃvias da assinatura de corrente e, em segunda instÃncia, à aplicada a tÃcnica de anÃlise de componentes principais. SÃo apresentados os resultados obtidospelos classificadores projetados, e feitas algumas consideraÃÃes quanto à utilizaÃÃo destes em aplicaÃÃo embarcada e em tempo real, que à a principal projeÃÃo de futuros trabalhos a partir do atual.
Ge, Yuxue. "Energy Management in More Electric Aircraft through PMSM Fault Diagnosis, Adaptive Load Shedding and Efficient Aircraft Design". Doctoral thesis, Universite Libre de Bruxelles, 2019. https://dipot.ulb.ac.be/dspace/bitstream/2013/287798/5/contratYG.pdf.
Texto completoDoctorat en Sciences de l'ingénieur et technologie
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Singh, Bhanu Pratap. "Real-time detection of stator resistance unbalances in three phase drives". Thesis, KTH, Skolan för elektroteknik och datavetenskap (EECS), 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-286813.
Texto completoUppskattningsvis 30% av alla fel i induktionsmaskiner (IM) är kopplad till dess stator. Dessa fel är i huvudsak Inter-Turn Short Circuit (ITSC)-fel, dvs. två lindningar inom IM:ens stator blir kortsluta pga. ett isoleringsfel. Emellertid kan man undvika ITSC-fel genom att detektera dem i förhand och planera underhåll. Det här examensarbetet undersöker två metoder för att detektera ett förestående ITSC-fel i en tre-fas IM. Den första metoden är baserad på asymmetrin i IM:er pga. ITSC-felet. Resultatet av den här asymmetrin är att en negativ sekvens genereras i IM:ens statorspänning och statorström. En oskadad IM kan också visa dessa negativa sekvenser pga. tillverksprocessen och statorspänningsobalanser. Egenskaperna och kompensationsmetoderna för dessa negativa sekvenser i en oskadad IM kommer att diskuteras. Resultaten visar att efter kompenseringen av de negativa sekvenserna i en oskadad IM, kan de användas för att detektera ITSC-fel och efteråt för att beräkna felstorheter och även statormotståndobalanser. Den andra metoden för att detektera ITSC-fel är baserad på en undersökning av statormotståndobalanser. Ett tre-fas-drivsystem används för att injektera likspänning i den stationära referensramen. Likströmmen som följer av denna likspänning mäts och statorfasmotstånden beräkna efteråt med Ohms lag. I en oskadad IM är fasmotstånden balanserade. Däremot, när ett ITSC-fel uppstår i en fas, avviker fasmotståndet i den felaktiga fasen från de andra två fasernas, vilket kan användas för att detektera ITSC-fel.
MacNamara, Liam. "Development of short turn coal spirals". Thesis, University of Nottingham, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.243434.
Texto completoGinzarly, Riham. "Contribution à la modélisation et au pronostic des défaillances d'une machine synchrone à aimants permanents". Thesis, Normandie, 2019. http://www.theses.fr/2019NORMR038/document.
Texto completoThe core of the work is to build an accurate model of the electrical machine where the prognostic technique is applied. In this thesis we started by a literature review on hybrid electric vehicles (HEV), the different types of electrical machine used in HEV’s and the different types of faults that may occur in those electrical machine. We also identify the useful monitoring parameters that are beneficial for those different types of faults. Then, a survey is presented where all the prognostic techniques that can be applied on this application are enumerated. The electromagnetic, thermal and vibration finite element model (FEM) of the permanent magnet machine is presented. The model is built at healthy operation and when a fault is integrated. The considered types of faults are:demagnetization, turn to turn short circuit and eccentricity. A confrontation between analytical and FEM (numerical method) for electromagnetic machine modeling is illustrated. Fault indicators where useful measured parameters forfault identification are recognized and useful features from the measured parameters are extracted; torque, temperature and vibration signal are elaborated for healthy and faulty states. The strategy of the adopted prognostic approach which is Hidden Markov Model (HMM) is explained. The technical aspect of the method is presented and the prognostic model is formulated. HMM is applied to detect and localize small scale fault small scale faults were where a systematic strategy is developed. The aging of the machine’s equipment,specially the sensitive ones that are the stator coil’s and the permanent magnet, is a very important matter for RUL calculation. An estimation strategy for RUL calculation is presented and discussed for those mentioned machine’s components. Closed loop configuration is very important; it is adopted by all available vehicle systems. Hence, the same previously mentioned steps are applied for a closed loop configuration too. A global model where the input of the machine’s FEM comes from the modeled inverter is built
Leboeuf, Nicolas. "Contribution à l'étude des machines synchrones à aimants permanents en présence de défauts inter-spires : modélisation, détection de défauts inter-spires". Thesis, Université de Lorraine, 2012. http://www.theses.fr/2012LORR0364/document.
Texto completoEmbedded electric systems in aircraft applications have to satisfy to specifications including weight, performances and reliability leading to the use of Permanent Magnet Synchronous Machines (PMSM). Due to these constraints, prototypes are often different from classical PMSM. Online monitoring of these systems is challenging but is still important regarding safety applications (electro mechanical airfoil, braking?). The main aim is to detect major incidents in order to use redundant systems. This work concerns modeling of PMSM under both healthy and inter-turn fault cases in order to defined online fault detection methods without additional sensors. Two approaches are presented and compared to experimental tests concerning PMSM under inter-turn fault conditions. One of them is based on Permeance Network (PN) modelling. It can be considered to be the best compromise. The next part deals with two fault indicators methods based on healthy models of Inverter and PMSM and shows improvements brought by these approaches compared to classical methods. The whole indicators are analyzed using Pattern Recognition (PR)
Deckoff, Anthony Adlai. "The short-turn as a real time transit operating strategy". Thesis, Massachusetts Institute of Technology, 1990. http://hdl.handle.net/1721.1/41774.
Texto completoTseng, King Jet. "Modelling of gate turn-off thyristors for use in circuit simulations". Thesis, University of Cambridge, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.308186.
Texto completoFilleau, Clément. "Mise en place d'une méthodologie de modélisation en vue du diagnostic des défauts électriques des alternateurs". Phd thesis, Toulouse, INPT, 2017. http://oatao.univ-toulouse.fr/19288/1/Filleau.pdf.
Texto completoAubert, Brice. "Détection des courts-circuits inter-spires dans les Générateurs Synchrones à Aimants Permanents : Méthodes basées modèles et filtre de Kalman étendu". Phd thesis, Toulouse, INPT, 2014. http://oatao.univ-toulouse.fr/11902/1/Aubert.pdf.
Texto completoReynolds, William Leonard. "Sustainable Service Rate Analysis at Signalized Intersections with Short Left Turn Pockets Using Macroscopic Simulation". NCSU, 2010. http://www.lib.ncsu.edu/theses/available/etd-03302010-171706/.
Texto completoAlameh, Kawthar. "Contribution au diagnostic et a l'analyse de défauts d'une machine synchrone à aimants permanents". Thesis, Normandie, 2017. http://www.theses.fr/2017NORMR072/document.
Texto completoThe advent of new magnetic materials and recent advances in power electronics have played a major role in the progress of hybrid electric vehicles. Nowadays, permanent magnet synchronous machines (PMSM) thanks to their performances, especially their energy efficiency, are considered as ideal candidates for the traction chains of hybrid and electric vehicles. However, due to material aging, manufacturing defects or severe operating conditions, different types of faults are capable to occur in the machine components, its control or measuring devices. In order to ensure safety, reliability and availability, the integration of a fault diagnosis and condition monitoring approach in the automotive electrical powertrain system is becoming more and more important. In this context, the aim of the thesis is to contribute to the diagnosis and characterization of faults in the PMSM based on a vibration analysis. First, analytical modeling approaches for the PMSM and inter-turn short-circuits, eccentricity and rotor demagnetization faults will be proposed. The major interest of such models, in a diagnosis context, is to study the behavior of the machine in the presence of studied faults in order to deduce the most suitable detection methods. In addition, numerical models will be developed in order to validate the analytical magnetic and mechanical parts of the machine as well as the demagnetization fault. In the phase of fault impact analysis, we will focus on the cases of rotor eccentricity and demagnetization. The fault indicators will be extracted from the vibratory signal representations in time and space domains and their Fourier transforms, in the cases of single faults and the cases of two combined faults. For single fault cases, two diagnosis approaches will be proposed: the first uses the principle of statistical tests and fault signature tables, inspired by model-based diagnosis methods, while the second relies on a set of three neural networks, such as each one is with a single input and a single output and dedicated to isolate one type of fault. Finally, the performance of these two approaches, in terms of robustness and adaptability, will be compared for the same training and test sets
Borra, Venkata Shesha Vamsi. "Design and Modeling of High Performance LED Dimming Driver with Reduced CurrentSpikes using Turn-On Snubber across Power MOSFET". Youngstown State University / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=ysu1402958388.
Texto completoIdrissi, Imane. "Contribution au Diagnotic des Défauts de la Machine Asynchrone Doublement Alimentée de l'Eolienne à Vitesse Variable". Thesis, Normandie, 2019. http://www.theses.fr/2019NORMR033/document.
Texto completoActually, the Doubly Fed Induction Generators (DFIG) are omnipresent in the wind power market, owing to their construction simplicity, their low purchase cost and their mechanical robustness. However, as any other electrical machine, these generators are subject to defects of different order (electrical, mechanical, electromagnetic ...) or of different type (sensor, actuator or system). That’s why, it is important to design an effective diagnostic approach, able to early detect, locate and identify any defect or abnormal behavior, which could undermine the healthy operation of this machine On the one hand, motivated by the observer-based fault diagnosis methods strengths, we proposed, in this thesis, a diagnostic approach for the faults detection, localization and identification of the DFIG used in variable speed wind turbine. This approach is based on the use of the efficient and widely used Kalman observers. The state estimation errors of the linear Kalman filter and the non-linear Kalman filters, named: The Extended Kalman Filter (EKF) and the Unscented Kalman Filter (UKF) are used as faults sensitive residuals. In order to avoid false alarms and to decouple faults from disturbances and noises, the faults detection is carried out by the analysis of the residuals generated, by the mean of statistical tests such as: Hinkley Page Test (PH) and DCS Test (Dynamic) Cumulative Sum). For the localization step in case of multiple and simultaneous faults, the Dedicated Observer scheme (DOS) and the Generalized Observer scheme (GOS) are applied. In addition, the fault level is determined in the fault identification step. Sensor faults, actuator and system faults of DFIG, are treated in this research work. On the other hand, a comparative study between the three Kalman observers proposed is performed. The comparison was done in terms of (1) the computation time, (2) the estimation accuracy, and (3) the convergence speed
Sousa, Éder Aparecido de. "Atributos de qualidade valorizados pelos consumidores de produtos agroalimentares em cadeias curtas de proximidade espacial /". Tupã, 2019. http://hdl.handle.net/11449/182504.
Texto completoResumo: No passado a qualidade era percebida como atendimento a padrões, hoje quando falamos de qualidade, remetemos ao atendimento a vários atributos, muitas vezes subjetivos ao produto ou serviço. A produção de alimentos na atualidade é dominada por um sistema de produção que vem passando por uma série de questionamentos da sociedade pela perda de valores nutricionais, pelos problemas ambientais causados, pelos impactos econômicos para o pequeno produtor e pela falta de identificação clara de quem produz. Assim, a qualidade do alimento que até então tinha como sinônimo o atendimento a padrões, vem tomando um outro significado, atrelada a valores sociais, ambientais e de localização. Sendo assim, esse trabalho identificou e analisou os atributos de qualidade valorizados por consumidores que adquirem produtos em cadeias curtas de proximidade espacial, sendo o estudo direcionado a dois canais de comercialização específico, Lojas de Produtos Locais e Comunidades que Sustentam a Agricultura (CSA). Foi utilizado como suporte teórico, no que compete as motivações na aquisição de produtos agroalimentares em cadeias curtas, a teoria das convenções, especificamente as convenções da qualidade, uma vez que ela norteia a forma como o indivíduo toma decisão de compra nesses canais específicos. A coleta de dados foi realizada em lojas de produtos locais de São Paulo/SP e Botucatu/SP, além de CSA’s em diversas regiões do país, utilizando como metodologia uma abordagem quali-quanti. Na fase quantit... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: In the past quality was perceived as meeting standards, today when we speak of quality, we refer to the attendance of several attributes, often subjective to the products or services. Currently, food production is dominated by a production system that has undergone a series of societal questions about loss of nutritional values, environmental problems caused, economic impacts on smallholder, and lack of clear identification of who produces it. Thus, the quality of food, which until then had as synonymous the service to standards, has taken on another meaning linked to social, environmental and location values. In this way, this work identified and analyzed the quality attributes valued by consumers who buy products in short chains of spatial proximity, the study was directed to two specific marketing channels, Local Products Stores and Communities that Support Agriculture (CSA). The theory of conventions, specifically the conventions of quality, was used as a theoretical support, as it relates to motivations in acquisition of agri-food products in short chains, since it guides the way in which the individual makes purchasing decision in these specific channels. Data collection was carried out at local products stores in São Paulo / SP and Botucatu / SP, as well as CSAs in several regions of the country, using a qualitative-quantitative approach as methodology. In quantitative phase, the use of Exploratory Factor Analysis (EFA) and Confirmatory Factor Analysis (CFA) were neces... (Complete abstract click electronic access below)
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Koganti, Naga Babu. "Modeling and Characterization of Circuit Level Transients in Wide Bandgap Devices". University of Toledo / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=toledo153311831687909.
Texto completoZhou, Xigen. "Electrical, Magnetic, Thermal Modeling and Analysis of a 5000A Solid-State Switch Module and Its Application as a DC Circuit Breaker". Diss., Virginia Tech, 2005. http://hdl.handle.net/10919/28900.
Texto completoPh. D.
Alvarez, George Francisco Centre of Health Informatics UNSW. "Interruptive communication patterns in the intensive care unit ward round". Awarded by:University of New South Wales. Centre of Health Informatics, 2006. http://handle.unsw.edu.au/1959.4/23430.
Texto completoToudji, Mustapha. "Développement de méthodes d'analyse des contraintes sur les isolants inter-spires des bobinages des machines électriques". Thesis, Artois, 2017. http://www.theses.fr/2017ARTO0212.
Texto completoThe transition to a higher DC voltage network is the most suitable solution to meet with the steady increase in the need/requirement for power flowing in the networks. Today, the control of embedded electric actuators involves the massive use of electronic converters that impose sudden voltage variations. The latter, when applied to an electrical machine windings, generates high electric field levels between the insulators, exceeding sometimes the partial discharge inception voltage (PDIV). Exceeding this threshold leads to the appearance of partial discharges, which are particularly harmful to the turn-to-turn insulation and are responsible for a very rapid deterioration of the electrical insulation system.This physical phenomenon is the main element of the problem on which these research works are based. In this thesis, a numerical tool was developed, which allows prior to the electrical machine design, to predict the electrical stresses applied to the machine's insulation system. This tool should allow the development of new solutions in the various research axes on the aging problem of electric actuators. It involves the development of an RLC lumped element equivalent circuit whose parameters were computed by means of a finite elements analysis considering both the geometry of turns and its location in the coil. Firstly, this tool is used to analyse the electrical stresses applied to the inter-turns insulation of the windings in order to localize the critical zones in the electrical windings. A method based on a simulation of the distribution of the electric field in the windings as a function of time has been developed. The visualization and analysis of electric field maps over a defined time interval allow to determine and to localize the maximum electrical stresses applied to the turn-to-turn insulation. Secondly, to study the aging of the electrical insulation system and to improve the detection methods, a diagnosis assistance tool is proposed. This tool is based on a calculation of the the resonance frequencies’ variations which are most sensitive to the ΔC indicator tested in the laboratory. In order to refine the possibilities of diagnosis, new correlations have been sought, analysed and highlighted
Boileau, Thierry. "Contribution à la continuité de service des actionneurs synchrones à aimants permanents. Tolérance au défaut de capteur mécanique. Détection de Défauts Electriques". Thesis, Vandoeuvre-les-Nancy, INPL, 2010. http://www.theses.fr/2010INPL068N/document.
Texto completoIn embedded systems, electric actuators tend to replace hydraulic ones for compactness and manoeuvrability reasons. However, these electric actuators should be as reliable as hydraulic ones. For these actuators, adapted power topologies should be chosen in order to operate even if a failure occurs in the electromechanical conversion chain. To ensure the continuity of service in fault case, different kinds of actuator’s failures should be detected in time. Obviously, the detection methods should be adapted to the fault types. In this work, we developed two aspects related to the continuity of service, the first one on the sensorless control of permanent magnet synchronous machines (PMSM), its robustness and its application in mechanical sensor loss case. The second one deals with the detection of inter-turn insulation fault in stator windings of permanent magnets synchronous machines supply by voltage inverter. In a first time a PMSM model with inter-turn fault is developed, this model allows us to propose two detection methods. Both methods are based on the electric unbalance of the machine and are experimentally validated. Finally a third method based on resistance estimation is presented. These three methods are real time methods and no extra sensor is needed for a standard control
Cunha, Carla Maria Santana Duarte Correia da. "Minimização do número de más viragens na recolha de resíduos sólidos urbanos". Master's thesis, Instituto Superior de Economia e Gestão, 2001. http://hdl.handle.net/10400.5/18825.
Texto completoO problema da determinação de percursos a efectuar por veículos afectos à remoção de resíduos sólidos urbanos pode ser visto como um problema de optimização de rotas, com procura nos arcos e restrições adicionais. Usualmente os algoritmos para determinar soluções admissíveis para este tipo de problemas não têm em conta o tipo de viragem que os veículos são obrigados a fazer. Dadas as características dos veículos envolvidos na recolha de resíduos, entende-se por má viragem uma inversão de marcha ou uma viragem à esquerda. Na prática é, em geral, exigida a minimização do número de más viragens, devendo mesmo algumas ser impossibilitadas, quer por se tornarem perigosas, quer por questões de regras de trânsito. Neste trabalho o problema da minimização do número de más viragens é definido e modelizado como um problema de redes. São desenvolvidos métodos para a determinação de soluções admissíveis. Os métodos implementados são testados num conjunto de problemas teste gerados aleatoriamente. Como se mostra, os resultados podem ser considerados bastante bons, dado permitirem obter soluções com um baixo número de más viragens sendo evitadas a quase totalidade das inversões de marcha proibidas. Muito embora a heurística se baseie na expansão da rede nos nodos onde as inversões de marcha não são permitidas, os resultados permitiram concluir que nem todos os nodos têm que ser expandidos para que as respectivas inversões de marcha sejam impossibilitadas.
Finding the optimal set of tours for vehicles dedicated to household refuse collection can be looked at as an are routing problem with additional constraints. Typically, the algorithms used in determining feasible solutions to these problems do not account for the type of turn that the vehicles actually must perform. Given the specifíc characteristics of the vehicles assigned to household refuse collection, a bad-turn translates to a U-turn or to a left-turn. In practical terms it is generally mandatory to minimize the total number of bad-turns, some of which really must be avoided either due to its intrinsic danger or to traffic regulation restrictions. Throughout this thesis the problem of minimizing the number of bad-turns is defmed and modeled as a network problem. Some methods are developed to determine feasible solutions. These methods have been tested over a set of randomly generated problems. It is shown that the overall results are to be considered pretty good since they represent feasible solutions with a very low number of bad-turns, where nearly every forbidden U-turns are avoided.
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Zabihi, Sasan. "Flexible high voltage pulsed power supply for plasma applications". Thesis, Queensland University of Technology, 2011. https://eprints.qut.edu.au/48137/1/Sasan_Zabihi_Sheykhrajeh_Thesis.pdf.
Texto completoTzu-YangLo y 羅子洋. "On-line Inter-turn Short-circuit Fault Detection for PMSM based on Signal Analysis". Thesis, 2019. http://ndltd.ncl.edu.tw/handle/u9c34r.
Texto completoJia-JyunLi y 李家駿. "Inter-turn Short-circuit Fault Detection System of Permanent Magnet Synchronous Motor Using Machine Learning". Thesis, 2019. http://ndltd.ncl.edu.tw/handle/ucx337.
Texto completoΔάλλας, Στέφανος. "Υπολογισμός ηλεκτρομαγνητικών μεγεθών και πρόβλεψη συμπεριφοράς μιας σύγχρονης μηχανής με έκτυπους πόλους σε περιπτώσεις σφαλμάτων με τη χρήση της μεθόδου των πεπερασμένων στοιχείων". Thesis, 2012. http://hdl.handle.net/10889/5429.
Texto completoThis thesis deals with the functional behavior of a salient pole synchronous generator during two kinds of short-circuits. In particular, we studied the case of short circuit in the supply of the excitation winding of the synchronous machine when it is connected to an infinite bus and either the rotor speed was absolutely constant, or a simple PI- Controller maintained the synchronous speed equal to the synchronous. Additionally, the case of an internal fault in the stator winding for the two cases mentioned above was investigated. The electromagnetic torque and the magnetic flux density in each case were calculated and studied, as well as the stator and rotor currents, including the damper cage, and the short-circuit current in the faulty loop of the stator winding. Firstly, it is described in detail the way in which the salient pole synchronous generator was modeled and it is analyzed the method by which the faults are modeled in both stator and rotor and the way these faults were simulated, in the finite element program. Additionally, it is presented the way in how the areas of the model are defined, the equations that were solved through finite element software, in order to extract the results, the definition of the boundary conditions and finally it is described the finite element method, which was applied to this specific model. The case of a short circuit in the supply of the field winding while the stator of the synchronous machine is connected to the grid and the rotor speed is held constant and equal to the synchronous one, is examined. During this fault the magnetic flux, the electromagnetic torque and all the stator and rotor currents are measured in detail. Useful conclusions about the behavior of the machine throughout this kind of short-circuit were derived, all the electromagnetic magnitudes were recorded and an assessment of the generator behavior during this transient phenomenon is made. Similarly, the same type of fault is analyzed, but the speed of the rotor is maintained constant through a speed controller. It is observed that the behavior of the machine and all the electromagnetic magnitudes are quite different compared to the previous case. In this dissertation is examined the behavior of the hydrogenerator in the case of an inter-turn short circuit in the stator winding, while it is connected to the grid with a constant rotor speed. Specifically, it is examined the currents in the rotor and the stator winding for a short circuit between turns that belong to the same or to different phases. The short circuit current is calculated and it is presented the way that it affects quantitative and qualitative the stator phase currents. It is also analyzed the damper currents and it is studied their behavior during the short circuit. The speed controller alters the behavior of the synchronous generator and all the electromagnetic magnitudes of this machine are analytically calculated, resulting significant conclusions on how the faulty loop affects these quantities, while it is set out the role of the participating phases in this short-circuit. Finally, a brief comparison of the way that the number of the shorted turns affects the behavior of the simulated machine in the case of an inter-turn stator fault, while it is connected to the grid with a fixed number of the rotor revolutions. Specifically, it is analyzed the stator and rotor currents and the electromagnetic torque, for the cases that the short-circuited turns belong either to the same or to different phases, but with different number of shorted turns. It is concluded that a key role in determining the electromagnetic magnitudes during this fault has the number of the short-circuited turns and not the number of the phases that are involved in the short circuit.
Cho, Kyoung Min. "Modeling the Capacity of Left-Turn and Through Movement Considering Left-Turn Blockage and Spillback at Signalized Intersection with Short Left-Turn Bay". 2009. http://hdl.handle.net/1969.1/ETD-TAMU-2009-08-2944.
Texto completoLee, Hsiao-wen y 李筱雯. "Effects of Turn-Taking on the Audience in Short Consecutive Interpreting". Thesis, 2008. http://ndltd.ncl.edu.tw/handle/85299050496688057228.
Texto completo輔仁大學
翻譯學研究所
96
This study examines the length-of-turns factor in short consecutive interpreting and attempts to determine if this factor influences users when they evaluate the quality of interpretation, meanwhile investigating whether users of the interpreting service have any preference for the length of turn in a specific context. Motivated by lack of research on short consecutive interpreting and personal experience, the study builds its research framework on three elements: short consecutive interpreting, the length factor and the user’s perspective. An experiment is designed to manipulate the length factor to elicit feedback from subjects. Questionnaires are used to find answers to two questions: whether the length factor affects quality evaluation from the user’s perspective and whether the user demonstrates a significant preference for a certain length. The results of this study suggest that users’ preferences for length of turns in such a short consecutive interpreting context converge toward the medium length to a significant extent. According to the explanations given by the subjects, the convergence occurs mainly because the subjects believe a proper length will bring more complete messages and less fragmentary messages in interpretation and will prevent listeners from forgetting previous interpretation. On quality evaluation, the results indicate that lengths do not lead to any significant difference in terms of overall performance, fidelity, fluency, logic and completeness. Therefore, while the preference for the medium length of turns in the study is a clear inclination, this preference seems not to be a factor taken into account when the audience evaluates the quality as a whole in interpreting, or at least, it is not deemed to be a determining factor.
Chuang, Chuan-Wei y 莊傳偉. "The Study of Selecting Short-Turn Operation Zone for Bus Routes Using Smart Card Data". Thesis, 2018. http://ndltd.ncl.edu.tw/handle/4t7h5m.
Texto completo國立交通大學
運輸與物流管理學系
106
Bus is an important transportation mean to satisfy people’s travel demands. Imbalanced loads are significant characteristics of public bus services. Some segments of routes are more crowd than other segments in some specific time intervals. Relevant researches pointed out that short-turning service can address these imbalanced loads and reduce passengers’ average waiting time. This study proposes a method to suggest short-turning service operation segments and time intervals by considering the differences between supplies and demands of public bus services. The data source is from the electronic payments. This study estimates the demand levels of bus routes and the corresponding short-turn operation zone. The results yielded from the proposed model provide the administration authority the suggested short-turning services, which include the names of route, operation direction and the operation time.
Ngobeni, Hangie Veniel. "The perceptions of adult learners about the adult basic education and training practitioners turn-over at the Witbank Education Circuit". Diss., 2018. http://hdl.handle.net/11602/1233.
Texto completoOliver Tambo Institute of Governance and Policy Studies
Adult basic education and training in South Africa is viewed as an instrument for social, economic and political development. However, over the years, the programme faced challenges relating to recruitment and retention of suitably qualified practitioners, resulting in high staff turn-over. The study focused on the perception of adult learners about the adult basic education and training practitioners turn-over at the Witbank education circuit to gain insight into the magnitude of the problem and recommend ways and strategies to address the identified challenges. The study used a mixed method approach, incorporating elements of both quantitative and qualitative research approach. The research sample comprised adult learners, educators, Adult center managers and adult basic education and training coordinators using purposive sampling technique. Data was collected using semi-structured questionnaires and analyzed using the eight steps of Tesch in Cresswell (2009:186). The results of the study revealed that the participants were to a large extent, aware that ABET practitioners’ turnover is a serious problem at the Witbank education circuit. The study participants revealed that lack of commitment and recognition by government to address ABET practitioner turnover decisively is impacting negatively on learners’ motivation, morale, study progress and their relationship with practitioners. This leads ABET learners to not take the ABET programme seriously, and drop of the programme due to lack of progress whereas most ABET practitioners take ABET as a waiting station for better jobs. A number of strategies can be employed to address the challenge of ABET practitioners’ turnover. Amongst others are the following: the basic working conditions of ABET practitioners should be improved. This will automatically translate into job satisfaction and long tenure, thereby counteracting current levels of high staff turnover. ABET practitioners should also be afforded relevant skills development programmes to ensure continuous professional growth and development.
NRF
Armindo, Valdemar Abril. "Diagnóstico e Análise de Avarias nos Enrolamentos Estatóricos de Um PMSM Hexafásico com Controlo Preditivo". Master's thesis, 2021. http://hdl.handle.net/10316/98107.
Texto completoA presente Dissertação teve como principal objetivo propor quatro métodos de diagnóstico de avarias de curtos-circuitos entre espiras nos enrolamentos estatóricos de motores síncronos de ímanes permanentes (PMSMs) de seis fases, funcionando como motor e gerador, quando estes são alimentados por conversores de frequência com uma estratégia de controlo preditivo de corrente. Estes métodos são aqui desenvolvidos e validados por simulação computacional e experimentalmente, sendo comparados entre si em termos de sensibilidade na deteção das referidas avarias.O Capítulo 1 faz uma descrição no âmbito do desenvolvimento contextual desta Dissertação através de um enquadramento e motivação da temática aqui apresentada bem como dos objetivos que se pretenderam alcançar com a realização desta Dissertação. Na secção final deste capítulo é ainda feita uma breve descrição dos fundamentos sobre PMSMs de seis fases.O Capítulo 2 descreve o estado da arte sobre os métodos de diagnóstico de avarias em PMSMs de seis fases. As descrições neste capítulo incluem ainda o modelo matemático dos PMSMs de seis fases.O Capítulo 3 debruça-se de forma mais detalhada sobre os métodos de diagnóstico propostos para análise dos resultados de simulação e experimentais. O Capítulo 4 apresenta os resultados de simulação obtidos com um modelo de simulação computacional baseado em elementos finitos, capaz de simular o comportamento do PMSM de seis fases controlado com uma estratégia de controlo preditivo de corrente, a fim de avaliar os métodos de diagnóstico analisados. O Capítulo 5 apresenta os resultados experimentais obtidos a diferentes regimes de carga e velocidades de funcionamento do PMSM de seis fases com diferentes números de espiras em curto-circuito nos enrolamentos estatóricos. Este capítulo tem como objetivo validar através de resultados experimentais, os métodos propostos nesta Dissertação.O Capítulo 6 apresenta as principais conclusões do trabalho, propondo ainda um novo método de diagnóstico de curtos-circuitos entre espiras para trabalho futuro.
The main objective of this dissertation was to propose four methods for diagnosing short-circuits failures between turns in stator windings of six-phase permanent magnet synchronous motors (PMSMs), working as motor and generator when they are powered by frequency converters with a predictive current control strategy. These methods are here developed and validated by computer simulation and experimentally, being compared to each other in terms of sensitivity in detecting said failures.Chapter 1 provides a description within the context of the contextual development of this Dissertation through a framework and motivation of the theme presented here as well as the objectives that were intended to be achieved with the realization of this Dissertation. In the final section of this chapter, there is also a brief description of the fundamentals of six-phase PMSMs.Chapter 2 describes the state of the art on troubleshooting methods for six-phase PMSMs. The descriptions in this chapter also include the mathematical model of the six-phase PMSMs.Chapter 3 takes a more detailed look at the diagnostic methods proposed for analyzing simulation and experimental results.Chapter 4 presents the simulation results obtained with a computational simulation model based on finite elements, capable of simulating the behaviour of the six-phase PMSM controlled with a predictive current control strategy, in order to evaluate the analyzed diagnostic methods.Chapter 5 presents the experimental results obtained at different load regimes and operating speeds of the six-phase PMSM with different numbers of short-circuited turns in the stator windings. This chapter aims to validate, through experimental results, the methods proposed in this Dissertation.Chapter 6 presents the main conclusions of the work, also proposing a new method for diagnosing short circuits between turns for future work.
Outro - A minha formação foi financiada pela empresa Sonangol EP.