<p>This thesis presents a study of the effects of inter-bar currents on inductionmotor starting performance and stray-load losses. The work is focused on theperformance differences between aluminium and copper casted rotors.A method to predict the stator current when starting direct-on-line isdeveloped. This includes modelling of skin-effect, saturation of the leakageflux paths and additional iron losses. The results are verified by measurements.An analytical model accounting for inter-bar currents is derived, andthe dependency of the harmonic rotor currents on the inter-bar resistivity isinvestigated. It is found that the inter-bar currents can have considerableeffect on motor starting performance and stray-load losses, the amount beingstrongly dependent on the harmonic content of the primary MMF.Based on measurements of inter-bar resistivity, the starting performanceof an aluminium and a copper casted rotor is simulated. The results indicatea higher pull-out torque of the aluminium rotor than for the equivalent copperrotor. This is rather due to an increase of the fundamental starting torque ofthe aluminium rotor, than due to braking torques from the space harmonicsin the copper rotor. The results are verified by measurements. It is foundthat the difference between the pull-out torques is even larger than calculatedfrom the model. Thereby, it can be concluded that the inter-bar currents havea considerable effect on motor starting performance.At rated speed the braking torques are larger in the aluminium rotor thanin the copper rotor. This is seen as increased harmonic joule losses in the rotorcage. Simulations have shown, that these losses can be as large as 1% ofthe output power for the studied machine.</p> / QC20100617

The nature of the relationship between the Pitted Ware Culture and the Boat Axe Culture has dominated Swedish Middle Neolithic research, since the question was raised a century ago. Basically, the debate is concerned with whether or not the two material cultures express two different ethnical groups. Proponents for the currently established perspective stress that the cultures represent two distinct ethnic groups. A large amount of research has focused on identifying differences between the two cultures in the archaeological record. This study will test an alternative approach to the archaeology of the Middle Neolithic. Rather than presuming an antithetical relationship between the two cultures attention will be given to investigating the relationship between the Pitted Ware Culture and the Boat Axe Culture. This will be done by a landscape centered approach. In the first case I will test the conventional opinion expressing that the two cultures are spatially separated to the coast and the inland. In addition, the analysis seeks to understand how different activities were located in relation to various landscape phenomena. In the second case study, phenomenology and current landscape theory combined with a viewshed GIS-analysis will form the basis for a discussion regarding the localisation and function of the Pitted Ware sites. In the third case I will discuss connective features of the Middle Neolithic landscapes in the Lake Hjälmaren area. Focus will be given to the long-term processes and the reproduction of the cultural landscapes over time. Based on the results, I will propose that the Middle Neolithic archaeological record, rather than being the result of two ethnic groups, express a dynamic and active society that manifests itself through a variety of different places, which were maintained for specific purposes.

This thesis presents a study of inter-bar current effects on induction motors with die-cast aluminium and die-cast copper rotors. The parasitic effects introduced by these currents are analyzed and possible solutions to these problems are presented. This is realized by developing analytical tools for the simulation of inter-bar current effects. The methods used are verified by measurements on prototype machines. It is shown that the inter-bar currents can have a considerable effect on the motor starting performance, which can result in a reduced pull-out torque. At rated operation, this is seen as increased harmonic rotor currents, having a negative effect on the motor performance. Results from calorimetric measurements show, that the efficiency gained when substituting a skewed die-cast aluminium rotor with a skewed die-cast copper rotor, is less than the theoretical expectation. It is shown that this is a result of a reduced power factor for the copper rotor. High inter-bar currents are believed to be the origin of this effect, increasing the harmonic content in the rotor magnetomotive force. This would be seen as an increased rotor leakage reactance. Results from locked-rotor tests, and simulations using measured values of inter-bar resistance, support this theory. It is shown, that these negative effects are suppressed to a negligible level by the use of an unskewed rotor, but to the expense of a large synchronous torque at a low speed. By using a modulated rotor concept, having an asymmetrical rotor slot distribution, an unskewed rotor is designed to reduce this parasitic torque. Measurements on a prototype machine show that the modulated rotor suppresses both the inter-bar currents and the synchronous torque, resulting in an improved starting performance, without any significant change of the motor efficiency. The presented results strengthen the potential of the modulated rotor concept, introducing new possibilities for the reduction of negative effects appearing in induction machines. / <p>QC 20130320</p>

Les principaux critères de comparaison des convertisseurs sont le rendement, la masse, le volume, le coût et la fiabilité. Le contexte environnemental et économique et le développement des applications nomades ouvrent à l’électronique de puissance un domaine d’application de plus en plus vaste. Mais pour imposer cette technologie, il faut sans cesse améliorer ces performances et les compromis entre celles qui sont antagonistes (augmentation du rendement et diminution de la masse par exemple…) ce qui amène naturellement à la problématique de conception et d’optimisation. Le cas spécifique de l’aéronautique n’échappe pas à la règle et les contraintes y semblent encore plus fortes. La réduction de la masse, du volume et l’augmentation du rendement et de la fiabilité sont parmi les défis principaux actuels, et la transition de systèmes hydrauliques ou pneumatique vers des systèmes électriques laisse espérer à une amélioration des performances globales de l’avion. Les architectures des convertisseurs sont un moyen efficace d’améliorer les convertisseurs parce qu’ils permettent de réduire les contraintes au sein des convertisseurs tout en améliorant les formes d’onde en entrée et/ou en sortie. Parallèlement, les composants classiques en silicium ont bénéficié de larges avancés au cours de ces dernières décennies et approchent de leurs limites théoriques. Pour espérer une amélioration, des technologies en rupture sont désormais nécessaires. Au cours de ces dernières années, les technologies de semi-conducteurs dit « à grand gap », essentiellement à base de Nitrure de Gallium ou de Carbure de Silicium (resp. GaN et SiC) se sont considérablement amélioré et sont d’ores et déjà plus performant que les composants Si dans de nombreux cas. Les semi-conducteurs étant généralement plus performants lorsqu’ils ont une tenue en tension plus faible, on envisage ici de cumuler plusieurs avantages en envisageant la mise en série de composants GaN basse-tension pour améliorer l’intégration des convertisseurs de puissance. Dans un premier temps, un convertisseur multi-niveaux élémentaire de type Flying Capacitor (FlyCap) est mis en oeuvre. Des condensateurs de puissance intégrés sont utilisés, ce qui pourrait permettre de réduire l’empreinte de ces composants et de proposer une dissipation thermique commune par le dessus des composants. L’utilisation de composant au temps de commutation réduit est critique pour la fiabilité des convertisseurs. Une étude de l’influence des paramètres physique du circuit électrique sur les inductances parasites de la maille de puissance et de commande est menée permettant de mettre en évidence des règles de conception dans le but d’améliorer la fiabilité des convertisseurs. Dans un second temps, l’équilibrage dynamique de la topologie FlyCap qui est critique pour les formes d’onde et la sureté de fonctionnement est étudié. La prise en compte des pertes dans les semi-conducteurs permet d’améliorer l’estimation de la dynamique d’équilibrage. Une base de réflexion sur le dimensionnement d’un équilibreur passif est également proposée pour optimiser sa dynamique et les pertes associées. Un prototype expérimental à 5 cellules de commutation est présenté permettant d’atteindre une tension d’entrée de 270 V avec des composants 100V. / Performance, weight, volume, cost and reliability are key criteria to compare converters. Environment and economical context and the development of mobile applications lead electronics to have a wider field of application. Improving performances and tradeoff between conflicting characteristics (high efficiency and reduced weight for example) is thus constantly needed to impose this technology, which calls for design and optimization methods and tools. The specific case of aeronautics is no exception and there is in this field a high demand. Mass and volume reduction, efficiency and reliability improvement is one of the most important challenges, and the change from hydraulic and pneumatic systems to electric systems is expected to allow a global improvement of aircraft performances. Converter’s topology is a good candidate to improve and reduce the size of converters because it can reduce stress while improving the input and/or output waveforms. Meanwhile, conventional silicon components have taken advantage of wide advances in recent decades and are now close to their theoretical limits. To hope for a significant improvement, breaking technologies are now needed. In recent years, GaN and SiC Wide Band Gap semiconductors have seen significant development and are already often better than Si power devices. Lowvoltage semiconductors are generally better than higher voltage ones. Thus, we consider here cumulating advantages with a serial arrangement of low voltage GaN semi-conductors to improve power converter’s integration. First, a basic multilevel Flying Capacitor GaN-based converter is implemented. The integration of power capacitors is proposed to evaluate this technology, which could reduce the footprint of these components and could allow a common heatsink dissipation through the top of the components. Very fast turn-on and turn-off of GaN devices is critical for safe operation due to parasitic inductances. A study of physical parameters of the electrical circuit on parasitic inductances of power and control loop is conducted to lay down design rules in order to improve the reliability of converters. Secondly, dynamic balancing of Flying Capacitor which is critical for the waveforms and reliability is studied. Semi-conductor’s losses are considered to improve the estimation of dynamic balancing. A method for the design of a passive balancer is also proposed to optimize the balancing and associated losses. An experimental prototype with 5 switching cells is presented to achieve an input voltage of 270 V with 100 V rated voltage devices.

Submitted by Luciana Ferreira (lucgeral@gmail.com) on 2014-11-27T12:38:45Z No. of bitstreams: 3 Tese - Rosana Maria Ribeiro Borges - 2013 - (1).pdf: 18910292 bytes, checksum: 63e589af2728a1829cb9e0b9ef5ce125 (MD5) Tese - Rosana Maria Ribeiro Borges - 2013 - (2).pdf: 12347689 bytes, checksum: f814045ac80b3cbd07e9fb77c861382e (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2014-11-27T14:21:09Z (GMT) No. of bitstreams: 3 Tese - Rosana Maria Ribeiro Borges - 2013 - (1).pdf: 18910292 bytes, checksum: 63e589af2728a1829cb9e0b9ef5ce125 (MD5) Tese - Rosana Maria Ribeiro Borges - 2013 - (2).pdf: 12347689 bytes, checksum: f814045ac80b3cbd07e9fb77c861382e (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) / Made available in DSpace on 2014-11-27T14:21:09Z (GMT). No. of bitstreams: 3 Tese - Rosana Maria Ribeiro Borges - 2013 - (1).pdf: 18910292 bytes, checksum: 63e589af2728a1829cb9e0b9ef5ce125 (MD5) Tese - Rosana Maria Ribeiro Borges - 2013 - (2).pdf: 12347689 bytes, checksum: f814045ac80b3cbd07e9fb77c861382e (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) Previous issue date: 2013-02-14 / This Thesis aims to analyze the relationship of journalistic discourses with the movements of territorialization in the Cerrado. One of the main assumptions is the understanding that ownership and capture of the territories includes their meanings. Then, in the contemporary world, the territorialization relates also to what is reported by the vehicles of journalism and communication, which select, edit and broadcast news. These institutions are not loose in the world: are part of the networks that make up part of the dispute, and most of them follows the logic of power and capital. In the condition of a territory in a dispute material and symbolic, the Cerrado is wrapped by problematic that transposing the degeneration of the biome and ways of life when interconnect up to what it is meaning. This fact implies on the perception that the processes of territorialization in Cerrado permeate there senses, thare are made and disseminated through discourses and images nothing neutral, that integrate many networks, such as economic, ideological, political, power, media, journalism and communication. This fact implies on the perception that the processes of territorialization in Cerrado permeates the meaning, that are made and disseminated through discourses and images nothing neutral, that integrate many networks, such as economic, ideological, political, power, media, journalism and communication. By appropriating and signify the Cerrado, communication vehicles interfere in its territorialization. The main problem of the Thesis relate to the contemporary dramas of the territory of the Cerrado, involving multiple dimensions of power that range from badges historically built on unknown and contempt, also the recent mythologised processes which strengthen the production of a stray thought, based on hegemonies concentrators. The research had the newspaper O Popular as the main clipping, but also analyzed the discourses about the Cerrado present in the magazine A Informação Goyana (1917 – 1935) and the newspaper O Estado de São Paulo, among other periodicals printed less recurring the whole of analysis. The dialectical and historical materialism was used as a guide for analyzing and processing of the information. The research, which was qualitative approach, used the following research methods: bibliographical research, desk research, content analysis and discourse analysis. The plurality of methods has been established from the object itself and its problematization; since it was intended to identify the journalistic discourses about the Cerrado, and especially to see how the discourses were meant and what relations with the movements of territorialization established. The findings point to a new dimension of globalized Cerrado – wrapped in disputes, intrigues and dramas; immersed in networks of communication and journalism possessed of rationalities and systems of signs which, when spread, generates stray thought: at the same time that promote a compliment to the economism and developmentalism, denounce the degradation. This contradiction, which is treated even by journalistic vehicles, confuses the meanings of the Cerrado and has no contributions to the synthesis necessary for the formation of less aggressive movements of appropriation and capture the territory of the Cerrado. / A presente Tese teve como objetivo analisar a relação dos discursos jornalísticos com os movimentos de territorialização no Cerrado. Um dos principais pressupostos está na compreensão de que a apropriação e a captura dos territórios envolvem seus significados. Portanto, no mundo contemporâneo, a territorialização relaciona-se, também, ao que é noticiado pelos veículos de jornalismo e de comunicação, que selecionam, editam e difundem notícias. Essas instituições não estão soltas no mundo: compõem redes que fazem parte da disputa; sendo que a maioria delas acompanha as lógicas do poder e do capital. Na condição de um território em disputa material e simbólica, o Cerrado está envolto em situações que transpõem a degeneração do Bioma e dos modos de vida, ao se interligarem ao que dele é significado. Isso implica na percepção de que os processos de territorialização no Cerrado perpassam por seus sentidos, que são produzidos e disseminados por meio de discursos e imagens nada neutros, que integram diversas redes, tais como as econômicas, ideológicas, políticas, de poder, midiáticas, jornalísticas e comunicacionais. Ao apropriarem o Cerrado e o significarem, os veículos de comunicação interferem na sua territorialização. As principais problemáticas da Tese relacionam-se aos os dramas contemporâneos do território cerradense, envolto em múltiplas dimensões de poder que englobam desde insígnias historicamente edificadas no desprezo e desconhecimento, aos recentes processos mitificadores que fortalecem a produção de um pensamento disperso, alicerçado em hegemonias concentradoras. A pesquisa teve o Jornal O Popular como principal recorte, mas, também, analisou os discursos sobre o Cerrado presentes na Revista A Informação Goyana (1917- 1935) e no Jornal O Estado de São Paulo, entre outros periódicos impressos menos recorrentes no conjunto da análise. O materialismo histórico e dialético foi adotado como guia de análise e tratamento dos dados. A pesquisa, de abordagem qualitativa, utilizou a pesquisa bibliográfica, pesquisa documental, análise de conteúdo e análise de discurso como métodos de investigação, análise e sistematização dos dados. A pluralidade de métodos foi estabelecida a partir do próprio objeto e das suas problematizações, uma vez que se pretendia identificar os discursos jornalísticos sobre o Cerrado, e, sobretudo, perceber como eles eram significados e quais relações com os movimentos de territorialização estabeleciam. As conclusões apontam uma nova dimensão do Cerrado globalizado – envolto em disputas, tramas e dramas; imerso em redes de jornalismo e de comunicação possuidoras de racionalidades e sistemas de signos que, quando disseminados, geram pensamento disperso: ao mesmo tempo em que promovem um elogio ao desenvolvimentismo e ao economicismo, denunciam a degradação. Tal contradição, que sequer é tratada pelos veículos jornalísticos, mitifica e confunde os significados do Cerrado e não contribui com a síntese necessária para a constituição de movimentos menos agressivos de apropriação e captura do território cerradense.

This thesis presents a study of the effects of inter-bar currents on inductionmotor starting performance and stray-load losses. The work is focused on theperformance differences between aluminium and copper casted rotors.A method to predict the stator current when starting direct-on-line isdeveloped. This includes modelling of skin-effect, saturation of the leakageflux paths and additional iron losses. The results are verified by measurements.An analytical model accounting for inter-bar currents is derived, andthe dependency of the harmonic rotor currents on the inter-bar resistivity isinvestigated. It is found that the inter-bar currents can have considerableeffect on motor starting performance and stray-load losses, the amount beingstrongly dependent on the harmonic content of the primary MMF.Based on measurements of inter-bar resistivity, the starting performanceof an aluminium and a copper casted rotor is simulated. The results indicatea higher pull-out torque of the aluminium rotor than for the equivalent copperrotor. This is rather due to an increase of the fundamental starting torque ofthe aluminium rotor, than due to braking torques from the space harmonicsin the copper rotor. The results are verified by measurements. It is foundthat the difference between the pull-out torques is even larger than calculatedfrom the model. Thereby, it can be concluded that the inter-bar currents havea considerable effect on motor starting performance.At rated speed the braking torques are larger in the aluminium rotor thanin the copper rotor. This is seen as increased harmonic joule losses in the rotorcage. Simulations have shown, that these losses can be as large as 1% ofthe output power for the studied machine. / QC20100617

The trend of electrification in transportation applications has led to the fast development of high-power-density power electronics converters. High-switching-frequency and high-temperature operations are the two key factors towards this target. Both requirements, however, are challenging the fundamental limit of silicon (Si) based devices. The emerging wide-bandgap, silicon carbide (SiC) power devices have become the promising solution to meet these requirements. With these advanced devices, the technology barrier has now moved to the compatible integration technology that can make the best of device capabilities in high-power-density converters. Many challenges are present, and some of the most important issues are explored in this dissertation. First of all, the high-temperature performances of the commercial SiC MOSFET are evaluated extensively up to 200 degree C. The static and switching characterizations show that the device has superior electrical performances under elevated temperatures. Meanwhile, the gate oxide stability of the device - a known issue to SiC MOSFETs in general - is also evaluated through both high-temperature gate biasing and gate switching tests. Device degradations are observed from these tests, and a design trade-off between the performance and reliability of the SiC MOSFET is concluded. To understand the interactions between devices and circuit parasitics, an experimental parametric study is performed to investigate the influences of stray inductances on the MOSFETs switching waveforms. A small-signal model is then developed to explain the parasitic ringing in the frequency domain. From this angle, the ringing mechanism can be understood more easily and deeply. With the use of this model, the effects of DC decoupling capacitors in suppressing the ringing can be further explained in a more straightforward way than the traditional time-domain analysis. A rule of thumb regarding the capacitance selection is also derived. A Power Electronics Building Block (PEBB) module is then developed with discrete SiC MOSFETs. Integrating the power stage together with the peripheral functions such as gate drive and protection, the PEBB concept allows the converter to be built quickly and reliably by simply connecting several PEBB modules. The high-speed gate drive and power stage layout designs are presented to enable fast and safe switching of the SiC MOSFET. Based on the PEBB platform, the state-of-the-art Si and SiC power MOSFETs are also compared in the device characteristics, temperature influences, and loss distributions in a high-frequency converter, so that special design considerations can be concluded for the SiC MOSFET. Towards high-temperature, high-frequency and high-power operations, integrated wire-bond phase-leg modules are also developed with SiC MOSFET bare dice. High-temperature packaging materials are carefully selected based on an extensive literature survey. The design considerations of improved substrate layout, laminated bus bars, and embedded decoupling capacitors are all discussed in detail, and are verified through a modeling and simulation approach in the design stage. The 200 degree C, 100 kHz continuous operation is demonstrated on the fabricated module. Through the comparison with a commercial SiC phase-leg module designed in the traditional way, it is also shown that the design considerations proposed in this work allow the SiC devices in the wire-bond structure to be switched twice as fast with only one-third of the parasitic ringing. To further push the performance of SiC power modules, a novel hybrid packaging technology is developed which combines the small parasitics and footprint of a planar module with the easy fabrication of a wire-bond module. The original concept is demonstrated on a high-temperature rectifier module with SiC JFET. A modified structure is then proposed to further improve design flexibility and simplify module fabrication. The SiC MOSFET phase-leg module built in this structure successfully reaches the switching speed limit of the device almost without any parasitic ringing. Finally, a new switching loop snubber circuit is proposed to damp the parasitic ringing through magnetic coupling without affecting either conduction or switching losses of the device. The concept is analyzed theoretically and verified experimentally. The initial integration of such a circuit into the power module is presented, and possible improvements are proposed. / Ph. D.

The Society for the Prevention of Cruelty to Animals of Texas in Dallas, Texas offers an array of services and programs to residents in southern Dallas and other areas. However, interest in the state of access to veterinary care has been questioned for southern Dallas residents. In an area that faces certain compounding stressors, such as food deserts and transportation difficulties, a lack of access to veterinary care for pet owners is considered an additional possible stressor. Pet owners in southern Dallas, along with the SPCA of Texas, contemplate how to best provide medical care for local pets. In this body of work, I describe community access to veterinary services in southern Dallas. I provide a resident-centered explanation based on in-depth interviews with locals that discuss the current state of access to veterinary services while simultaneously analyzing the links between access to veterinary care, the area of southern Dallas itself, and ongoing issues with roaming and stray dogs.

The presence of roman coins outside of the Roman Empire during the Iron Age is a curiousthing. One would assume they represent a giant trade confederation of sorts, and one would notbe completely wrong in assuming so. The trade aspect of the Roman Empire to the north is stillsomething unknown. But this essays focus lies instead with how the coins were used in specificplaces in Scandinavia. This essay focuses on two central places, Gudme in Denmark, andUppåkra in Sweden, while also looking at stray coins in the northern part of Sweden todetermine if there is a correlation between a central place and stray finds out in the wilderness. The analysis of this essay showed a similar yet different use of the roman coins at the twocentral places. In Gudme the norm was to use the coins, as they were, in the metal workshops,or use them as clippings for using a smaller amount of metal in the rework of new items. InUppåkra the norm was instead to melt all coins down to metal bars for an easier storage and useof specific wights and metal in making new items. The correlation between the stray coins anda central place is that hunters or tradesmen travelled through the country and dropped coins.The analysis showed that the travellers where hunting and trading fur that were most likely soldin a central place like Uppåkra and then brought back to settlement in the north / Närvaron av romerska mynt utanför romarriket under järnåldern är en underlig sak. Antagandetsom har gjorts är att de representerade ett handels förbund av ett slag, och en har inte helt fel iatt anta så. Handelsaspekten av romarriket i norr är fortfarande okänt. Fokuset för denna uppsatsligger i stället hur de romerska mynten användes vid specifika platser i Skandinavien.Uppsatsen fokuserar på två centralplatser, Gudme i Danmark och Uppåkra i Sverige, detkommer även kolls på ströfynd i norra delen av Sverige för att ta reda på om en korrelationmellan centralplats och ströfynden i utmarken. Analysen av Uppsatsen visade på en liknande användning av mynten men ändå en olikhetvid de två centralplatserna. I Gudme var normen att använda mynten som de var imetallverkstäderna, eller använda dem som klippningar för att använda en mindre mängd metalli tillverkningen av nya föremål. I Uppåkra smältes mynten i stället ner till metalltackor förenklare förvaring samt att kunna använda en specifik metall eller mängd för att tillverka nyaföremål. Korrelationen mellan utmarksfynden och en centralplats var att jägare ellerhandelsmän reste genom landet och tappade mynt. Analysen visade att de jagade efter päls föratt sälja på centralplatser och fick romerska mynt som betalning och tog mynten till derasbosättningar i norra Sverige.

Les moteurs électriques sont responsables de 67% de la consommation d’électricité dans l’industrie. Remplacer les moteurs installés par des entrainements plus efficients requiert de statuer sur leur adéquation avec les charges qu’ils entrainent. Une contrainte forte est de les analyser « on-line » et sans mesures intrusives ni consignations des installations.Cette thèse répond à un triple objectif. Premièrement, un dispositif de diagnostic « non-invasif » facilement intégrable en milieu industriel a été développé avec quatre méthodes d’évaluation du niveau de charge des moteurs asynchrones directement connectés au réseau. Deux de ces méthodes, existantes et basées sur la mesure du courant et du flux magnétique de dispersion, font l’objet d’améliorations significatives qui les portent à un niveau TRL7. Les deux autres méthodes exploitent la mesure seule du flux de dispersion. Leur applicabilité est vérifiée pour une alimentation par un système de tensions, équilibré ou non, avec des variations permanentes ou aléatoires. Une étude plus exploratoire montre que l’estimation non-invasive du courant absorbé par les machines asynchrones alimentées par convertisseurs électroniques est possible par exploitation du flux rayonné. Deuxièmement, le dispositif de diagnostic énergétique et des algorithmes de recherche de motorisation adaptée à un cycle de fonctionnement défini ont été appliqués à des exemples concrets d’optimisation énergétique sur un site industriel très énergivore, une aluminerie. Troisièmement, cette étude propose une réflexion sur la gestion d’un parc moteurs et, notamment, sur l'analyse des performances des moteurs neufs comparés à ceux ayant subi un rebobinage. / In the industry, electrical motors are responsible for 67% of electricity consumption. Replacing installed motors by more efficient ones requires the knowledge of their suitability with the loads that they drive. Analyzing the load variations without intrusive measurements or installations consignments is a strong constraint.That is why this thesis has a threefold purpose. Firstly, a “noninvasive” diagnostic device has been developed with four methods for evaluating the load of grid-connected induction motors. Two of these methods, based on the measurement of the current and the magnetic stray flux, have been significantly improved up to TRL7. The two other methods exploit only the measurement of the stray flux. Their applicability is checked for balanced and unbalanced supply voltage systems with permanent or random variations. A more exploratory study shows that the noninvasive estimation of the current for inverter-fed induction machines is possible using the radiated external flux. Secondly, the energy diagnosis device and search algorithms adapted to an operating cycle motorization have been applied to practical examples of energy optimization in an electro-intensive industrial plant, an aluminum smelter. Thirdly, a reflection on the management of a motor fleet is proposed, in particular, on the performance analysis between new motors and rewounded ones.