En chargeant en courant une inductance supraconductrice, on stock de l’énergie magnétique. Ce principe est appelé SMES pour Superconducting Magnetic Energy Storage. Ce type de dispositifs a une densité d’énergie relativement faible mais peut avoir une densité de puissance élevée. Cette thèse s’inscrit dans le cadre du projet BOSSE, qui vise à mettre au point un démonstrateur de SMES dans la gamme du MJ. Ce SMES sera à la fois plus compacte que ses prédécesseurs et battra le record actuel d’énergie spécifique d’un bobinage supraconducteur en atteignant 20 kJ/kg. Cet objectif sera atteint grâce à l’utilisation de supraconducteurs haute température critique de seconde génération, dits conducteurs « REBCO ».Cette thèse aborde de manière générale la problématique du design de SMES et propose des éléments de réflexion et des solutions pour un pré-design rapide du bobinage d’un SMES. Le design du SMES à haute densité d’énergie du projet BOSSE est détaillé.Des éléments modulaires (galettes de ruban REBCO) du SMES ont été fabriqués et testés en champ propre et sous champ magnétique externe. Les méthodes et les résultats de détection de transition des galettes de l’état supraconducteur vers l’état normal sont présentés. Ces détections ont permis de garantir l’intégrité des galettes REBCO lors de transitions, même à très forte densité de courant (980 A/mm2 dans le conducteur nu).Ce travail est soutenu par la DGA (Direction Générale de l’Armement). / Magnetic energy is stored when a superconducting inductance is fed with current. This principle is called SMES (Superconducting Magnetic Energy Storage). This kind of device has a relatively low energy density but can have a high power density. This PhD work has been conducted in the frame of the BOSSE project with the objective to develop a SMES demonstrator in the MJ range. This SMES will be especially compact and will reach a specific energy of 20 kJ/kg of winding, which is 50 % over the current world record for a superconducting coil. This performance is made possible by the use of 2nd generation high critical temperature superconductors, so-called “REBCO” conductors.This work tackles the general problematic of SMES design and proposes elements of reflection and solutions for fast pre-design of a SMES winding. The design of the high specific energy SMES of the BOSSE project is presented in detail.Modular elements (pancakes of REBCO tapes) of the SMES have been manufactured and tested in self-field and under background magnetic field. During these tests, transitions from superconducting state to normal state have been detected. These early detections have prevented the pancakes to be damaged when transitions occurred, even at very high current density (980 A/mm2 in the bare conductor). The measurement method is presented, as well as the results of the tests.The BOSSE project has been funded by the DGA (French Defence Procurement Agency).

Le développement d’avions plus électriques se traduit par une plus grande utilisation d'actionneurs électriques qui remplacent des systèmes hydrauliques et pneumatiques existants ou répondent à de nouveaux besoins. La distribution de l'énergie à bord est basée sur un réseau continu 540V connecté à des convertisseurs électroniques de puissance. Les composants électroniques de puissance à grands gaps (SiC, GaN) améliorent les performances des convertisseurs mais les fronts de tension très raides sont imposés aux bobinages des actionneurs électriques. Chaque front excite un régime transitoire comportant une surtension importante et donc des champs électriques intenses dans l’isolation inter-spires des bobines. Lorsque cette contrainte électrique répétitive dépasse le seuil d'apparition des décharges partielles (PDIV), la durée de vie des couches organiques qui isolent les spires est fortement réduite. L'étude détaillée des décharges partielles (DP) dans l'espace qui sépare les fils émaillés des bobinages permet de situer les zones dans lesquelles les DP se produisent. Elle montre que le thermocollage, avec des surépaisseurs adaptées de thermocolle, permet d'élever le PDIV au-delà des pointes répétitives de tension pour les actionneurs qui fonctionnent dans les parties pressurisées des avions. Des solutions ordonnées de bobinages ont été expérimentées sur des bobines cylindriques imprégnées. Cette analyse montre que l'imprégnation augmente légèrement le PDIV de l'isolation inter-spires dans des proportions qui ne correspondent pas totalement aux caractéristiques intrinsèques du vernis utilisé. Par conséquent, les bobines imprégnées doivent être conçues sur la base des performances de l'isolation primaire du fil émaillé. L’arrangement des spires dans une bobine ordonnée permet de répartir les contraintes et donc de concevoir des bobines qui résistent aux pointes de tension répétitives imposées par l'onduleur aux basses pressions correspondant aux zones non pressurisées d'un avion en vol. Un modèle, basé sur un schéma équivalent HF prenant en considération les deux premières résonances des bobines élémentaires, permet d'analyser la répartition des contraintes entre les bobines connectées en série d'une phase. / The More Electric Aircraft development is reflected by a bigger use of the electrical actuators, which replace the hydraulic or pneumatic system existing or they can also answer to new needs. The energy distribution on board is based on a high voltage continuous bus of 540V connected to electrical power converter. The electric power wide band gap components (SiC, GaN) improve the converters performances but very steep of voltage edge is imposed on the windings of the electric actuators. Each edge excites a transitory regime including an important surge which corresponds to intense electric fields in the inter-turns insulation of coils. When this repetitive electrical constraint exceeds the partial discharges inception voltage (PDIV), the life time of the organic layer between the turns is strongly reduced. The detailed study of the partial discharges (PD) in the area which separate the enamel wire of the windings allows to locate the area where the PD appears. The use of thermo-bonding, with a bonding thickness adapted, allows to raise PDIV beyond the repetitive edge of voltage for the actuators which work in the pressurized parts of the planes. The orderly windings solutions were tested on impregnated cylindrical coils. This analysis shows that the impregnation increases slightly the PDIV from the inter-turns insulation in proportions that do not totally correspond to the intrinsic characteristics of the used varnish. Therefore, the impregnated coils must be conceived on the basis of the primary insulation performance of the enamelled wire. The turn’s arrangement in an orderly coil allows to distribute the constraints and so to conceive the windings which can resist the compulsory repetitive of voltage spikes by the inverter in low pressures corresponding to not pressurized zones in a plane during the flight. A model, based on HF equivalent schema taking in consideration the first two resonances of the elementary coils, allows to analyse the constraints distribution between the coils connected in series of a machine phase.

Thesis. 1978. Ph.D.--Massachusetts Institute of Technology. Dept. of Electrical Engineering and Computer Science. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Vita. / Includes bibliographical references. / Ph.D.

Thesis. 1975. Ph.D.--Massachusetts Institute of Technology. Dept. of Mechanical Engineering. / Vita. / Includes bibliographical references. / Ph.D.

Thesis. 1977. M.S.--Massachusetts Institute of Technology. Dept. of Electrical Engineering and Computer Science. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Includes bibliographic references. / by Craig G. Prohazka. / M.S.

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

M. Tech. Electrical Engineering. / Discusses the placement of windings in the slots of high phase order induction machines (HPOIMs) leads to a stepped-like waveform of stator (rotor) MMFs which exhibit space harmonics as well as the fundamental wave. The interaction of air-gap field components, which have the same pole number but rotate at different speeds, produce the torque ripple whose magnitude depends on the product of the magnitude of the two interacting fields. The frequency of the torque ripples also depends on the difference between the speeds of these two fields. A winding configuration or a combination of different configurations that reduces some air-gap components has the edge in terms of mitigating the ripple torque contents.

No description available.

Industry always searches the least expensive solution for a machine design. Therefore, there is a need for integrating different customer ordered machines within the same frame, while keeping the foundation of the mechanical design constant. Since the winding design in electrical machines is essential for the performance and relatively inexpensive to adapt, it can be used to meet different customer demands. This thesis investigates the foundations of a special winding named fractional conductor winding. An expression for winding factors for certain kinds of these windings is developed. Calculations showed that the selection of the winding distribution has effect on the air gap space harmonics produced by the winding. In some cases, the fifth and seventh space harmonics can be eliminated by the use of fractional conductor windings in combination with short pitching. The construction of a prototype fractional conductor wound induction motor was documented and is presented in this thesis. The air gap flux density in a dual slotted fractional conductor wound induction motor running at no load is studied. Analytical models are compared to results obtained by finite elements and measurements. It was found that analytical results overestimated the peak of the fundamental flux density by 13.5%. The overestimation was caused by the iron reluctance of the main flux path as well as saturation. Leakage was found to be a minor cause of this overestimation. Slot leakage and differential leakage in machines having these windings are studied. The analytical models were evaluated, with mostly good agreements, compared to finite element modeling as well as measurements. / QC 20100427

No description available.