For medium and high-voltage drive applications, multilevel inverters are very popular. It is due to their superior performance compared to 2-level inverters such as reduced harmonic content in the output voltage and current, lower common mode voltage and dv=dt, and lesser voltage stress on power switches. The popular circuit topologies for multilevel inverters are neutral point clamped, cascaded H-bridge and flying capacitor based circuits. There exist different combinations of these basic topologies to realize multilevel inverters with modularity, better fault tolerance, and reliability. Due to these advantages, multilevel converters are getting good acceptance from the industry, and researchers all over the world are continuously trying to improve the performance of these converters. To meet such demands, three multilevel inverter topologies are proposed in this thesis. These topologies can be used for high-power induction motor drives, and the concepts presented are also applicable for synchronous motor drives, grid-connected inverters, etc. To get nearly sinusoidal phase current waveforms, the switching frequency of the conventional inverter has to be increased. It will lead to higher switching losses and electromagnetic interference. The problem with lower switching frequency is the intro- duction of low order harmonics in phase currents and undesirable torque ripple in the motor. The 5th and 7th harmonics are dominant for hexagonal voltage space-vector based low frequency switching, and it is possible to eliminate these harmonics by dodecagonal switching. Further improvement in the waveform quality is possible by octadecagonal voltage space-vectors. In this case, the complete elimination of 11th and 13th harmonic is possible for the entire modulation range. The concepts of dodecagonal and octadecagonal voltage space-vectors are used in the proposed inverter topologies. The first topology proposed in this thesis consists of cascaded connection of two H-bridge cells. The two cells are fed from unequal DC voltage sources having a ratio of 1 : 0:366, and this inverter can produce six concentric dodecagonal voltage space- vectors. This ratio of voltages can be obtained easily from a combination of star-delta transformers, since 1 : 0:366 = ( p 3 + 1) : 1. The cascaded connection of two H-bridge cells can generate nine asymmetric pole voltage levels, and the combined three-phase inverter can produce 729 voltage space-vectors (9 9 9). From this large number of combinations, only certain voltage space-vectors are selected, which forms dodecagonal pattern. In the case of conventional multilevel inverters, the voltage space-vector diagram consists of equilateral triangles of equal size, but for the proposed inverter, the triangular regions are isosceles and are having different sizes. By properly placing the voltage space-vectors in a sampling period, it is possible to achieve lower switching frequency for the individual cells, with substantial improvement in the harmonic spectrum of the output voltage. During the experimental veri cation, the motor is operated at di erent speeds using open loop v=f control method. The samples taken are always synchronised with the start of the sector to get synchronised PWM. The number of samples per sector is decreased with increase in the fundamental frequency to limit the switching frequency. Even though many topologies are available in literature, the most preferred topology for drives application such as traction drives is the 3-level NPC structure. This implies that the industry is still looking for viable alternatives to construct multilevel inverter topologies based on available power circuits. The second work focuses on the development of a multilevel inverter for variable speed medium-voltage drive application with dodecagonal voltage space-vectors, using lesser number of switches and power sources compared to earlier implementations. It can generate three concentric 12-sided polygonal voltage space-vectors and it is based on commonly available 2-level and 3-level inverters. A simple PWM timing computation method based on the hexagonal space-vector PWM is developed. The sampled values of the three-phase reference voltages are initially converted to the timings of a two-level inverter. These timings are mapped to the dodecagonal timings using a change of basis transformation. The voltage space- vector diagram of the proposed drive consists of sixty isosceles triangular regions, and the dodecagonal timings calculated are converted to the timings of the inner triangles. A searching algorithm is used to identify the triangular region in which the reference vector is located. A front-end recti er that may be easily implemented using standard star-delta transformers is also developed, to provide near-unity power factor. To test the performance of the inverter drive, an open-loop v=f control is used on a three-phase induction motor under no-load condition. The harmonic spectra of the phase voltages were computed in order to analyse the harmonic distortion of the waveforms. The carrier frequency was kept around 1.2 KHz for the entire range of operation. If the switching frequency is decreased, the conventional hexagonal space-vector based switching introduce signifi cant 5th, 7th, 11th and 13th harmonics in the phase currents. Out of these dominant harmonics, the 5th and 7th harmonics can be completely suppressed using dodecagonal voltage space-vector based switching as observed in the first and second work. It is also possible to remove the 11th and the 13th harmonics by using voltage space-vectors with 18 sides. The last topology is based on multilevel octadecagonal (18-sided polygon) voltage space-vectors, and it has better harmonic performance than the previously mentioned topologies. Here, a multilevel inverter system capable of producing three octadecagonal voltage space-vectors is proposed for the fi rst time, along with a simple timing calculation method. The conventional three-level inverters are only required to construct the proposed drive. Four asymmetric power supply voltages with 0:3054Vdc, 0:3473Vdc, 0:2266Vdc and 0:1207Vdc are required for the operation of the drive, and it is the main drawback of the circuit. Generally front-end isolation transformer is essential for high-power drives and these asymmetric voltages can be easily obtained from the multiple windings of the isolation transformer. The total harmonic distortion of the phase current is improved due to the 18-sided voltage space-vector switching. The ratio of the radius of the largest polygon and its inscribing circle is cos10 = 0:985. This ratio in the case of hexagonal voltage space-vector modulation is cos30 = 0:866, which means that the range of the linear modulation for the proposed scheme is signifi cantly higher. The drive is designed for open-end winding induction motors and it has better fault tolerance. It any of the inverter fails, it can be easily bypassed and the drive will be still functional with reduced speed. Open loop v=f control and rotor flux oriented vector control schemes were used during the experimental verifi cation. TMS320F2812 DSP platform was used to execute the control code for the proposed drive schemes. For the entire range of operation, the carrier was synchronized with the fundamental. For the synchronization, the sampling period is varied dynamically so that the number of samples in a triangular region is fi xed, keeping the switching frequency around 1.2 KHz. The average execution time for the v=f code was found to be 20 S, where as for vector control it took nearly 100 S. The PWM terminals and I/O lines of the DSP is used to output the timings and the triangle number respectively. To convert the triangle number and the timings to IGBT gate drive logic, an FPGA (XC3S200) was used. A constant dead-time of 1.5 S is also implemented inside the FPGA. Opto-isolated gate drivers with desaturation protection (M57962L) were used to drive the IGBTs. Hall-effect sensors were used to measure the phase currents and DC bus voltages. An incremental shaft position encoder with 2500 pulse per revolution is also connected to the motor shaft, to measure the angular velocity. 1200 V, 75 A IGBT half-bridge module is used to realize the switches. The concepts were initially simulated and experimentally verifi ed using laboratory prototypes at low power. While these concepts maybe easily extended to higher power levels by using suitably rated devices, the control techniques presented shall still remain applicable.

Experimental research on high-power converters, particularly in an academic environment, faces severe infrastructural constraints. Usually, power source and loads of required ratings are not available. Further, more importantly, the energy consumption is huge. One possibility is to establish an experimental research platform, comprising of a network of high-power converters, through which power is circulated and which draws only the losses from the mains. This work deals with the establishment of a circulating power test set-up, comprising of two line-side PWM converters, inclusive of control and modulation methods for the two converters. Two types of circulating power test setups are developed. In the first setup, the converters are connected in parallel, on ac as well as dc sides, such that real and/or reactive power is circulated between them. In the second test setup, the dc buses of the converters are separated; hence, only reactive power circulation is possible. These setups are used to conduct heat-run tests with low energy expenditure on the PWM converters at various operating conditions up to power levels of 150 kVA. Further, these are used to validate analytically-evaluated thermal characteristics of high-power PWM converters. A safe thermal limit is derived for such converters in terms of apparent power (kVA) handled, power factor and switching frequency. The effects of voltage sag and of unequal current sharing between parallel IGBT modules on the safe thermal limit are studied. While the power drawn by the circulating-power setup from the grid is much lower than the ratings of the individual converters, the harmonic injection into the mains by the setup could be significant since the harmonics drawn by both converters tend to add up. This thesis investigates carrier interleaving to improve the waveform quality of grid current, drawn by the circulating-power test setup. The study of carrier interleaving is quite general and covers various applications of parallel-connected converters such as unity power factor rectification, static reactive power compensation and grid-connected renewable energy systems. In literature, carrier interleaving has been employed mainly for unity power factor rectifiers, sharing a common dc load equally. In such case, the fundamental components of the terminal voltages of the parallel converters are equal. However, when the power sharing between the two converters is unequal, or when power is circulated between the two converters, the terminal voltages of the two converters are not equal. A method to estimate rms grid current ripple, drawn by parallel-connected converters with equal and/or unequal terminal voltages, in a synchronous reference frame is presented. Further, the influence of carrier interleaving on the rms grid current ripple is studied. The optimum interleaving angle, which minimizes the rms grid current ripple under various applications, is investigated. This angle is found to be a function of modulation index of the converters in the equal terminal voltages case. In the unequal terminal voltages case, the optimum interleaving angle is shown to be a function of the average modulation index of the two parallel converters. The effect of carrier interleaving is experimentally studied on the reactive power circulation setup at different values of kVA and different dc bus voltages. The grid current ripple is measured for different values of interleaving angle. It is found experimentally that the optimum interleaving angle reduces the rms grid current ripple by between 37% and 48%, as compared without interleaving, at various operating conditions. Further, the reactive power circulation test set-up is used to evaluate and compare power conversion losses corresponding to different PWM techniques such as conventional space-vector PWM (CSVPWM), bus-clamping PWM (BCPWM) and advanced bus-clamping PWM methods for static reactive power compensator (STATCOM) application at high power levels. It is demonstrated theoretically as well as experimentally that an advanced bus-clamping PWM method, termed minimum switching loss PWM (MSLPWM), leads to significantly lower power conversion loss than CSVPWM and BCPWM techniques at a given average switching frequency.

Ideal prostheses are defined as artificial limbs that would permit physically impaired individuals freedom of movement and independence rather than a life of disability and dependence. Current lower limb prostheses range from a single mechanical revolute joint to advanced microprocessor controlled mechanisms. Despite the advancement in technology and medicine, current lower limb prostheses are still lacking an actuation element, which prohibits patients from regaining their original mobility and improving their quality of life. This thesis aims to design and test a Pneumatic Artificial Muscle that would actuate lower limb prostheses. This would offer patients the ability to ascend and descend stairs as well as standing up from a sitting position. A comprehensive study of knee biomechanics is first accomplished to characterize the actuation requirement, and subsequently a Pneumatic Artificial Muscle design is proposed. A novel design of muscle end fixtures is presented which would allow the muscle to operate at a gage pressure surpassing 2.76 MPa (i.e. 400 psi) and yield a muscle force that is at least 3 times greater than that produced by any existing equivalent Pneumatic Artificial Muscle. Finally, the proposed Pneumatic Artificial Muscle is tested and validated to verify that it meets the size, weight, kinetic and kinematic requirements of human knee articulation.

Ce mémoire présente les efforts effectués pour réduire l'angle de perte de couches de pentoxyde de tantale amorphes telles qu'utilisées pour les miroirs de LIGO. Afin d'améliorer le niveau de relaxation des couches, celles-ci ont été déposées par pulvérisation cathodique magnétron à des températures allant de 50 °C à 480 °C, elles ont subi un recuit thermique rapide, elles ont été implantées par des ions d'oxygène, elles ont été déposées par pulvérisation cathodique magnétron en appliquant une tension de polarisation sur le substrat lors du dépôt allant de 0 V à -450 V et elles ont été déposées par pulvérisation cathodique magnétron pulsée à haute puissance dans le cadre de différentes expériences. L'angle de perte, l'épaisseur, la rugosité, l'indice de réfraction, la composition atomique, la contrainte, l'état de relaxation et le module de Young des couches ont par la suite été trouvés à l'aide de l'ellipsométrie spectralement résolue, la spectrométrie de rétrodiffusion de Rutherford, la détection des reculs élastiques, la spectroscopie Raman, la diffraction de rayons X et la nano-indentation. Il a été trouvé que la température de dépôt améliorait légèrement le degré de relaxation des couches jusqu'à 250 °C, mais qu'elle avait peu d'impact après recuit. Aussi, lors de dépôt à température de la pièce, une forte tension de polarisation réduit l'angle de perte, mais cet effet est encore une fois perdu suite au recuit. Les autres méthodes mentionnées ci-dessus n'ont pas influencé le degré de relaxation des couches selon l'angle de perte, la spectroscopie Raman et la diffraction de rayons X. Cette recherche a été réalisée avec le support financier du CRSNG et du FRQNT (numéro de dossier 206976). / This master's thesis presents the experiments made to reduce the loss angle of tantala coatings similar to those used in LIGO. To improve the relxation level of the coatings they were deposited by magnetron sputtering at temperatures varying from 50 °C to 480 °C. They were also subjected to rapid thermal annealing, and oxygen implantation. In another experiment, the coatings were deposited by magnetron sputtering with substrate biasing varying from 0 V to -450 V at room temperature and at 250 °C. Finally, the coatings of tantala were deposited by high power impulse magnetron sputtering. The loss angle, thickness, roughness, refractive index, atomic composition, stress, the relaxation state and Young's modulus of the coatings were characterized using spectroscopic ellipsometry, Rutherford backscattering, elastic recoil detection, Raman spectroscopy, X-ray diffraction and nanoindentation. It was found that the deposition temperature improved the loss angle until it reached 250 °C. However, annealing the coatings had a superior impact and the influence of the deposition temperature was not visible after annealing. When was applied a high bias to the susbtrate at room temperature, the obtained coating was slightly more relaxed than when a low bias was applied but this effect is, once again, insignificant after annealing. The other methods of deposition mentioned did not improve the loss angle or modify the relaxation state found by Raman spectroscopy and X-ray diffraction of the tantala coatings. This research was made with the financial support of the NSERC and of the FRQNT (file number 206976).

This diploma thesis is focused on studying the influence of different types of surface treatments on vibropressed product. The main goal is to characterize surface treatments consisting of application of surface coatings that are hardened by infrared or ultraviolet radiation. Theoretical part gives specifications already known methods for surface finishing. Briefly describes selected types of prefabricated concrete parts and specificate the requirements for these products. It also describes used test methods. The experimental part was aimed at establishing the effectiveness of changing properties concrete products by adding coatings on their surface. This was achieved by testing the properties of concrete paving blocks with modified surfaces and testing of reference blocks that did not have any surface treatment followed by mutual comparison of the results.

En 2015, le Laser Interferometer Gravitational-Wave Observatory (LIGO) a observé pour la première fois des ondes gravitationnelles générées par la fusion de deux trous noirs. Cette observation résulte de 40 ans d’efforts afin de réduire au minimum les sources de bruit qui affectent l’interféromètre. À ce jour, la sensibilité de LIGO, dans son domaine de fréquence le plus sensible, est limitée par la granularité de la lumière d’une part et, d’autre part, par un phénomène de fluctuations thermiques résultat de la dissipation mécanique dans les couches minces qui constituent ses miroirs, en particulier dans le matériau ayant un haut indice de réfraction : l’oxyde de tantale. Une amélioration de la sensibilité permettrait d’observer davantage d’événement, d’autres phénomènes gravitationnels, ainsi que des détails importants permettant de mieux les comprendre. Ce mémoire présente les résultats de nos recherches afin de diminuer le bruit causé par la dissipation mécanique interne dans les couches à haut indice de réfraction. Pour ce faire, des couches d’oxyde de tantale ont été dopées soit au zirconium ou à la fois au zirconium et au titane, par co-dépôt. Des couches avec différentes quantités de dopant ont été synthétisées par pulvérisation cathodique magnétron sur des substrats de silice semblables à ceux de LIGO. Par la suite, la dissipation mécanique, l’épaisseur, la rugosité, la composition, la densité surfacique, et la microstructure ont été caractérisées par suspension nodale, ellipsométrie résolue spectralement, spectrométrie de rétrodiffusion de Rutherford et la spectroscopie Raman. Il appert que le zirconium permet d’augmenter la température de recuit avant la cristallisation, ce qui permet de diminuer plus amplement la dissipation mécanique interne, mais ne change pas la dissipation à une température de recuit donnée. Il a aussi été déterminé que la concentration de titane permettait de diminuer l’angle de perte, peu importe la concentration de zirconium. Une combinaison des deux dopages et un recuit à haute température permet ainsi de recuire par un facteur d’environ 1.5 la dissipation mécanique interne. La différence de coefficient d’expansion thermique durant les recuits à haute température induit cependant des problèmes de craquement des couches, partiellement résolus par l’application d’une couche de recouvrement en silice. / In 2015, the Laser Interferometer Gravitational-Wave Observatory (LIGO) observed for the first time gravitational waves generated by the merger of two black holes. This observation was the resut of 40 years of efforts to minimize the noise source which affect the the interferometer. To this date, the sensitivity of LIGO, in its most sensitive frequency domain, is limited by the granularity of the light on one hand, on the other, by a phenomenon of thermal fluctuations resulting from the mechanical dissipation in the thin film of the miroir, in particular in the high refractive index material: tantala. An improvement of the sensitivity would allow the measurement of more events, other gravitational phenomena and some details that would result in a better understanding. This master’s thesis presents results of our research to reduce the noise caused by internal mechanical dissipation in high refractive index layers. To do so, tantala layers were doped with either zirconium and titanium by co-deposition. Layers with different amounts of dopant were synthesized by magnetron sputtering on fused silica substrate similar to those of LIGO. Subsequently, mechanical dissipation, thickness, roughness, composition, areal density and microstructure were characterized by gentle nodal suspension, spectrally resolved ellipsometry, Rutherford backscattering spectroscopy, and Raman spectroscopy. It appears that zirconium allows the annealing temperature to be increased before crystallization which further decreases internal mechanical dissipation, but does not change dissipation at a given annealing temperature. It was also determined that the concentration of titanium reduced the loss angle regardless of the zirconium concentration. A combination of the two dopant and high annealing temperatures thus enables the internal mechanical dissipation to be lower by a factor of 1.5.The difference in thermal expansion coefficient during high temperature annealing, however, induces layer cracking problems, partially resolved by the application of a silica cap.

This master's thesis deals with design of D class audio final amplifier, which was output power 400 W for 4 ? load impedance. Designed audio amplifier is specifical for active speaker, which consists of satelite speakers and subwoofer. Further more it deals also with other functional blocks, e.g. balanced input preamplifier, active crossover and protection for safety running. Outcome of this work are schemes of each functional blocks of D class audio amplifier, whose functionality was verified by simulation. Thesis also contains full reference material including mechanical arrangement of functional blocks on printed connection board. The conclusion contains the measured parameters of function blocks of produced prototype and complete photographic documentation.

This project deals with design and implementation of control system, which is used for regulation climate conditions in special grow box. Measured values are displayed on graphic LCD, sent to application in PC or displayed on web server. The project solves software and hardware implementation of measurement system.

Breitstreifenlaser haben eine breite Emissionsapertur, die es ermöglicht eine hohe Ausgangsleistung zu erreichen. Gleichzeitig führt sie jedoch zu einer Verringerung der lateralen Strahlqualität und zu ihrem nicht-stationären Verhalten. Forschung in diesem Gebiet ist anwendungsgetrieben und somit ist das Hauptziel eine Erhöhung der Brillanz, die sowohl die Ausgangsleistung als auch die laterale Strahlqualität beinhaltet. Um die zugrunde liegenden raumzeitlichen Phänomene zu verstehen und dieses Wissen zu nutzen, um die Kosten der Brillanz-Optimierung zu minimieren, ist ein selbst-konsistentes Simulationstool notwendig, welches die wichtigsten Prozesse beinhaltet. Zunächst wird in dieser Arbeit ein quasi-dreidimensionales elektro-optisch-thermisches Model präsentiert, welches wesentliche qualitative Eigenschaften von realen Bauteilen gut beschreibt. Zeitabhängige Wanderwellen-Gleichungen werden genutzt, um die inhärent nicht-stationären optischen Felder zu beschreiben, welche an eine Ratengleichung für die Überschussladungsträger in der aktiven Zone gekoppelt sind. Das Model wird in dieser Arbeit um eine Injektionsstromdichte erweitert, die laterale Stromspreizung und räumliches Lochbrennen korrekt beschreibt. Des Weiteren wird ein Temperaturmodel präsentiert, das kurzzeitige lokale Aufheizungen in der Nähe der aktiven Zone und die Formierung einer stationären Temperaturverteilung beinhalten. Im zweiten Teil wird das beschriebene Modell genutzt, um die Gründe von Brillanz-Degradierung, das heißt sowohl die Ursprünge der Leistungssättigung als auch des nicht diffraktionslimitierten Fernfeldes zu untersuchen. Abschließend werden im letzten Teil Laserentwürfe besprochen, welche die laterale Brillanz verbessern. Hierzu gehört ein neuartiges “Schachbrettlaser” Design, bei dem longitudinal-laterale Gewinn-Verlust-Modulation mit zusätzlicher Phasenanpassung ausgenutzt wird, um eine sehr geringe Fernfeld-Divergenz zu erhalten. / Broad-area lasers are edge-emitting semiconductor lasers with a wide lateral emission aperture that enables high output powers, but also diminishes the lateral beam quality and results in their inherently non-stationary behavior. Research in the area is driven by application and the main objective is to increase the brightness which includes both the output power and lateral beam quality. To understand the underlying spatio-temporal phenomena and to apply this knowledge in order to reduce costs for brightness optimization, a self-consistent simulation tool taking into account all essential processes is vital. Firstly, in this work a quasi-three-dimensional opto-electronic and thermal model is presented, that describes well essential qualitative characteristics of real devices. Time-dependent traveling-wave equations are utilized to describe the inherently non-stationary optical fields, which are coupled to dynamic rate equations for the excess carriers in the active region. This model is extended by an injection current density model to accurately include lateral current spreading and spatial hole burning. Furthermore a temperature model is presented that includes short-time local heating near the active region as well as the formation of a stationary temperature profile. Secondly, the reasons of brightness degradation, i.e. the origins of power saturation and the spatially modulated field profile are investigated and lastly, designs that mitigate those effects that limit the lateral brightness under pulsed and continuous-wave operation are discussed. Amongst those designs a novel “chessboard laser” is presented that utilizes longitudinal-lateral gain-loss modulation and an additional phase tailoring to obtain a very low far-field divergence.

With the rapid growth of air travel, concerns about the emissions of greenhouse gas emissions resulting from the air transportation sector are growing. Although the current battery technologies might not be adequate for all-electric regional aircraft, the energy density of the current battery technologies could be adequate to electrify light-sport aircraft used for training and recreation. Due to the nature of the propeller load and noise isolation of the cabin, switched reluctance motors can be an excellent candidate for the propulsion system of electrified light-sport aircraft. The proposed SRM is designed to replace a 70 kW permanent magnet synchronous motor used in the aerospace industry with similar volume constraints and operational requirements. In order to meet the high-power density requirements of this application, a design framework is proposed which includes several layers of the design process. The design objectifies are the average torque, torque ripple, and radial forces by integrating the control and geometry design into the proposed framework. A comprehensive design process is carried out with the proposed framework, and a detailed coil design process is performed. The rotor cut-outs are designed to reduce the weight of the motor. The thermal performance of the motor has been analyzed for the calculated motor losses and the cooling system constraints. / Thesis / Master of Applied Science (MASc)