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This work is an investigation into the curvature related potential for flux to flow in the radial direction in the back-iron of laminated axial flux machine cores. Analytical and numerical models are presented. Analysis based on these models has shown that, in practical axial flux machines, the radial component of the flux density can be neglected with respect to the flux density distribution in the core back-iron. It has also been found that if the core permeability, core conductivity and number of poles are sufficiently high then power loss due to curvature related cross-lamination flux is negligible compared to normal eddy current losses. A closed form expression to predict losses due to curvature related radial flux is also presented. This expression allows axial flux machine designers to make quick assessment of the need to consider these losses when designing axial flux machines.

Real-time digital simulation of electrical machines and drives is an efficient approach to evaluate the true behavior of newly designed machines and controllers before applying them in a real system. State-of-the-art real-time digital simulators aim to offer a precise replica for different parts of an electrical drive. By the aid of these powerful simulators and hardware-in-the-loop (HIL) simulation, design engineers are able to test their new controllers or machines against a virtual motor drive which has been previously modeled and tested off-line. Interaction between different parts of the electrical drive, especially under hazardous and abnormal conditions, can then be studied in a cost-effective manner. Although many studies about the optimized models of power electronic drives and digital controllers for real-time simulation have been done, the real-time models of electrical machines are still limited to the lumped parameter electric circuit models. This is mainly due to the complexity of a detailed electrical machine model which makes it computationally expensive. In this thesis geometrical real-time permeance network models (PNMs) of induction machines are developed which can accommodate the local phenomena inside an electric machine such as saturation and slotting. For this purpose, numerical methods inside the model are optimized to reduce the computation time. Novel nonlinear solution algorithms are also developed to address the problem of real-time simulation of nonlinear systems. Next, the proposed model is linked with other parts of an electric drive to develop a PNM-based real-time induction motor drive. A comparison of the results obtained through real-time simulation and experiment shows their agreement. / Power Engineering and Power Electronics

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>Magister Scientiae - MSc / Over the past 5 years, South Africa has been experiencing a severe drought. This has caused industrial and agricultural processes, to compete for a limited supply of water. Since the economy relies mostly on agricultural activities, water consumption by industrial processes is taking its toll. One of these processes is the introduction of wet flue gas desulphurization (FGD) treatment at Eskom coal fired power stations. This dissertation explores the possibility of using membrane technology as a means of water recovery after the coal combustion flue gas has been treated with wet FGD. A lab-scale permeance testing system was specially built and modified to have complete thermal control of the environment inside the system. The permeance testing system produced a gas, similar to that of a wet FGD treated flue gas, which was then tested. A tubular lab-scale membrane module was designed and produced for the permeance testing system. The permeance figures of both Nitrogen gas and water vapour were determined for the membrane used in module production. These figures coincided with figures provided by the supplier, which warranted successful permeance testing. After success of the lab-scale testing, the data was used to design and develop a pilot-scale membrane module. This module was designed to meet pre-determined requirements as set forth by the project team. Producing lab-scale membrane modules helped identify and address possible problems in pilot-scale module design. This lead to the successful design and construction of a pilot-scale membrane module that could be used to recover the water that is needed to run the wet FGD process.

>Magister Scientiae - MSc / The production procedure of a CsHS04-Si02 composite membrane was optimized in order to obtain the highest possible H2:C02 and H2:C~ Idea selectivity permeance. The optimized membrane preparation procedure led to the preparation of membranes with Idea selectivity of 5 and 10 towards H2:C~ and H2:C02 respectively. The H2 permeance value is on average 0.15 umol- s-l·m-2.Pa-I. The reproducibility of the optimized membrane was further investigated and was found to be satisfactory. An attempt was made to discover the gas transport mechanism of H2, C~ and C02. Gas permeance measurements were carried out as a function of time and temperature (between 25-180°C) using H2, C~ and C02 as analyte gases. XRD, TGA and impedance spectroscopy were used to identify the phases of CsHS04 within the membrane. The gas permeation mechanism was found to be a combination of Knudsen diffusion and solution diffusion. The pores that allow Knudsen diffusion (allow transport of Hi, CH4 and C02) are believed to be located at the CSHS04 crystal phase boundaries. In parallel, H2 diffuses selectively through the lattice of phase II/III of CsHS04 ..

Les machines à commutation de flux cinq-phases présentent une tolérance aux pannes et une robustesse qui les rendent très intéressantes dans un point de vue de la fiabilité, comme montré dans le premier chapitre.Dans ces travaux de thèse nous avons explorés la possibilité de détecter les défauts qui affectent cette machine par la signature des vibrations générées dans la machine.En utilisant les outils physiques et mathématiques présentés dans le deuxième chapitre, nous avons construit deux modèles multiphysiques, un modèle aux les éléments finis développé dans le troisième chapitre et un modèle analytique, appelé aux réseaux de perméances, dans le quatrième chapitre.Le comportement vibratoire de la machine a été étudié à l'aide de ces deux modèles, en régimesain et en défaut afin de connaitre comment ce comportement est influencé par les grandeurs électriques et magnétiques de la machine.Par ailleurs nous avons étudié la possibilité de détecter et discriminer les différents types de défauts.Le modèle analytique se présente comme un bon estimateur du comportement en défaut de la machine, malgré ses écarts avec la simulation.Dans le cinquième chapitre, les deux modèles multiphysiques ont été validés par des essais expérimentaux et nous avons pu expliquer le comportement en défaut d’un point de vue mécanique plutôt que magnétique.Enfin, dans le sixième chapitre, nous avons utilisé les deux modèles pour étudier le comportement en défaut de la machine, à des vitesses au-dessus de la limite expérimentale (3100 tr/min). / Five-phase flux switching machines have a fault tolerance and robustness that makes them very interesting from the point of view of reliability, as shown in chapter one of this work. In our studies we have explored the possibility of detecting faults that affect this type of machine using the signature of stator vibrations.Using the physical and mathematical tools presented in chapter two, we improved two multyphisics models, one based on finite elements method that it's presented in chapter three and the seconde one analitycal model, called permeance networks, in chapter four. The vibratory behavior of the machine was studied using these two models, under healthy and faulty conditions, in order to know how this behavior is influenced by the electrical and magnetic magnitudes of the machine. In addition, we have studied the possibility of detecting and discriminating different types of faults. Analytical model is a good estimator of fault behavior of the machine, despite its differences with the simulation.In chapter five, the two multiphysical models have been validated by experimental tests and we have been able to explain fault behavior by mechanical origin rather than magnetic origin.Finally, in chapter six, we used both models to study the fault behavior of the machine, at speeds above the experimental limit (3100 rpm).

Modified nanocellulose have distinctive qualities and have drawn a lot of interest from a variety of fields. It is a natural, sustainable product that is manufactured from plant-based materials like wood and other renewable resources. It is also biodegradable. It is a possible material for battery separators because of its great mechanical strength, flexibility, and ability to create a stable and consistent membrane. Due to the cost of using it as a membrane, it has been investigated in this work to see if it can be coated onto a substrate and used as battery separator. In this work sulfonated cellulose nanofibrils (SCNF) has been used to be coated on kraft paper and inkjet paper using a rod coater. Parameters like concentration, thickness and substrates have been varied in this experiment. Viscosity was measured using Brookfield instrument to measure the viscosity for 0,5% SCNF and 1,5% SCNF. The coating was carried out using a rod coater and varying between two rods to influence the thickness, the coating used concentrations of 0,5% SCNF and 1,5% SCNF and two different substrates, kraft paper and inkjet paper. Thickness was determined to study the effect of the variation in rod. The mechanical strength was tested on the coated paper substrates and compared the results to the noncoated substrates as reference, the mechanical strength showed an improvement with the coated SCNF substrates. Permeance through the Gurley method was studied in order to understand how the coated substrates behaves compared to the noncoated. Contact angle was determined as well to understand the wettability of the coated substrates and how they would behave as separators in zinc ion batteries. The contact angle decreased with increasing concentration of the SCNF which is a result of the sulfonate groups. Cross sections were analyzed using SEM to study the influence of the coating to the substrates. Ionic conductivity was also tested to evaluate the possibility of the coated substrates as separators.

We are provided countless products from the forest industry and has been through many years. Paper, paper board, packaging materials and furniture to mention a few. A special type of paper used in food packaging for example, is greaseproof paper. Many producers of greaseproof papers use the toxic and harmful group of chemicals called per- and polyfluorinated alkyl substances (PFAS) in coating since they possess grease resistance. Nordic Paper is a manufacturer of iamKraft® kraft paper and greaseproof paper with over a hundred years of experience without the use of PFAS. Without PFAS, they instead rely on excess refining to form a very dense paper. Nordic Paper has decided to introduce the addition of eucalyptus fibers to the softwood sulfate pulp to enhance the formation of the paper. This study aims to investigate the effects of ~20% addition of eucalyptus fibers to softwood sulfate pulp in regard to refiner energy expended, air permeance (as a measure of grease resistance) and formation. Laboratory work has been done on hand made sheets with a vacuum suction box in laboratory scale. Eight different pulps (four with addition of eucalyptus), provided from Nordic Paper Seffle AB, Säffle, with different refining degree was used in this study. The vacuum pressure used was 20 kPa through all tests, with dwell times 0, 1, 2.5, 5, 10, and 20 ms on sheets with a grammage of 50 g/m2. The study has shown that the pulp with ~20% addition of eucalyptus achieved 86°SR with only 82% expended energy relative to the softwood pulp, which had a refining degree of 87°SR. This small difference in refining degree led to a similar development in dewatering after 20 ms dwell time and 20 kPa, where the softwood pulp achieved a dryness of 9.2% and the pulp with addition of eucalyptus achieved 9.0% dryness. The formation of the softwood pulp was worse, which was the reason for the implementation of addition of eucalyptus. The air permeance on the other hand was not improved by the eucalyptus, but more data is needed to confirm since it is based on only one occasion. So, if the air permeance (grease resistance) allows, Nordic Paper Seffle AB may be able to save 20% in expended energy for refining of softwood sulfate pulp with addition of eucalyptus. / Vi tillhandahåller otaliga produkter från skogsindustrin och har gjort i många år. Papper, kartong, förpackningsmaterial och möbler för att nämna några. En speciell typ av papper som används i till exempel livsmedelsförpackningar är fettresistent papper. Många tillverkare av dessa papper använder den giftiga och skadliga gruppen av kemikalier som kallas per- och polyfluorerade alkylämnen (PFAS) i beläggning eftersom de har fettbeständiga egenskaper. Nordic Paper är en tillverkare av iamKraft® kraftpapper och ”greaseproofpapper” med över hundra års erfarenhet utan användning av PFAS. Utan PFAS förlitar de sig istället på extra malning av fibrer för att bilda ett mycket tätt papper. Nordic Paper har beslutat att införa tillsats av eukalyptusfibrer till sulfatmassa av barrved för att förbättra formationen på papperet. Denna studie syftar till att undersöka effekterna av ~20 % tillsats av eukalyptusfibrer till barrsvedssulfatmassan med avseende på förbrukad malningsenergi, luftpermeans (som ett mått på fettbeständighet) och formation. Laborationer har utförts på handgjorda ark med vakuumsuglåda i laboratorieskala. Åtta olika massor (fyra med tillsats av eukalyptus), tillhandahållna från Nordic Paper Seffle AB, Säffle, med olika malningsgrad användes i denna studie. Vakuumtrycket som användes var 20 kPa genom alla tester, med uppehållstider 0, 1, 2.5, 5, 10 och 20 ms på ark med en ytvikt på 50 g/m2. Studien har visat att massan med ~20% tillsats av eukalyptus uppnådde 86°SR med endast 82% förbrukad energi i förhållande till sulfatmassan, som hade en malningsgrad på 87°SR. Denna lilla skillnad i malningsgrad ledde till en liknande utveckling i avvattning efter 20 ms uppehållstid och 20 kPa, där sulfatmassan uppnådde en torrhalt på 9.2% och massan med tillsats av eukalyptus uppnådde 9.0% torrhalt. Formationen på sulfatmassan var sämre, vilket var anledningen till genomförandet av tillsats av eukalyptus. Luftpermeansen å andra sidan förbättrades inte av eukalyptusen, men mer data behövs för att bekräfta detta eftersom den enbart är baserad på ett enda tillfälle. Så om luftpermeansen (fettbeständigheten) tillåter kan Nordic Paper Seffle AB spara 20% i förbrukad energi för malning av barrvedssulfatmassa med tillsats av eukalyptus.

Les systèmes électriques embarqués dans l'aéronautique doivent satisfaire à des cahiers des charges de plus en plus exigeants portant sur le poids, les performances et la fiabilité, d'où l'utilisation des Machines Synchrones à Aimants Permanents (MSAP). Vu les contraintes imposées, les prototypes sont parfois assez éloignés d'une MSAP classique. La surveillance en ligne de ces systèmes est alors plus délicate mais représente un enjeu considérable vu l'aspect critique des applications (ailerons d'avion, freinage...) et a pour objectif d'éviter un incident majeur en le détectant puis en basculant sur un système identique redondé. Ce document propose un travail de modélisation de MSAP saine et en présence de défaut inter-spires ayant pour objectif de définir des méthodes de détections de défauts inter-spires en ligne, sans capteurs supplémentaires. Deux approches sont présentées pour modéliser les MSAP en présence de défauts inter-spires et sont comparées à des essais expérimentaux réalisés sur un prototype aéronautique. L'une d'entre elles, reposant sur une approche par Réseaux De Perméances (RDP), permet d'obtenir le meilleur compromis. La partie suivante propose de tester deux approches utilisant un indicateur de défaut basé sur un modèle d'Onduleur-MSAP sain et montre l'intérêt de ce type d'approche comparé à des approches plus classiques. L'ensemble des indicateurs développés est ensuite analysé à l'aide d'un outil utilisant la Reconnaissance de Formes (RDF) / Embedded 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)