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The electrification of automobiles has emerged as the sustainable powertrain solutionto meet United Nations sustainable development goals of sustainable cities andcommunities, affordable and clean energy, and climate action. The success of theelectrification depends on the efficiency of traction motors. Hence, the automobileindustry is dedicated to improving the performance of electrical traction machinesfor high performance and sustainability. The thesis aims to build various electricalmachine’s concept designs and quantify their behaviour on sustainability andperformance. The thesis objective is to design Permanent Magnet Synchronous Motor (PMSM),Synchronous Reluctance Motor (SynRM), and Permanent Magnet SynchronousReluctance Motor (PM­SynRM). The thesis work comprises of accurate performanceestimation and optimisation of these electrical machines through a finite element based method. The in­house scripts are developed to estimate the performance, electrical losses, and efficiency of these electrical machines through flexible open-source tools. The performance of PMSM with rare-­earth magnet Neodymium Ferrite Boron(NdFeB) and without rare­-earth magnet (ferrite) is done to evaluate the role of bothmagnets in producing torque density. The SynRM is evaluated and optimized usinggenetic algorithms in the thesis. The electrical machines are designed without the useof rare-­earth magnets to eliminate the degradation of the environment and reduce thecost and weight of the motor. / The electrification of automobiles has emerged as the sustainable powertrain solutionto meet United Nations sustainable development goals of sustainable cities andcommunities, affordable and clean energy, and climate action. The success of theelectrification depends on the efficiency of traction motors. Hence, the automobileindustry is dedicated to improving the performance of electrical traction machinesfor high performance and sustainability. The thesis aims to build various electricalmachine’s concept designs and quantify their behaviour on sustainability andperformance. The thesis objective is to design Permanent Magnet Synchronous Motor (PMSM),Synchronous Reluctance Motor (SynRM), and Permanent Magnet SynchronousReluctance Motor (PM­SynRM). The thesis work comprises of accurate performanceestimation and optimisation of these electrical machines through a finite element based method. The in­house scripts are developed to estimate the performance, electrical losses, and efficiency of these electrical machines through flexible open-source tools. The performance of PMSM with rare-­earth magnet Neodymium Ferrite Boron(NdFeB) and without rare­-earth magnet (ferrite) is done to evaluate the role of bothmagnets in producing torque density. The SynRM is evaluated and optimized usinggenetic algorithms in the thesis. The electrical machines are designed without the useof rare-­earth magnets to eliminate the degradation of the environment and reduce thecost and weight of the motor.   Sammanfattning på svenska / Abstract in Swedish Elektrifieringen av bilar har framstått som en hållbar drivlinelösning för att mötaFörenade Nationernas hållbara utvecklingsmål för hållbara städer och samhällen, medprisvärda och rena energi och klimatåtgärder. Framgången med elektrifieringen berorpå effektivitet på motorer för framdrivningen. Därför är bilindustrin dedikerad tillatt förbättra prestanda för elmotorer för hållbarhet och hög prestanda. Avhandlingensyftar till att bygga olika konceptdesign för elmotorer för framdrivning och kvantifieraderas beteende på hållbarhet och prestanda. Uppsatsmålet är att utforma Permanent Magnet Synchronous Motor (PMSM),Synchronous Reluktance Motor (SynRM) och permanent magnetassisterad SynRM(PM­SynRM). Examensarbetet består av noggrann prestationsuppskattning ochoptimering av dessa elektriska maskiner genom finit element metod (FEM). Deskripten för att hantera FEM för elektormagnetisk design är in­house utveckladeför att uppskatta flexibelt prestanda, elektriska förluster och effektiviteten hos dessaelektriska maskiner genom att använda öppen källkod. Prestanda för PMSM med en sällsynta jordartsmagnet (NdFeB) och PMSM utansällsynta jordartsmagnet (ferrit) räknades fram för att utvärdera båda magneternasroll för att producera vridmomentdensitet. SynRM och PM­SynRM maskinernautvärderas och optimeras med hjälp av genetiska algoritmer i avhandlingen.De studerade elektriska maskinerna är designad utan användning av sällsyntajordartsmagneter för att eliminera miljöförstöring och minska motorns kostnad ochvikt.

A new hybrid machine having variable reluctance and permanent magnets (PMs) is presented. The machine makes use of the features of a PM machine and variable reluctance machine. The resulting machine is doubly salient and has a structure free of flux reversals. Unlike conventional doubly salient permanent magnet machines (DSPMs), the one proposed in this report is driven by unipolar currents and uses an asymmetric converter which is used to drive switched reluctance machines. The reason to have a new hybrid machine without the drawbacks of conventional flux-reversal-free-stator SRMs and conventional DSPMs is also described. Conventional doubly salient permanent magnet machines which are driven by alternating currents, do not use reluctance torque and have flux reversals in the stator iron. Homopolar flux at the peak flux density lowers hysteresis and eddy-current loss, since the machine's core operates in only one magnetizing quadrant. Due to unbalanced forces in conventional stator-flux-reversal-free machines, their deployment in industrial and end-user applications has been hindered. The presented hybrid machine has balanced radial forces. Therefore, it maintains the advantages of conventional stator-flux-reversal-free machines while shedding its disadvantages. The proposed machine has significantly increased power density and is more electromechanically efficient than its predecessor. A experimental prototype motor has been designed and built. Its static torque characteristics correlated well with predicted data. Experimental operation of the drive under open loop speed control shows the efficiency to be 90.8% under non-ideal driving conditions. In the current energy conscious environment and market, this motor because of its high efficiency has a significant role in reducing the energy consumption in household, industrial and automotive applications requiring electric motors. / Ph. D.

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No description available.

A determinação das principais propriedades magnéticas de um ímã permanente geralmente requer sistemas de medição sofisticados e custosos. Este trabalho analisa e propõe um sistema de caracterização de ímãs permanentes de Terras Raras à temperatura ambiente de baixo custo e de implementação mais simples e rápida. Ele consiste de um circuito magnético formado pelo ímã permanente sob caracterização, uma culatra de aço, um entreferro variável e uma sonda de efeito Hall com seu respectivo gaussímetro para a medição da intensidade do campo magnético no entreferro. Como introdução se apresenta o estado da arte da caracterização dos ímãs permanentes, conceitos básicos de magnetismo e em relação aos ímãs permanentes, sua história, os principais tipos, sua importância e suas aplicações principais. Os resultados teóricos e experimentais são comparados a resultados certificados, validando o método como proposto. / Determining the main magnetic properties of a permanent magnet usually requires sophisticated and expensive measurement setups. This work analyses and proposes a low-cost system to characterize Rare Earth permanent magnets at ambient temperature with easy and fast implementation. It consists of a magnetic circuit with the permanent magnet under test, appropriate pole pieces, a variable air gap and a Hall Effect probe with its respective Gaussmeter. As an introduction, it is presented the state of the art of permanent magnets characterization, basic concepts of magnetism and its history, the main types of permanent magnets, their importance and applications. The theoretical and experimental results are compared to certified ones, validating so the method as proposed.

This report explores example models from nine different operational areas found in the arts schools movement, examines the positive and negative impact of each, and attempts to draw cursory conclusions that could be applied to those seeking to evaluate an existing, or establish a new, arts school. The operational areas included in this report are the purpose of the school, size and scope, finances, governance and administration, faculty and staff, facilities, recruitment/auditions/retention, community involvement, and learning and information resources. Over the past four decades, arts-focused primary and secondary schools have been established to provide students with an alternative to traditional campuses across the country using a variety of operational models and tactics for success but there has been limited documentation of their effectiveness. This report seeks to begin the establishment of such documentation. / text

The number of people suffering from neurodegenerative diseases, such as Alzheimer`s disease, increased dramatically over the past centuries and is expected to increase even further within the next years. Based on predictions of the World Health Organization and Alzheimer`s Disease International, 115 million people will suffer from dementia by the year 2050. An additionally increase in other age related neurodegenerative diseases is also forecasted. Quite naturally, neurodegenerative diseases became a focus of attention of governments and health insurances, trying to control the uprising financial burden. Early detection and treatment of neurodegenerative diseases could be an important component in containing this problem. In particular, researchers focused on automatic methods to analyze patients’ imaging data. One way to detect structural changes in magnetic resonance images (MRI) is the voxel-based method approach. It was specifically implemented for various imaging modalities, e.g. T1-weighted images or diffusion tensor imaging (DTI). Voxel-based morphometry (VBM), a method specifically designed to analyze T1-weighted images, has become very popular over the last decade. Investigations using VBM revealed numerous structural brain changes related to, e.g. neurodegeneration, learning induced structural changes or aging. Although voxel-based methods are designed to be robust and reliable structural change detection methods, it is known that they can be influenced by physical and physiological factors. Dehydration, for example, can affect the volume of brain structures and possibly induce a confound in morphometric studies. Therefore, three-dimensional T1-weighted images were acquired of six young and healthy subjects during different states of hydration. Measurements during normal hydration, hyperhydration, and dehydration made it possible to assess consequential volume changes in gray matter (GM), white matter (WM), and cerebrospinal fluid (CSF). The datasets were analyzed using VBM, FreeSurfer and SIENA. A significant decrease of GM and WM volume, associated with dehydration, was found in various brain regions. The most prominent effects were found in temporal and parietal areas, in the left inferior orbito-frontal region, and in the extra-nuclear region. Moreover, we found consistent increases in CSF, an expansion around 6% of the ventricular system affecting both lateral ventricles, i.e. the third and fourth ventricle. Similar degrees of shrinkage in WM volume and increase of the ventricular system have been reported in studies of Alzheimer’s disease during disease progression and in its prestage mild cognitive impairment. Based on these findings, a potential confound in GM and WM or CSF studies due to the subjects’ hydration state cannot be excluded and should be appropriately addressed. These results underline the sensitivity of VBM and might also concern other voxel-based methods, such as Tract-Based Spatial Statistics (TBSS). TBSS was specifically designed for WM analyses and its sensitivity might be helpful for revealing the spatial relation of structural WM changes and related blood serum biomarkers. Two common brain related biomarkers are the glial protein S100B, a plasticity inducing neuro- and gliotrophin, and neuron-specific enolase (NSE), a marker for neuronal damage. However, the spatial specificity of these biomarkers for brain region has not been investigated in vivo until now. Therefore, we acquired two MRI parameters – T1- weighted and DTI - sensitive to changes in GM and WM, and obtained serum S100B and NSE levels of 41 healthy subjects. Additionally, the gene expression of S100B on the whole brain level in a male cohort of three subjects from the Allen Brain Database was analyzed. Furthermore, a female post mortal brain was investigated using double immunofluorescence labeling with oligodendrocyte markers. It could be shown that S100B is specifically related to white matter structures, namely the corpus callosum, anterior forceps and superior longitudinal fasciculus in female subjects. This effect was observed in fractional anisotropy and radial diffusivity – the latest an indicator of myelin changes. Histological data confirmed a co-localization of S100B with oligodendrocyte markers in the human corpus callosum. S100B was most abundantly expressed in the corpus callosum according to the whole genome Allen Human Brain Atlas. In addition, NSE was related to gray matter structures, namely the amygdala. This effect was detected across sexes. The data demonstrates a very high S100B expression in white matter tracts, in particular in human corpus callosum. This was the first in vivo study validating the specificity of the glial marker S100B for the human brain, and supporting the assumption that radial diffusivity represents a myelin marker. The results open a new perspective for future studies investigating major neuropsychiatric disorders. All above mentioned studies are mainly dependent on the sensitivity and accuracy of soft and hardware parameters. In particular, technical developments have improved acquisition accuracy in the field of MRI. Interestingly, very little is known about the confounding effects of variations due to hardware parameters and their possible impact on reliability and sensitivity of VBM. Recent studies have shown that different acquisition parameters may influence VBM results. Therefore age-related GM changes were investigated with VBM in 36 healthy volunteers grouped into 12 young, 12 middle-aged and 12 elderly subject. Six T1-weighted datasets were acquired per subject with a 12-channel matrix coil, as well as a 32-channel array, MP-RAGE and MP2RAGE, and with isotropic resolutions of 0.8 and 1 mm. DARTEL-VBM was applied on all images and GM, WM and CSF segments were statistically analyzed.. Paired t-tests and statistical interaction tests revealed significant effects of acquisition parameters on the estimated gray-matter-density (GMD) in various cortical and subcortical brain regions. MP2RAGE seemed slightly less prone to false positive results when comparing data acquired with different RF coils and yielded superior segmentation of deep GM structures. With the 12-channel coil, MP-RAGE was superior in detecting age-related changes, especially in cortical structures. Most differences between both sequences became insignificant with the 32-channel coil, indicating that the MP2RAGE images benefited more from the improved signal-to-noise ratio and improved parallel-imaging reconstruction). A possible explanation might be an overestimation of the GM compartment on the MP-RAGE images. In view of substantial effects obtained for all parameters, careful standardization of the acquisition protocol is advocated. While the current investigation focused on aging effects, similar results are expected for other VBM studies, like on plasticity or neurodegenerative diseases. This work has shown that voxel-based methods are sensitive to subtle structural brain changes, independent of imaging modality and scanning parameters. In particular, the studies investigated and discussed the analysis of T1- and diffusion weighted images with VBM and TBSS in the context of dehydration, blood serum sensitive biomarkers and aging were discussed. The major goal of these studies was the investigation of the sensitivity of voxel-based methods. In conclusion, sensitivity and accuracy of voxelbased methods is already high, but it can be increased significantly, using optimal hardand software parameters. It is of note, though, that these optimizations and the concomitant increase of detection sensitivity could also introduce additional confounding factors in the imaging data and interfere with the latter preprocessing and statistical computations. To avoid an interference e.g. originating from physiological parameters, a very careful selection and monitoring of biological parameters of each volunteer throughout the whole study is recommended. A potential impact of scanning parameters can be minimized by strict adherence to the imaging protocol for each study subjectwithin a study. A general increase in detection sensitivity due to optimized parameters selection in hard- and/or can not be concluded by the above mentioned studies. Although the present work addressed some of those issues, the topic of optimal selection of parameters for morphometric studies is still very complex and controversial and has to be individually decided. Further investigations are needed to define more general scanning and preprocessing standards to increase detection sensitivity without the concomitant amplification of confounding factors.

Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2011. / ENGLISH ABSTRACT: In this study a new type of gearless, direct-drive wind generator, which can be connected directly to the grid, is proposed. The working characteristics of this generator are based upon the principles of the permanent magnet induction generator (PMIG). By omitting the need for a gearbox and power electronic converter this generator type has several advantages regarding cost and reliability. Although the PMIG is proposed in previous studies as favourable for wind power generation, the mechanical complexity and difficult construction associated with these types of generators, seems to be the main reason why these generator systems are not used. The design methods presented in this study are intended to alleviate these constructional issues by proposing the split-PMIG (S-PMIG), where the stator winding and the induction cage-rotor windings are electromagnetically separated. The machine is basically split into two permanent magnet (PM) machines, a grid connected synchronous generator (SG) unit and a turbine connected induction generator (IG) unit. These two units are mechanically linked by a common PM-rotor. To evaluate this concept a finite element (FE) design analysis is done independently for both machine components. The emphasis of the design optimisation is the minimisation of the cogging torque, while still having a decent performing, easily constructible generator. This generator should also have low load ripple content. Cogging torque can result in the failure of the turbine to start up, especially at low wind speeds. As this is a directly grid connected generator, torque ripple transferred to the common PM-rotor can destabilise the generator. Based upon the FE designs a preliminary S-PMIG system is constructed and practically evaluated. Due to the modular nature of the design it is possible to implement the synchronous generator part of the S-PMIG in conjunction with a grid-connected solid state converter (SSC). This allows for a useful comparison with the S-PMIG system. Promising results are obtained from initial tests of the S-PMIG directly connected to the grid. It is shown that the operation of this generator is stable under a wide range of wind load conditions. However, some important machine design issues are identified from these practical results, which could prove vital in the implementation of future S-PMIG designs. / AFRIKAANSE OPSOMMING: In hierdie studie word 'n nuwe ratkaslose direk-aangedrewe wind generator voorgestel, wat direk aan die krag netwerk gekoppel kan word. Hierdie generator is gebaseer op die beginsels waarop permanente magneet induksie generators (PMIG’s) werk. Deur die ratkas en drywings-elektroniese omsetter uit te laat, het hierdie generator verskeie voordele rakende koste en betroubaarheid. Alhoewel vorige studies hierdie generator voorstel as 'n belowende opsie vir gebruik in wind-energie-stelsels, lyk dit of die meganiese kompleksiteit en moeilike konstruksie die hoof rede is hoekom hierdie generator stelsels tans nie gebruik word nie. Die ontwerpsmetodes wat in hierdie studie voorgestel word poog om die genoemde konstruksie probleme op te los deur die gesplete-PMIG (S-PMIG), waar die stator wikkelings en die induksie masjien kou-rotor wikkelings elektromagneties ontkoppel is, voor te stel. Hierdie masjien is basies verdeel in twee permanente magneet (PM) masjiene, 'n netwerk gekoppelde sinchroongenerator (SG) eenheid en 'n turbine gekoppelde induksie generator (IG) eenheid. Hierdie twee eenhede word gekoppel deur 'n gemeenskaplike PM-rotor. Om hierdie konsep te evalueer word eindige element analise onafhanklik vir beide masjiene gedoen. Die fokus van die ontwerp optimering is die minimalisering van die vertandingsdraaimoment, terwyl die generator steeds goed presteer en maklik is om te vervaardig. Vertandingsdraaimoment kan tot die gevolg hê dat die turbine versuim om te begin draai, veral by lae windsnelhede. Dit is ook belangrik dat die generator 'n lae rimpel inhoud onder las bevat. Omrede hierdie generator direk aan die netwerk gekoppel is, kan draaimoment pulsasies, oorgedra aan die gemeenskaplike PM-rotor, die masjien destabiliseer. Gebaseer op die eindige element ontwerpe, is 'n voorlopige gesplete-PMIG gebou en prakties geëvalueer. As gevolg van die modulêre struktuur van die ontwerp, is dit moontlik om die SG gedeelte van die gesplete- PMIG saam met 'n drywings-elektroniese omsetter te implementeer. Dit laat toe vir 'n nuttige vergelyk tussen die twee stelsels. Belowende eerste toets resultate is verkry van die gesplete-PMIG direk gekoppel aan die netwerk. Daar word gewys dat hierdie generator stabiel oor 'n wye operasionele gebied kan funksioneer. Verskeie belangrike masjien ontwerpsfaktore word ook uitgelig met die praktiese evaluering van die gesplete-PMIG. Hierdie faktore kan uiters belangrik wees in die ontwerp en implementering van toekomstige gesplete-PMIG stelsels. / Sponsored by the Centre for Renewable and Sustainable Energy Studies