Thesis (MScEng)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: This thesis is a description of how the first magnetically geared axial flux permanent magnet generator (MGAFG) is designed, constructed and experimentally evaluated. Magnetic gears (MGs) allow for contact-less power transfer and lubricant free operation, which may solve the reliability concerns with current mechanically geared wind energy converters. However, the complex structure of MGs may present serious challenges to its design. Thus, special care should be given to the mechanical layout and the electromagnetic influence of every component. The MGAFG can be configured to be magnetically coupled or decoupled. In the coupled configuration the permanent magnets (PMs) of the MG contribute to the total flux linkage in the PM generator (PMG). The coupled configuration is therefore more efficient. The processing time required to optimise the decoupled configuration is however much faster, since the MG and the PMG can be optimised separately. The optimised results show that a torque density in excess of 100kNm/m3 could be achieved, which is significantly higher than any of known electrical machines. However, owing to excessive losses in the mechanical support structures, the prototype exhibited lower torque density and poor efficiency. The design related aspects and issues are analysed and discussed in detail in an attempt to outline problem areas in the design process. Relevant recommendations are also given for future design improvements. The costs of magnetic material accounts for over fifty percent of the total cost of the prototype. Therefore to make the manufacturing of the MGAFG more economically viable magnetic material should be minimised in the design process. / AFRIKAANSE OPSOMMING: In hierdie tesis word die eerste magnetiese geratte aksiale vloed permanente magneet generator (MGAVG) ontwerp, vervaardig en eksperimenteel geëvalueer. In magnetiese ratte (MR) is daar geen kontak tussen werkende dele nie, daarom word geen smeermiddels benodig nie. Dit dra by tot die betroubaarheid van die ratkaste in wind energie generators en kan onderhoud grotendeels uitskakel. Die komplekse struktuur van magnetiese ratte kan egter die betroubaarheid van die ontwerp juis verswak. Daarom moet die meganiese uitleg noukeurig beplan word sodat dit nie die elektromagnetiese werking ondermyn nie. Die magnetiese rat (MR) en die permanente magneet generator (PMG) van die masjien kan magneties of sonder magnetiese koppeling verbind word. In die gekoppelde konfigurasie dra all die permanente magnete van die MR gesamentlik by tot die totale vloed-koppeling in die PMG. Wat die magnetiese gekoppelde konfigurasie meer doeltrefend maak. Minder tyd word benodig om die nie magnetiese gekoppelde konfigurasie te optimaliseer omdat die MR en die PMG apart geoptimaliseer kan word. Die optimale resultate toon dat ’n wringkrag van meer as 100kNm/3 bereik kan word, wat aansienlik beter is as die van bekende elektriese masjiene. Maar as gevolg van oormatige verliese in die meganiese strukture, toon die prototipe lae wringkrag digtheid en swak doeltreffendheid. Die ontwerp probleme word ontleed en bespreek in ’n poging om probleem areas in die ontwerp te identifiseer. Relevante aanbevelings word gegee vir toekomstige ontwerp verbeterings. Die koste van die magnetiese material verteenwoordig meer as vyftig persent van die vervaardigings koste van die prototipe. Koste kan bespaar word op die vervaardiging van die MGAVG deur die hoeveelheid magnete wat gebruik word te beperk.

Thesis (MScEng)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: The electromagnetic and mechanical design aspects of an optimally designed double-sided rotor radial flux permanent magnet wind generator with non-overlap iron-cored stator windings are analysed in this thesis. The generator topology proposed in this study aims to reduce the strength demand on the generator structural support, caused by the magnetic attraction forces between the rotor and stator iron components, and in so doing reducing the overall generator mass. The proposed design has very good cooling properties. Compared to a conventional iron-cored permanent magnet generator and an air-cored permanent magnet generator, the double-sided rotor iron-cored topology performs the best with reference to mass and efficiency. / AFRIKAANSE OPSOMMING: Die elektro-magnetiese en meganiese ontwerp-aspekte van ‘n optimal ontwerpte tweesydige rotor radial-vloed permanente magneet windgenerator met nie-oorvleulende ysterkern statorwindings word in hierdie tesis ontleed. Met die generator topologie wat in hierdie studie voorgestel word, word beoog om die strukturele materiaal wat vir die generator benodig is te verminder. Die magnetise aantrekkingskragte tussen die yster komponente van die rotor en stator word dus aangespreek in hierdie studie, om sodoende ook die algehele massa van die permanente magneet generator te verminder. Die voorgestelde tweesydige-rotor ontwerp het baie goeie verkoelings eienskappe en het ‘n kleiner massa en hoër effektiwiteit as beide ‘n konvensionele ysterkern generator met ‘n enkelsydige-rotor en ‘n tweesydige-rotor lugkern permanente magneet generator met dieselfde drywingsvermoë.

published_or_final_version / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy

No description available.

Permanent magnet synchronous motors are finding ever increasing use in hybrid and electric vehicles. This thesis develops a new control strategy for Permanent Magnet Synchronous Motors (PMSMs) to reduce the motor and inverter losses compared to conventional control techniques. The strategy utilises three common control modes for PMSMs; brushless DC with 120°E conduction, brushless DC with 180°E conduction, and brushless AC control. The torque and power output for each control mode is determined for an example motor system using a three phase axial flux YASA motor and an IGBT inverter. The loss components for the motor and inverter are also estimated using a combination of analytical and simulation techniques and results are then validated against experimental measurements. Efficiency maps for each control mode have been used to determine an optimal mode utilisation strategy, which minimises the total system losses and maximises the available motor torque output. The proposed control strategy switches between the three control modes without interruption of motor torque to maximise the system efficiency for the instantaneous operating speed and demanded torque output. The benefits of the new strategy are demonstrated using an example vehicle over a simulated drive cycle. This yields a 10% reduction in losses compared to conventional brushless AC control.

Master of Science / Department of Electrical and Computer Engineering / Ruth Douglas Miller / This thesis presents the design of two models for permanent-magnet direct-drive wind turbines. The models are of a 10 kW and a 5 MW wind turbine, which are representative of residential scale and commercial scale turbines respectively. The models include aerodynamic and mechanical simulations through the FAST software, as well as concurrent electrical simulations through the SimPowerSystems toolbox for MATLAB/Simulink. The aim is to provide wind turbine designers and researchers with a comprehensive simulation tool that they can use to design and test many different aspects of a wind turbine. The particular novelty of these models is their high level of detail in electromechanical simulations. For each model, a generator speed controller was designed in a reference frame attached to the generator’s rotor, and was executed with a 3-phase active rectifier using space-vector pulse-width modulation. Also for each model, active and reactive power controllers were designed in a reference frame synchronous with the grid, and were executed with a 3-phase inverter using space-vector pulse-width modulation. Additionally, a blade pitch controller was designed for the 5 MW model. Validation of the models was carried out in the MATLAB/Simulink environment with satisfactory results.

Nous proposons dans ces travaux, une solution aux problèmes de longue date posés par le control sans capteur d’une machine électrique. Cette solution consiste à élaborer un contrôleur asymptotiquement stable qui régule la vitesse du moteur en mesurant uniquement les coordonnées électriques. Nous l’avons appliqué à un moteur synchrone à aimant permanent non saillant, perturbé par un couple de charge constant non connu. Le schéma proposé est un observateur non linéaire d’ordre 4, basé sur le control qui ne dépend pas d’opérations non robustes intrinsèques au système, comme l’intégration de boucle ouverte à un système dynamique et ce schéma peut être facilement intégrée en temps réel. Le contrôleur est facile à commander par l’ajustement du gain qui détermine directement le taux de convergence de la position et de la vitesse et charge le couple d’observateurs. Les simulations et les résultats expérimentaux mettent en évidences les bonnes performances ainsi que la robustesse des paramètres d’incertitudes du schéma que nous proposons. La comparaison par simulation avec un contrôleur sans capteur à champ orienté présenté récemment dans la littérature, a également été effectuée. La thèse se termine par des remarques de conclusion et des propositions de sujet de recherche s’inscrivant dans la continuité de ces travaux. / A solution to the longstanding problem of sensorless control of an electrical machine is provided in this work. That is, the construction of an asymptotically stable controller that regulates the mechanical speed of the motor, measuring only the electrical coordinates. The result is presented for a non-salient permanent magnet synchronous motor perturbed by an unknown constant load torque. The proposed scheme is a fourth order nonlinear observer-based controller that does not rely on-intrinsically nonrobust-operations like open-loop integration of the systems dynamical model nor signal differentiation, and can be easily implemented in real time. The controller is easy to commission, with the tuning gains directly determining the convergence rates of the position, speed and load torque observers. Simulation and experimental results that illustrate the good performance, as well as the robustness to parameter uncertainty, of the scheme are presented. A simulated comparison with a sensorless field-oriented controller, recently proposed in the drives literature, is also carried out. The thesis is closed with some concluding remarks and some potential research topics generated from this work.

O presente trabalho trata do estudo e análise da influência da saturação magnética no torque de uma máquina síncrona com ímã permanente no rotor. A máquina síncrona em es-tudo trata-se de uma máquina cuja forma de onda de força contra eletromotriz é trapezoidal. Inicialmente é feito um estudo sobre os efeitos da saturação magnética nos três principais parâmetros da máquina, indutância de fase, relutância (vista pelo circuito que tem como fonte de fluxo magnético os ímãs permanentes) e a força contra eletromotriz. Em seguida, realiza-se um estudo sobre o torque eletromagnético para a máquina e a importância dos parâmetros estudados, demonstrando a forte dependência da qualidade do torque com estes parâmetros. Com base nos estudos sobre saturação e torque, objetiva-se, portanto, descrever o comportamento de cada um dos parâmetros quando da saturação da máquina e quanto/como cada um deles afeta o torque eletromagnético da máquina. A fim de se estudar cada componente do torque separadamente, avalia-se a máquina por meio do Método da Permeabilidade Fixa. Por fim, faz-se simulações em elementos finitos empregando o método apresentado e os resultados são analisados. / This work deals with the influence of magnetic saturation on torque of permanent mag-net synchronous machine. At first, a study of magnetic saturation is carried out in order to understand its influence on three main machines parameters, phase inductance, magnet re-luctance and back electromotive force. A study describing the electric torque and its compo-nents is carried out. This study explain the importance of each machines parameter on electric torques smoothness and amplitude. In order to investigate and describe each torques com-ponent, a review on Frozen Permeability Method is developed. At last, some simulation by means of finite element method with Frozen Permeability Method are carried out. The results are shown and analyzed.

Este trabalho tem por objetivo estudar e avaliar uma técnica de determinação de posição inicial de rotor em máquinas síncronas de ímã permanente de superfície. A técnica de determinação de posição inicial é baseada na aplicação de pulsos ao motor. É proposto também um algoritmo de ajuste automático desses pulsos de forma a criar um mecanismo genérico de determinação de posição inicial de ângulo de rotor para o tipo de máquina em estudo. Simulações são realizadas de forma a garantir funcionamento correto do algoritmo que foi implementado em código C com matemática de ponto fixo. A implementação foi realizada utilizando-se um microcontrolador comercial de baixo custo que não possui hardware para aritmética de ponto flutuante. Um descritivo detalhado da implementação, do sistema de testes e resultados são apresentados ao longo do texto. / This work aims the study and evaluation of a rotor initial angle estimation technique in surface mounted permanent magnet synchronous machine. The technique of the rotor initial angle estimation is based on pulse injection to the motor. It is also proposed in this work an automatic pulse adjustment algorithm in order to create a generic mechanism to estimate rotor initial angle for the machine type under study. Simulations are performed in order to ensure the proper functionality of the algorithm which was implemented in C code with fixed point mathematics. The implementation was performed using a comercial low cost microcontroller which does not have floating point arithmetic capability. A detailed description of the implementation, test system and results are presented in this text.

Visando analisar o comportamento de um gerador de ímãs permanentes a partir de diferentes pontos de carga aplicada, quantificando a magnetização dos ímãs presentes, desenvolveu-se um protótipo com desenho propício à adaptação para geradores eólicos. Como o objetivo é a obtenção do comportamento da magnetização dos ímãs permanentes com vários pontos de carga acoplada, optou-se pela utilização de ímãs de ferrite, com valor médio da densidade de fluxo magnético remanente (Br) igual a 0,39 T. Desta forma, o valor da carga acoplada não necessita atingir valores elevados para verificação da variação do comportamento da tensão após aplicação de carga, facilitando a avaliação de possível desmagnetização parcial ou total dos ímãs instalados. Adicionalmente é estudada divisão de carga do gerador, com tensão de saída retificada, operando em paralelo com um barramento C.C. ou banco de baterias. É apresentada uma abordagem analítica de estudo da desmagnetização dos ímãs permanentes do gerador, bem como um levantamento experimental do mesmo. Conduta semelhante é adotada no estudo da divisão de carga. / Aiming to analyze the performance of a permanent magnet generator, operating under variable load and quantifying the corresponding condition of its magnets, we have developed a prototype adaptable to wind generators. As one of the purposes of this work is to study the magnetic performance of the permanent magnets in several points of load, we have chosen ferrite magnets with average remanence (Br) of 0.39 T. Thus, even light variations in load are enough to verify the variation of the generated voltage, which eases the rating of total or partial demagnetization of the installed magnets. Additionally, we study load share of that generator, with rectified output, operating in parallel with D.C. bus or battery bank. An analytic approach of demagnetization of the generator\'s permanent magnets is also presented, as well as an experimental survey of it. A similar procedure is adopted in the study of the load share.