Dissertations / Theses on the topic 'Fractional Slot'

Today, high efficiency and high torque density electrical machines are a growing research interest and machines that contain no permanent magnet material are increasingly sought. Despite the lack of interest over the last twenty years, the permanent magnet-free synchronous reluctance machine is undergoing a revival and has become a research focus due to its magnet-free construction, high efficiency and robustness. They are now considered a potential future technology for future industrial variable speed drive applications and even electric vehicles. This thesis presents for the first time a synchronous reluctance motor with fractional slot-concentrated windings, utilizing non-overlapping single tooth wound coils, for high efficiency and high torque density permanent magnet-free electric drives. It presents all stages of the design and validation process from the initial concept stage through the design of such a machine, to the test and validation of a constructed prototype motor. The prototype machine utilizes a segmented stator core back iron arrangement for ease of winding and facilitating high slot fill factors. The conventional synchronous reluctance motor topology utilizes distributed winding systems with a large number of stator slots, presenting some limitations and challenges when considering high efficiency, high torque density electrical machines with low cost. This thesis aims to present an advancement in synchronous reluctance technology by identifying limitations and improving the design of synchronous reluctance motors through development of a novel machine topology. With the presented novel fractional slot concentrated winding machine design, additional challenges such as high torque ripple and low power factor arise, they are explored and analysed - the design modified to minimise any unwanted parasitic effects. The electrical and electromagnetic characteristics of the developed machine are also explored and compared with that of a conventional machine. A novel FEA post-processing technique is developed to analyse individual air-gap field harmonic torque contributions and the machines dq theory also modified in order to account for additional effects. The developed machine is found to be lower cost, lower mass and higher efficiency than an equivalent induction or conventional synchronous reluctance motor, but does suffer higher torque ripples and lower power factor. The prototype is validated using static and dynamic testing with the results showing a good match with finite element predictions. The work contained within this thesis can be considered as a first step to developing commercial technology based on the concept for variable speed drive applications.

The permanent magnet synchronous machines with fractional slot and concentrated winding configuration have been steadily gaining traction in various applications in recent times. This is mainly driven by several advantages offered by this configuration such as high-torque density, outstanding efficiency, and easy and low-cost fabrication. The main focus of this thesis is dedicated to the investigation of three main topologies of fractional-slot and concentratedwinding permanent magnet synchronous machines specifically suited for particular applications. Additionally, the cogging torque and torque ripple reduction technique based on a novel axial pole pairing scheme in two different radial-flux permanent magnet synchronous machines with fractional-slot and concentratedwinding configuration are investigated. First, an axial flux permanent magnet segmented-armature-torus machine with laminated stator is proposed for in-wheel direct drive application. Both simplified analytical method and three-dimensional finite element analysis model accounting for anisotropic property of lamination are developed to analyze the machine performance. The predicted and experimental results are in good agreement and indicate that the proposed machine could deliver exciting and excellent performance. The impact of magnet segmentation on magnet eddy current losses in the prototype is carried out by the proposed three-dimensional finite element analysis model. The results show that the eddy current losses in the magnet could be effectively reduced by either circumferentially or radially segmenting the magnets. Furthermore, a magnet shaping scheme is employed and investigated to reduce the cogging torque and torque ripple of the prototype. This is validated using the three-dimensional finite element analysis model as well. Second, a coreless axial flux permanent magnet machine with circular magnets and coils is proposed as a generator for man-portable power platform. Approximate analytical and three-dimensional finite element analysis models are developed to analyze and optimize the electromagnetic performance of the machine. Comprehensive mechanical stress analysis has been carried out by threedimensional structural finite element analysis, which would ensure the rotor integrity at expected high rotational speed. The results from both three-dimensional finite element analysis and experiments have validated that the proposed prototype is a compact and efficient high speed generator with very simple and robust structure. Additionally, this structure offers simplified assembly and manufacturing processes utilizing off-the-shelf magnets. Third, a novel radial flux outer rotor permanent magnet flux switching machine is proposed for urban electric vehicle propulsion. Initial design based on the analytical sizing equations would lead to severe saturation and excessive magnet volumes in the machine and subsequently poor efficiency. An improved design is accomplished by optimizing the geometric parameters, which can significantly improve the machine efficiency and effectively reduce the overall magnet volumes. Magnet segmentations can be employed to further improve the machine performance. Finally, a novel axial pole pairing technique is proposed to reduce the cogging torque and torque ripple in radial flux fractional-slot and concentrated-winding permanent magnet synchronous machines. The implementation of the technique in outer rotor surface mounted permanent magnet synchronous machine shows that the cogging torque and torque ripple can be reduced very effectively with different magnet pairs. However, careful pair selection is of particular importance for compromise between cogging torque and torque ripple minimizations during the machine design stage. This technique is also employed to minimize the cogging torque in a permanent magnet flux switching integrated-stator-generator and it is compared with rotor step skewed technique. The estimated and experimental results show that the axial pole pairing technique can not mitigate the torque ripple of the machine as effectively as rotor step skewed approach although both the techniques could reduce the cogging torque to the same level.

To tackle the issues concerning the global warming and the international energy security, the only way forward is the wide spread adoption of plug-in electric vehicles (EV) in the transportation industry. High power dense and highly efficient electrical machines pave the way for the swift realization of EV. The research underpinned in this thesis describes the new winding configurations and associated slot-pole combinations for permanent magnet (PM) brushless machines that lead to improved performance and facilitate cost reduction. The current state-of-the-art machine technologies and their topologies are weighed against one another qualitatively through a comprehensive literature survey, and quantitatively by a preliminary design study of the most competitive machine technologies for a micro-sized EV application. Compared to the current state-of-the-art, the salient feature of the proposed winding designs is elimination and/or reduction of undesirable space harmonics which result from the existing fractional-slot per pole per phase PM machines with concentrated windings. This brings the benefits of significant reduction of the eddy current loss in the rotor permanent magnets, shorter end-windings and hence reduced copper loss and copper usage, increased power/torque density, reduction in manufacturing cost, and improved energy efficiency. In order to improve power drivetrain availability for EV applications, the thesis proposes the design of 6-phase PM machine as two independent 3-phase systems using the proposed winding configuration. A number of possible phase shifts between two sets of 3-phase windings due to their slot-pole combination and winding configuration are investigated and the optimum phase shift is selected by analysing the harmonic distributions and their effect on machine performance including the eddy current loss in the magnets. The proposed 6-phase winding configuration is applied to the design of an interior permanent magnet (IPM) machine for segment-A EV, under the electrical, thermal, and volumetric constraints, and demonstrated by a series of preliminary functional tests on the prototype machines. The design study and the measurement results show that the proposed winding configuration results into high torque/power dense PM machine with high efficiency over wide operating range. The important design aspects of the new machine topologies for EV application are investigated in detail, which include effect of phase shifts on magnet eddy current loss and unbalanced magnetic pull of the machine, demagnetization assessment of the new machine topology under various fault conditions, and thermal analyses over the driving cycles.

The study on the driving cycle and powertrain of electric vehicle presents the conclusion that there is a regular working area on efficiency map where electric motor works for the most time. Thus, two motivations are proposed: first, to evaluate the efficiency map of electric motor analytically, second, to design an electric motor whose maximum efficiency area on efficiency map covers its regular working area. To evaluate motor efficiency map, three tasks have to be completed: calculating torque-speed characteristic, calculating losses, studying on motor control strategy. For in-wheel application, surface-mounted permanent magnet motor with fractional-slot concentrated-windings is adopted. Its torque-speed profile of flux-weakening control is calculated. Different methods of losses calculation are compared and the results are presented. Motor control strategy is studied to obtain the input electric parameters of other operating points within the torque-speed profile. To design the motor, driving cycle and powertrain of electric vehicle are analyzed. Multi-objective optimization is utilized to obtain the optimal motor design. Different factors impacting motor efficiency map are discussed. The motor designs are compared to illustrate the loss balance of electric motor. Motor design and analytic results are validated in powertrain calculation and finite element calculation. Flux-weakening control is implemented. The co-simulation model is built up for further study to calculate the dynamic efficiency of driving cycle. A prototype with similar typology and winding layout is manufactured. Some preliminary experiment results are presented and compared with analytic results.

This thesis investigates the electromagnetic performance of the fractional-slot interior permanent magnet (IPM) and salient-pole synchronous reluctance (SynR) brushless AC machines having non-overlapping concentrated windings, the SynR machines being excited by bipolar AC sinusoidal currents with and without DC bias. The analyses are validated by finite element calculations and measurements. The PM machines with modular stators are often employed to improve the electromagnetic performance and ease the manufacture process, particularly stator winding. The influence of uniform and non-uniform additional gaps between the stator teeth and back-iron segments on the electromagnetic performance of fractional-slot IPM machines having either un-skewed or step-skewed rotors and different slot openings, viz. open slot, closed slot and hybrid slot (sandwiched open and closed slots), is investigated. The influence of load conditions on cogging torque and back-emf waveforms and the effectiveness of rotor skew on the minimization of the cogging torque, thus the torque ripple, are also examined. It is found that the additional gaps have a negligible influence on the average output torque, but significantly increase the cogging torque magnitude, while their non-uniformity can cause a large increase in both the peak and periodicity of cogging torque waveform, which in turn makes the skew method ineffective. The magnetic cross-coupling level and the sensitivity of cogging torque to manufacturing limitations and tolerances strongly depend on the slot opening materials. The cogging torque magnitude is significantly increased by load, while its periodicity also changes with load which makes the rotor skew less effective unless the machine is skewed by one cogging torque period on load. The electromagnetic performance of the SynR machines under AC sinusoidal bipolar excitation with and without DC bias is investigated and compared for three different winding connections, such as asymmetric, symmetric and hybrid. In general, the SynR brushless AC machines with DC bias excitation exhibit significantly higher torque density than those without DC bias. Comparing with the asymmetric and symmetric winding connections, their hybrid counterpart results in significantly larger mutual inductance variations. Consequently, it results in significantly larger output torque, since such torque is produced by the variation of both the self and mutual inductances. In terms of torque ripple, the symmetric winding connection leads to the best performance. On the other hand, at significantly larger current densities, the hybrid winding connection become more suitable, since it exhibits large average output torque and relatively low torque ripple.

The field of fault-tolerant applications is surely among the most exciting and potentially innovative modern research of the electrical motor where the design is freedom and new solution can be explored. The cost of the permanent magnets and the drives allow to develop new solution, in particular surface mounted permanent magnet machine with fractional-slot winding and reluctance motor assisted from the permanent magnet. The reliability of these machines allows to apply these motors into critical applications where the electrical or mechanical redundancy are required. As regard this argument the literature compare the performance of different solution. In this thesis I have applied a different approach, in particular a mathematical model is combined with the finite element method. This approach allows to use the Fexibility of the analytical model and the precision of the finite element method. The larger part of my research activity has regarded the motors with fractiona-slot winding and the multi-phase machines. The final part of my thesis tells the activity developed during the period spent in ABB Corporate Research Sweden. The aim of my research was to design several solution of electric generators for wave energy, in particular the aim was to design the optimal system that is a compromise among the different component: generator, mechanical converter, inverter, etc..

Synchronous reluctance (SyR) and Permanent magnet Synchronous Reluctance (PM-SyR) machines represent an answer to the growing emphasis on higher efficiency, higher torque density and overload capability of ac machines for variable-speed applications. Their high performance is particularly attractive in electric traction and industry applications. The SyR technology represents a convenient solution to obtain high efficiency machines at reduced cost and high reliability. The manufacturing costs are comparable to other existing technologies such as induction motors. Different SyR and PM-SyR machines with different ratings and applications were designed, for comparison with induction motors having equal frame. An accurate comparison between Induction motors, SyR and PM-SyR machines is reported, with reference to the IE4 and IE5 efficiency specifications that could become mandatory in the next years. Three studies are classified under the term ”Non-Conventional” machines: Line-Start SyR motor: is a special SyR machine designed for constant speed applications, line supplied. The rotor flux barriers are filled with aluminum, to obtain a squirrel cage that resembles the one of an induction motor. The manufacturing costs are comparable to those of the induction motor, and the efficiency is higher. Two prototypes were realized and tested. FSW-SyR: tooth-wound coils and fractional slot per pole combinations were investigated. They are of interest because they permit a simplification and higher degree of automatization of the manufacturing process. However, FSW-SyR machines are known for their high torque ripple, low specific torque and power factor. The number of slots per pole was optimized to maximize the torque density. Dealing with the torque ripple, a lumped parameters model was used together with optimization in SyRE. A design with minimized ripple was obtained, comparable to a distributed winding machine in this respect. This design was prototyped and tested. Mild Overlapped SyR: this study shows a new winding configuration applied to SyR and PM-SyR machines. The proposed case is in the direction to find a hybrid solution between distributed winding and tooth winding motors, that permits to reduce costs and improve performances. One limitation of this solution is that only number of pole pairs equal to five or higher are feasible, and this reduces the applicability of the solution to classical industry applications, where one to three pole pairs are normally used.

Technological advances in the aerospace industry have improved aircraft efficiency and reduced the cost of air transport, leading since 1960 to a continuous growth of the worldwide air traffic. Today it is postulated that also into the foreseeable future both the passenger and cargo air traffic will continue to growth, increasing the CO2 air transport emissions. In this contest, there are many environmental as well as commercial pressures on aircraft manufacturers to improve performances of future aircraft in terms of safety, air pollution, noise and climate change. To achieve these goals, it is necessary revisiting the whole aircraft architecture system, with the introduction of new technologies for performing key functions on aircraft. Today the conventional civil aircraft are characterized by four different secondary power distribution systems: mechanical, hydraulic, pneumatic and electrical. This implies a complex power distribution nets aboard, and the necessity of an appropriate redundancy of each of them. In order to reduce this complexity, with the aim to improve efficiency and reliability, the aerospace designer community trend is towards the `More Electric Aircraft (MEA)' concept, that is the wider adoption of electrical systems in preference to the others. This solution involves an increase of the aircraft electrical loads and, as a consequence, heavy implications for the on-board electrical generation systems are predictable. The resulting increase of the electrical power requirements encourage the research of alternative solutions rather than simply scaling up existing technologies such as generators driven by gearboxes. To address these challenges, many studies are in the direction of the so called `More Electric Engine (MEE)', in which the electrical machines are integrated inside the main gas turbine engine to generate electrical power, start the engine and guarantee safety generation in case of a critical on-flight failure. In this way the mechanical gearbox which connects the actual generators to the aeroengine shaft can be eliminated. The MEA and the MEE concept can be considered as an evolutionary implementation of the `All Electric Aircraft (AEA)', in which all the aircraft on-board systems are supplied in an electrical form. The MEE concept will involve important mechanical and thermodynamic implications in the aeroengine design, making necessary a preliminary system analysis on today conventional aeroengine, in order to evaluate the integration feasibility with the actual mechanical and environmental constraints. The electrical machines can be integrated inside the engine in some different positions, either in the front part before the combustion chamber, in particular in the low-pressure or in the high-pressure compressor stages, or in the rear part of the engine, in the tail-cone zone. In the frame of the GREAT2020 (GReen Engine for Air Transport in 2020) project co-founded by Regione Piemonte, aimed to the development of new eco-compatible aircraft engines for the entry into service in 2020, the MEE concept focus is on the evaluation of the most suitable solution between four possible integration positions in the front part of the today conventional two-shaft GEnx turbofan engine. The rotational speeds and the maximum available volumes are respectively imposed by the shaft connection and by the available spaces inside the aeroengine. In the purpose of the MEE concept on which the work presented in this dissertations is based, in order to evaluate the less critical solution between the proposed, a trade-off study conducted on preliminary electromagnetic design has been performed considering both radial and axial flux surface mounted permanent magnet synchronous machines. The comparison of the different solutions have been done on the base of same sizing indexes. Due to the particular application in which the electrical machine integration is involved, in order to evaluate impact on the whole system performance, a wider trade-off study concerning the overall aeroengine system has been done by the aerospace company Avio, partner of the GREAT2020 project. The focus of the work presented in this dissertation, is the development of appropriate tools to perform a preliminary electromagnetic design of radial and axial flux, surface mounted, permanent magnet synchronous machines with three-phase distributed and single-layer fractional-slot non-overlapping concentrated windings. In particular, this latter winding topology has been considered for its specific application for its shorter end-winding connections respect to the distributed layout, and for their high fault tolerant capability due to the electrical and physical separation between the phases which reduces the possibility of a fault propagation. Regarding the radial flux topologies, both inner and outer rotor machine structures have been considered; for the axial flux machines the single-stage (one stator and one rotor) as well as the multi-stage structures, obtained connecting on the same axis more than one single-stage structure, have been considered. The developed general purpose tools are based on simple geometrical approach using conventional design equations. The geometrical dimensions are computed starting from the design specifications and material utilization indexes imposed by the designer. The implemented codes would be a useful tool for the electrical machine designer in order to quickly define a preliminary electromagnetic design starting from a fresh sheet of paper. The conducted comparisons with commercial software have proved the validity of the tools for the conducted MEE trade-off study; however, in a prototype design aimed to the construction, detailed analysis using commercial software available on the market and Finite Element Method analysis have to be done in order to verify and improve in details the preliminary electromagnetic design obtained by the implemented codes.

L'objectif de la thèse est la conception d'une machine électrique dédiée à des applications Mild-Hybrid. En assurant certaines fonctionnalités, cette machine permet de réduire la consommation de carburant dans le véhicule et par conséquent réduire la quantité des gaz rejetés. Les contraintes exigées par un tel domaine à la fois pour le couple et la puissance nous amène à étudier les machines synchrone polyphasée à aimants avec un bobinage concentré autour des dents. Cette technologie de bobinage permet d'obtenir des machines de rendement élevé qui sont faciles à fabriquer, réparer et recycler, mais avec un certain niveau d'effets parasites. Afin de trouver un compromis entre ces effets et la capacité à fournir de couple, la thèse concerne l'étude des topologies de bobinage à pas dentaire avec différentes combinaisons Encoches/Pôles. Un modèle analytique constituant un outil permettant de comparer les pertes d'aimants entre les différentes combinaisons est développé. De nombreuses configurations sont comparées afin de faire le choix le plus adéquat pour minimiser les effets parasites. Les topologies rotoriques qui permettent à la machine de présenter une large plage de vitesse sont examinées, mais en tenant compte également de la nécessité de protéger leurs aimants contre des harmoniques nocifs de FMM. Enfin, l'exploitation du degré de liberté offert par une structure à 5 phases est abordée montrant que, le couple peut être significativement boosté en modifiant la structure de rotor. La cohérence de toutes les études analytiques menées dans la thèse est corroborée par des modèles en éléments finis et des mesures effectuées sur un prototype
The aim of this thesis is to design an electrical machine dedicated for Mild-Hybrid applications. By providing certain functionalities, this machine can reduce fuel consumption in the vehicle and therefore reduce the amount of released gases. The challenges imposed by such application on both torque and power lead us to study the multiphase PM machines with concentrated windings. This windings technology provides efficient machines which are easy to manufacture, repair and recycle, but accompanied with a certain level of parasitic effects. In order to find a compromise between these effects and the ability to provide torque, the thesis concerns the study of winding topologies with different Slots/Poles combinations. An analytical model constituting a tool to compare magnet losses between various combinations is developed. Many configurations are compared in order to make the most appropriate choice which minimizes parasitic effects. The rotor topologies that allow the machine to provide a wide speed range are examined, taking into account their role in magnets protection against MMF harmful harmonics. Finally, the exploitation of freedom degree offered by a 5-phases structure is discussed, showing that the torque can be significantly boosted by modifying the rotor structure. The consistency of all analytical studies presented in the thesis is corroborated by finite element models and a prototype measurement

L’alternateur étudié dans cette thèse équipe une éolienne flottante à axe vertical. Il s’agit d’unemachine synchrone de 2MW, polyphasée, bobinée sur plots, à pas fractionnaire, à aimants et à prisedirecte. L’objectif majeur de la thèse est la caractérisation de cet alternateur afin d’en évaluer lesperformances. Une modélisation analytique de la perméance d'entrefer et de la force magnétomotriceont conduit à l'étude de l'induction d'entrefer dont le contenu harmonique s'est révélé êtreparticulièrement riche. La caractérisation a également porté sur la détermination des inductancespropres et mutuelles, avec un calage du modèle effectué en exploitant des mesures expérimentalesfaites à l’arrêt. La particularité de la machine étudiée nous a amené à considérer un enroulement fictiféquivalent dans le but de déterminer les inductances cycliques, nécessaires à l'établissement du schémamonophasé équivalent. De plus, le fonctionnement back to back de la machine a été étudié et simulé. Ilpermet de faire des tests de la machine elle-même mais aussi des éléments de la chaîne de conversion,sans l'utilisation d'une deuxième machine ou des pâles pour entraîner le rotor du prototype. Il offre enplus la possibilité de tester différents type de fonctionnements et d'évaluer la puissance que peutproduire la machine : différents scénario de fonctionnement ont été simulés et les paramètresnécessaires aux essais sur site ont été définis. Le fonctionnement back to back a fait l’objetd’investigation sur une machine synchrone classique. Les difficultés de fonctionnement ontnotamment pu être mises en évidence avec une modélisation analytique des phénomènesélectromagnétique qui s'y produisent et des essais expérimentaux
The studied alternator equips a vertical axis offshore wind turbine. It is a 2MW fractional slotconcentrated winding permanent magnet synchronous polyphase machine, directly connected to bladeturbine. The principal purpose of this thesis consists in characterizing the alternator in order toevaluate its performances. The air gap permeance and the magnemotive force analytical modelingleads to study the air gap flux density and its harmonic content, which is particularly rich. Thecharacterization has also concerned the self and mutual inductance determination, which has requiredstalling the model by exploiting experimental measurements done at standstill. The particularity of thestudied machine leads us to consider an equivalent fictitious winding in order to determine the cyclicalinductances, necessary for the single-phase equivalent scheme establishment. Moreover, the machineback to back functioning has been studied and simulated. This functioning allows testing the machineitself and the other conversion chain subsystems, without using a second machine or blades to drivethe prototype rotor. It offers the possibility to test different types of operating points and to estimatethe power that can produce the studied machine: different operating points scenarios have beensimulated and parameters for tests have been defined. The back to back functioning of a classicalsynchronous machine has been also investigated, with an analytical modeling of the electromagneticphenomena and experimental tests

Cette thèse est dédiée à la conception optimale de la machine synchrone à rotor bobiné modulaire sans balais pour les systèmes embarqués. Cette machine est basée sur une structure POKIPOKITM développée par Mitsubishi Electric Coopération avec les convertisseurs de puissance intégrée pour augmenter la capacité de tolérance aux défauts. L'analyse électromagnétique est utilisée pour étudier les différentes machines synchrones à rotor bobiné et donc, pour sélectionner la structure qui offre la meilleure tolérance aux défauts et les performances les plus élevées. D’abord, le choix des nombres de phases, d’encoches et de pôles est un point critique. Ensuite, quelques machines sont analysées et comparées selon les critères tels que la densité de couple, le rendement, l'ondulation de couple. La machine avec 7 phases, 7 encoches et 6 pôles est alors choisie. Cette machine est ensuite comparée à la machine synchrone à aimant permanent monté en surface. Le résultat démontre que la machine synchrone à rotor bobiné modulaire sans balais possède le potentiel de remplacer la machine synchrone à aimant permanent dans notre application parce qu’elle présente des performances similaires avec une capacité de tolérance aux défauts élevée. Dans un second temps, une fois la structure 7phases/7encoches/6pôles choisie, cette machine est optimisée en utilisant NOMAD (qui est un logiciel d'optimisation de boîte noire) afin de minimiser le volume externe sous les contraintes électromagnétiques, thermiques et mécaniques. Comme ce problème d'optimisation est extrêmement difficile à résoudre, quelques relaxations ont été effectuées pour tester les différents algorithmes d'optimisation : fmincon (de Matlab) et NOMAD. Nous remarquons que NOMAD est plus efficace que fmincon pour trouver des solutions à ce problème de conception où certaines contraintes sont calculées par des simulations numériques (ANSYS Maxwell ; code éléments finis). En utilisant la méthode NOMAD basée sur l’algorithme Mesh Adaptive Direct Search, nous obtenons des résultats optimaux qui satisfont toutes les contraintes proposées. Il est nécessaire de valider ce design optimisé en vérifiant toutes les contraintes par des simulations électromagnétiques et thermiques en 3D. Les résultats montrent que le couple moyen obtenu par la simulation en 3D est inférieur à la valeur souhaitée. Par conséquent, en augmentant la longueur de la machine, une nouvelle machine corrigée est ainsi obtenue. Nous observons que les pertes de fer obtenues en 3D sont plus élevées qu'en 2D en raison du flux de fuite dans la tête de bobinage. En prenant les valeurs des pertes analysées par la simulation en 3D, la température de surface de la nouvelle machine analysée par la méthode Computational Fluid Dynamics est plus élevée que celle calculée dans l’optimisation. Enfin, un prototype de machine est construit et quelques tests expérimentaux est réalisés. Le résultat montre que la force électromotrice à vide a une forme d'onde similaire par rapport à la prédiction numérique en 3D et la différence de couple statique maximum entre les tests expérimentaux et les simulations par éléments finis en 3D est faible
This thesis is dedicated to the design and the optimization of modular brushless wound rotor synchronous machine for embedded systems. This machine is constructed based on POKIPOKITM structure with integrated drive electronics. Finite element analysis based optimization becomes more popular in the field of electrical machine design because analytical equations are not easily formalized for the machines which have complicate structures. Using electromagnetic analysis to comparatively study different modular brushless wound rotor synchronous machines and therefore, to select the structure which offers the best fault tolerant capability and the highest output performances. Firstly, the fundamental winding factor calculated by using the method based on voltage phasors is considered as a significant criterion in order to select the numbers of phases, stator slots and poles. After that, 2D finite element numerical simulations are carried out for a set of 15 machines to analyze their performances. The simulation results are then compared to find an appropriate machine according to torque density, torque ripple and machine efficiency. The 7phase/7-slot/6-pole machine is chosen and compared with a reference design surfacemounted permanent magnet synchronous machine in order to evaluate the interesting performance features of the wound rotor synchronous machine. In the second design stage, this machine is optimized by using derivative-free optimization. The objective is to minimize external volume under electromagnetic, thermal and mechanical constraints. Given that an accurate finite element analysis for machine performance takes a long time. Moreover, considering that the average torque can be obtained by simulating the model with only four rotor positions instead of one electric period, optimization strategy is proposed to reduce computational time and therefore, obtain a fast convergence ability by defining relaxed problems which enable minimizing the external volume of the machine under only several constraints such as average torque, torque ripple and copper losses. By testing relaxed problems, two different optimization methods (NOMAD and fmincon) are compared in order to select an appropriate method for our optimization problem. Using NOMAD method based on Mesh Adaptive Direct Search, we achieve optimal results which satisfy all of the constraints proposed. In the third design stage, all constraints are validated by 3D electromagnetic and thermal simulations using finite element and computational fluid dynamics methods. The 3D results show that the average torque obtained is lower than the desired value. By increasing the length of the machine, a new corrected machine is thus obtained. It can be observed that the iron losses obtained in 3D are higher than that in 2D due to the leakage flux in the end-winding. Then, the machine temperature is analyzed by using ANSYS Fluent. Note that the surface temperature is higher than that calculated in the optimization and the coil temperature is 8.48°C higher than the desired value (105°C). However, some dissipation by the shaft and the bearings of the machine are expected to reduce the machine temperature. Finally, a machine prototype is built and some experimental tests are carried out. The results show that the electromotive force has a similar waveform compared to 3D prediction and the difference of the measured and predicted maximum static torques is small

O nitrogênio é um dos nutrientes mais importante para o desenvolvimento vegetal e o mais aplicado em diversos cultivos agrícolas. Dentre as fontes nitrogenadas disponíveis, a ureia se destaca pela alta concentração de nitrogênio que remete a diversas vantagens econômicas e operacionais no sistema de produção agrícola. Porém, além da alta propensão a perdas, principalmente por volatilização do gás amônia, tem-se a necessidade do aumento da produtividade de modo ao suprimento da demanda crescente de alimentos, fibras e energia. Considerando estes fatores, uma nova vertente de pesquisa está voltada a aplicação de tecnologias à ureia, os fertilizantes com tecnologia agregada, estes vêm se destacando e disponibilizando alternativas de novos produtos no mercado. Com base no exposto, buscou-se elucidar os seguintes questionamentos: As novas tecnologias aplicadas a ureia possibilitam a redução de perdas por volatilização? As novas tecnologias aplicadas a ureia modificam suas transformações inorgânicas e orgânicas no solo e, em caso de modificação, estas são positivas? O uso de tecnologias aplicadas à ureia reflete em maior longevidade na liberação do nutriente ao solo e, em caso positivo, esta longevidade é vantajosa? A combinação entre produtos de ureia convencional e com tecnologia agregada, pode trazer mais benefícios à cultura do milho do que a aplicação destes isoladamente? A substituição do uso/aplicação da ureia em sua forma tradicional pela ureia com tecnologia agregada, na cultura do milho, é viável economicamente ao produtor? Para responder a estes questionamentos, foram conduzidos três experimentos: análise das frações do nitrogênio provenientes da ureia com inibidores de urease; caracterização da dinâmica de liberação e longevidade de fertilizantes recobertos com polímero e enxofre e; análise da produtividade da cultura do milho submetida a adubação com ureia recoberta com polímero e enxofre. O primeiro experimento permitiu concluir que o uso dos inibidores de urease tem potencial para a redução das perdas por volatilização da amônia, foi possível verificar as transformações sofridas pelo nitrogênio desde a aplicação do grânulo até a disponibilidade das formas minerais, passando a incorporação do nutriente na matéria orgânica. No segundo experimento concluiu-se que os fertilizantes recobertos com polímero e enxofre possuem dinâmica exponencial de liberação, o recobrimento é dependente da temperatura, umidade do solo, tipo de material de recobrimento e processo de recobrimento (espessura), que afetam diretamente a liberação e longevidade destes fertilizantes. O último experimento mostrou que uso dos fertilizantes recobertos com polímero e enxofre aumenta a produtividade, os parâmetros biométricos, os parâmetros nutricionais e a qualidade do grão da cultura do milho. As combinações realizadas entre os produtos recobertos com a ureia convencional são alternativas para o aumento da produtividade resultando em valores superiores a aplicação dos insumos de forma isolada. A combinações de produtos recobertos com a ureia convencional é opção para a redução do investimento e, consequentemente, custo de produção resultante da adoção destas novas tecnologias.
Nitrogen is one of the most important nutrient for plant development and the most applied nutrient in several agricultural crops. Among the available nitrogen sources, urea differ due to the high concentration of nitrogen that result to several economic and operational advantages in the agricultural production system. However, in addition to the high propensity for losses, mainly due to the ammonia volatilization, the need to increase yield in order to supply the growing demand for food, fiber and energy emerge. Considering these factors, a new research area is focused to aggregate technologies to the urea, they call fertilizers with aggregate technology, this type of fertilizers emerges and brings new alternatives about new products available in the market. Based on the above, it was tried to answer the following questions: Does the new technologies applied to urea fertilizer enable the reduction of losses by volatilization? The new technologies applied to urea modify their inorganic and organic transformations in the soil and, if modified, are these positive? Does the use of technologies applied to urea reflect in a longer longevity in the release of the nutrient to the soil and, if so, is this longevity advantageous? Can the combination of conventional urea and aggregate technology products brings more benefits to cons than the application of these alone? Is the substitution of urea in its traditional form by urea with aggregate technology in the maize crop economically viable to the producer? In order to answer these questions, three experiments were conducted: analysis of nitrogen fractions from urea and urea mixed with inhibitors; Dynamics of release and longevity of polymer sulfurcoated fertilizers; Analysis of maize yield submitted to fertilization with polymer and sulfur coated urea. The first experiment allowed concluding that the use of the urea inhibitors has potential to reduce losses by ammonia volatilization, it was possible to verify all the changes undergone by the nitrogen fertilization since the granule until the availability of the mineral forms, including the immobilization of the nutrient in organic matter. In the second experiment, it was concluded that the polymer and sulfur coated fertilizers have exponential dynamics of release, the coating depends on the temperature, soil moisture, type of coating material and coating process (thickness), which directly affects the release and longevity of these fertilizers. The last experiment showed that the use of the coated fertilizers with polymer and sulfur increases the yield, the biometric parameters, the leaf concentration and the quality of grain to the maize crop. The combinations performed between the coated products with conventional urea are alternatives for increasing the yield resulting in higher application values of the inputs in an isolated way. Combinations of coated products with conventional urea is an alternative to reduce investment and consequently the production costs, it will result the adoption of these new technologies.

Les machines asynchrones (MAS) à cage d’écureuil sont des machines électriques fiables, robustes et à faible coût de fabrication. Pour des raisons historiques et de fiabilité, elles sont principalement dotées de bobinages statoriques distribués. Toutefois, même si ces derniers assurent un fonctionnement très satisfaisant, ils ont des têtes de bobines de longueurs significatives, ce qui engendre des pertes Joule non négligeables. Dernièrement, différents bobinages dentaires avec des têtes de bobines réduites, ont été utilisés dans des machines synchrones avec des performances intéressantes. En plus de réduire les pertes Joule statoriques, ces bobinages permettent de concevoir des machines plus compactes et tolérantes aux défauts. Leur utilisation est moins répandue dans les MAS à cage de par les problèmes induits par les harmoniques spatiaux dans la force magnétomotrice qui en est issue. Les travaux de la thèse ont pour objectif la conciliation de l’utilisation de ces bobinages dans des MAS avec de meilleures performances. Une analyse détaillée est d’abord menée pour appréhender précisément les phénomènes physiques liés à l’utilisation des bobinages dentaires dans les machines asynchrones aussi bien en régime permanent que lors du démarrage. Un modèle analytique paramétrique de machine asynchrone à cage d’écureuil a ensuite été développé. Ce modèle permet de concevoir des bobinages dentaires avec un contenu harmonique spatial maitrisé mais également des rotors avec différents nombres de barres équidistantes ou non. Sur la base de cet outil, des optimisations ont alors été menées tant sur le stator et son bobinage que sur la structure rotorique montrant qu’il est possible d’aboutir à des structures ‘atypiques’ avec des performances satisfaisantes. Enfin, dans une optique de validation, une MAS à bobinage dentaire avec une cage rotorique innovante a été développée et ses performances en termes de couple développé ont été évaluées au travers de simulations numériques et d’essais réalisés sur un prototype
Squirrel cage induction machines (IM) are reliable, robust and low cost manufacturing electrical machines. For historical and reliability reasons, they are mainly equipped with distributed stator windings. However, even if the latter ensure very satisfactory operation, they have significant end-coils lengths, which generate non-negligible Joule losses. Recently, different fractional slot concentrated windings (FSCW) with reduced end-coils have been used in synchronous machines with interesting performances. In addition to reducing stator Joule losses, these windings enable to design machines that are more compact and fault tolerant. Their use is less common in IM due to the problems induced by spatial harmonics in the magneto motive force when supplied. The aim of this work is to find the best way to use FSCW windings in IM while ensuring good performances. A detailed analysis is first carried out to precisely understand the physical phenomena associated with the use of FSCW in induction machines both in steady state and during start-up. A parametric analytical model of a squirrel cage induction machine was then developed. This model enables to design FSCW windings with a controlled spatial harmonic content but also rotors with different numbers of bars that are equidistant or not. On the basis of this tool, optimizations were carried out both on the stator and its winding and on the rotor structure, showing that it is possible to achieve "uncommon" structures with satisfactory performance. Finally, a fractional slot concentrated winding IM with an innovative rotor cage was developed. Its performance in terms of the developed torque was evaluated through numerical simulations and tests carried out on a prototype

Les processus magmatiques qui régissent l'accrétion crustale au niveau des dorsales médio-océaniques à expansion lente restent à l'heure actuelle mal contraints. Parmi les processus potentiellement impliqués dans l'évolution des réservoirs de magma de la croûte inférieure, les réactions associées à des écoulements poreux réactifs au travers de bouillies cristallines - ou mush - tendent à supplanter les processus classiques de cristallisation simple des magmas. La part de ces processus dans la formation des gabbros cumulatifs de base de croûte est dépendante des modes de migration des liquides, qui sont eux-mêmes corrélés à la géométrie des réservoirs considérés. En combinant des études structurales, pétrographiques et géochimiques à haute résolution de sections in situ forées dans un corps complexe océanique de la dorsale Sud-Ouest indienne, j'ai pu apporter de nouvelles contraintes sur les modes de formation et d'évolution des réservoirs magmatiques impliqués lors de l'accrétion crustale. Le modèle de réservoir développé est généralisable, au moins en partie, à d'autres portions de croûte inférieure océanique. Ce modèle, ainsi que les nouvelles contraintes de l'étude expérimentale couplée des processus de cristallisation, ouvre la voie vers de nouvelles quantifications des processus d'interaction liquides-roches dans la différenciation des lithologies gabbroïques, et de manière plus générale dans l'évolution des liquides magmatiques de la croûte océanique. Ces développements vont de pair avec l'évolution au cours des dernières décennies de la vision des systèmes magmatiques crustaux, passant de chambres magmatiques constituées de liquides vers des modèles de réservoirs magmatiques majoritairement constitués de mush cristallins
Magmatic processes that govern crustal accretion at mid-ocean ridges still need to be better constrained. Among the processes potentially involved in the evolution of the lower crust magma reservoirs, reactions associated with reactive porous flow through crystal mushes tend to be considered as one of the predominant processes together with simple crystallization of magmas. The share of these processes during magma differentiation is dependent on the modes of melt migration and is thus correlated to the geometry of the reservoirs considered. By combining high-resolution structural, petrographic and geochemical studies of in situ sections drilled in an oceanic core complex of the Southwest Indian Ridge, I was able to bring new constraints on the formation and evolution of magmatic reservoirs involved in crustal accretion. All or part of the igneous reservoir model developed herein can be applied to other sections of lower oceanic crust. This model, together with additional constraints obtained by the coupled experimental petrology study of crystallization processes, paves the way for new quantifications of the involvement of melt-rock reactions in the differentiation of gabbroic lithologies, and more generally in the evolution of melts within the oceanic crust. Those developments are consistent with the constant evolution in recent decades of the understanding of crustal magmatic systems, which shifted from melt-filled magma chambers to igneous reservoir models mostly composed of crystal mushes

碩士
逢甲大學
電機工程所
97
This paper deals with the design of an interior permanent magnet (IPM) synchronous motor for use in electric power steering system. Such an application requires the motor having small volume, high efficiency and low torque ripple. First, three IPM synchronous motor configurations are analyzed and compared. One of them is chosen based on the performance requirement. Second, to enhance the motor performance and reduce the magnet volume, the Taguchi method coupled with the finite element analysis is performed. Finally, the heat transfer analysis of the motor is also conducted. Results show that the designed fractional-slot IPM synchronous motor meets the specification within the permissible temperature rise.

The permanent magnet synchronous machines with fractional slot and concentrated winding configuration have been steadily gaining traction in various applications in recent times. This is mainly driven by several advantages offered by this configuration such as high-torque density, outstanding efficiency, and easy and low-cost fabrication. The main focus of this thesis is dedicated to the investigation of three main topologies of fractional-slot and concentratedwinding permanent magnet synchronous machines specifically suited for particular applications. Additionally, the cogging torque and torque ripple reduction technique based on a novel axial pole pairing scheme in two different radial-flux permanent magnet synchronous machines with fractional-slot and concentratedwinding configuration are investigated. First, an axial flux permanent magnet segmented-armature-torus machine with laminated stator is proposed for in-wheel direct drive application. Both simplified analytical method and three-dimensional finite element analysis model accounting for anisotropic property of lamination are developed to analyze the machine performance. The predicted and experimental results are in good agreement and indicate that the proposed machine could deliver exciting and excellent performance. The impact of magnet segmentation on magnet eddy current losses in the prototype is carried out by the proposed three-dimensional finite element analysis model. The results show that the eddy current losses in the magnet could be effectively reduced by either circumferentially or radially segmenting the magnets. Furthermore, a magnet shaping scheme is employed and investigated to reduce the cogging torque and torque ripple of the prototype. This is validated using the three-dimensional finite element analysis model as well. Second, a coreless axial flux permanent magnet machine with circular magnets and coils is proposed as a generator for man-portable power platform. Approximate analytical and three-dimensional finite element analysis models are developed to analyze and optimize the electromagnetic performance of the machine. Comprehensive mechanical stress analysis has been carried out by threedimensional structural finite element analysis, which would ensure the rotor integrity at expected high rotational speed. The results from both three-dimensional finite element analysis and experiments have validated that the proposed prototype is a compact and efficient high speed generator with very simple and robust structure. Additionally, this structure offers simplified assembly and manufacturing processes utilizing off-the-shelf magnets. Third, a novel radial flux outer rotor permanent magnet flux switching machine is proposed for urban electric vehicle propulsion. Initial design based on the analytical sizing equations would lead to severe saturation and excessive magnet volumes in the machine and subsequently poor efficiency. An improved design is accomplished by optimizing the geometric parameters, which can significantly improve the machine efficiency and effectively reduce the overall magnet volumes. Magnet segmentations can be employed to further improve the machine performance. Finally, a novel axial pole pairing technique is proposed to reduce the cogging torque and torque ripple in radial flux fractional-slot and concentrated-winding permanent magnet synchronous machines. The implementation of the technique in outer rotor surface mounted permanent magnet synchronous machine shows that the cogging torque and torque ripple can be reduced very effectively with different magnet pairs. However, careful pair selection is of particular importance for compromise between cogging torque and torque ripple minimizations during the machine design stage. This technique is also employed to minimize the cogging torque in a permanent magnet flux switching integrated-stator-generator and it is compared with rotor step skewed technique. The estimated and experimental results show that the axial pole pairing technique can not mitigate the torque ripple of the machine as effectively as rotor step skewed approach although both the techniques could reduce the cogging torque to the same level.

碩士
逢甲大學
電機工程學系
104
This thesis describes the design and analysis of a 14-pole/12-slot fractional-slot concentrated winding surface permanent magnet motor for electric vehicle applications to satisfy the torque-speed operating range against the New European Driving Cycle (NEDC) and thermal constraints. The specifications of the motor is three-phase, 5 kW at a rated speed of 1350 rpm. The prototype design of the motor is done with the aid of magnetic circuit design software, SPEED, and electromagnetic field analysis based on finite element method software, Flux2D. Results from this study shows that the machine with single-layer winding has higher performance characteristics and is selected for the following study. A sensitivity analysis, Taguchi method and fuzzy Taguchi method is used to the optimal design of the motor for maximum both efficiency and the torque per unit magnet volume and minimum the torque ripple. Finally, a mechanical and a thermal analysis of the motor are also investigated and discussed in this thesis.

Der Beitrag stellt Zweischicht-Bruchlochwicklungen mit einem Wickelschritt von zwei Nuten als einen m¨oglichen Kompromiss vor, welcher weniger ohmsche Verluste als bei klassischen verteilten Wicklungen und weniger Ummagnetisierungsverluste als bei Zahnspulenwicklungen ermöglicht. Er diskutiert Entwurf und Eigenschaften solcher Wicklungen f¨ur drei- und sechssträngige Synchronmaschinen anhand ausgewählter Beispiele.
This paper presents two layer fractional slot windings with a winding step of two slots as a possible compromise which enables less ohmic loss than classic distributed windings would have and less hysteresis and eddy loss than fractional slot concentrated windings would have. It discusses properties and design of such windings for three- and six-phase synchronous machines based on selected examples.