Dissertations / Theses on the topic 'Permanent Magnet Synchronous Machines (PMSM)'

This dissertation is concerned with the design of permanent magnet synchronous motors (PMSM) to operate at super-high speed with high efficiency. The designed and fabricated PMSM was successfully tested to run upto 210,000 rpm The designed PMSM has 2000 W shaft output power at 200,000 rpm and at the cryogenic temperature of 77 K. The test results showed the motor to have an efficiency reaching above 92%. This achieved efficiency indicated a significant improvement compared to commercial motors with similar ratings. This dissertation first discusses the basic concept of electrical machines. After that, the modeling of PMSM for dynamic simulation is provided. Particular design strategies have to be adopted for super-high speed applications since motor losses assume a key role in the motor drive performance limit. The considerations of the PMSM structure for cryogenic applications are also discussed. It is shown that slotless structure with multi-strand Litz-wire is favorable for super-high speeds and cryogenic applications. The design, simulation, and test of a single-sided axial flux pancake PMSM is presented. The advantages and disadvantages of this kind of structure are discussed, and further improvements are suggested and some have been verified by experiments. The methodologies of designing super high-speed motors are provided in details. Based on these methodologies, a super high-speed radial-flux PMSM was designed and fabricated. The designed PMSM meets our expectation and the tested results agree with the design specifications. 2-D and 3-D modeling of the complicated PMSM structure for the electromagnetic numerical simulations of motor performance and parameters such as phase inductors, core losses, rotor eddy current loss, torque, and induced electromotive force (back-EMF) are also presented in detail in this dissertation. Some mechanical issues such as thermal analysis, bearing pre-load, rotor stress analysis, and rotor dynamics analysis are also discussed. Different control schemes are presented and suitable control schemes for super high- speed PMSM are also discussed in detail.
Ph.D.
Department of Electrical and Computer Engineering
Engineering and Computer Science
Electrical Engineering

When using an intermittent source of energy such as wind power together with a synchronous machine a frequency converter system is needed to decouple the generator from the grid, due to the fluctuations in wind speed resulting in fluctuating electrical frequency. The aim of this master's thesis is to investigate how different types of rectification methods affect permanent magnet synchronous machines of different saliency ratios. A literature study was carried out to review the research within the area and to acquire the necessary knowledge to carry out the work. Two simulation models were created that include a permanent magnet synchronous generator driven by a wind turbine and connected to the grid via a frequency converter, where one model utilizes active rectification and one utilizes passive rectification. The simulation models were verified by carrying out an experiment on a similar setup, which showed that the simulation results coincide well with the results of the experiment. The results of the simulation study were then used to compare the rectification systems as well as investigate the affect that rotor saliency has on the system. It was shown that the active rectification provided a higher efficiency than the passive rectification system, however the saliency of the rotor had little effect on the system

Cette thèse propose deux commandes adaptatives sans capteur basées sur l'approche en mode glissant pour les moteurs synchrones à aimants permanents internes (MSAP). Les stratégies proposées sont composées d'un observateur adaptatif en mode glissant d'ordre élevé (OAMGOE) en boucle fermée avec un contrôle adaptatif basé sur la super torsion, où les gains de contrôle etd'observateur de la stratégie proposée sont paramétrés en termes d'un seul paramètre. Ensuite, le principal avantage de cette stratégie est que les lois adaptables sont faciles à mettre en oeuvre, évitant les surestimations des gains qui augmententle broutage, réduisant le temps de réglage des gains et réduisant les dommages des actionneurs. En outre, une stratégie d'extraction d'erreur d'estimation de position angulaire est proposée. Ensuite, sur la base de ces informations et en utilisant un système virtuel sans paramètre, OAMGOE est conçu pour estimer la position angulaire et la vitesse dans une large plage devitesse, où les variables estimées fournies par cet observateur sont obtenues avec une plus grande précision, malgré les variations des paramètres, atteignant une plus grande robustesse. Ces états estimés sont utilisés dans la commande robuste proposée pour suivre une référence de vitesse souhaitée et une référence de courant d'axe d souhaitée. Une analyse de stabilité du système enboucle fermée est présentée, en utilisant une approche de Lyapunov. De plus, la stratégie proposée est validée tout au long du montageexpérimental et de simulation afin de montrer sonefficacité
This thesis proposes two adaptive sensorless controls based on sliding mode approach for interior permanent magnet synchronous motor(IPMSM). The proposed strategies are composed of an Adaptive High-Order Sliding Mode Observer (AHOSMO) in closed-loop with an Adaptive Super- Twisting Control (ASTWC), where the control and observer gains of the proposed strategy are reparameterized in terms of a single parameter. Then, the main advantage of this strategy is the adaptable laws are easy to implement, avoiding overestimates of gains that increases of chattering, reducing the time to tune the gains, and reducing the damage of the actuators. Furthermore, a strategy for angular position estimation error extraction is proposed. Then, from this information and using a parameter-free virtual system, AHOSMO isdesigned for estimating the angular position and speed in a wide speed range, where the estimated variables provided by this observer are obtained with greater precision, despite the variations of the parameters, achieving greater robustness. These estimated states are used in the proposed robust control to track a desired reference of speed and direct-axis current. A stability analysis of the closedloop system is presented, using a Lyapunov approach. In addition, the proposed strategy is validated throughout experimental and simulationset-up in order to show its effectiveness

In the aviation industry, safety and robustness are the number one priorities, which is why they use well-tested systems such as hydraulic actuators. However, drawbacks such as high weight and maintenance have pushed the industry toward newer, electrical, actuators that are more efficient and lighter. Electrical actuators, on the other hand, have some reliability issues. In particular, short circuits in the stator windings of Permanent-Magnet SynchronousMotors (PMSMs), referred to as Inter-Turn Short Faults (ITSFs), are the dominating faults, and is the focus of this thesis. ITSFs are usually challenging to detect and often do not become noticeable until the fault has propagated, and the motor is on the verge of being destroyed. This thesis investigates the possibility of detecting ITSFs in a PMSM, at an early stage when only one turn is shorted. The method is limited to finding the faults using ML algorithms. Both an experiential PMSM and a simulated model of the experimental PMSM, with the ability to induce an ITSF, were used to collect the data. Several Machine Learning (ML) models were developed, and then trained and tested with the collected data. The results show that four of the tested ML models, being: Random Forest, Gaussian SVM, KNN, and the CNN, all achieve an accuracy exceeding 95%, and that the fault can be found at an early stage in a PMSM with three coils connected in parallel in each phase. The results also show that the ML models are able to identify the ITSF when the simulated data is downsampled to the same frequency as the experimental data. We conclude that the ML models, provided in this study, can be used to detect an ITSF in a simulated PMSM, at an early stage when only one turn is shorted, and that there is great potential for them to detect ITSFs in a physical motor as well.

The need for efficiency, reliability and continuous operation has lead over the years to the development of fault-tolerant electrical drives for various industrial purposes and for transport applications. Permanent-magnet synchronous machines have also been gaining interest due to their high torque-to-mass ratio and high efficiency, which make them a very good candidate to reduce the weight and volume of the equipment.

In this work, a multidisciplinary approach for the design of fault-tolerant permanent-magnet synchronous machine drives is presented.

The drive components are described, including the electrical machine, the IGBT-based two-level inverter, the capacitors, the sensors, the controller, the electrical source and interfaces. A literature review of the failure mechanisms and of the reliability model of most of these components is performed. This allows understanding how to take benefit of the redundancy generally introduced in fault-tolerant systems.

A necessary step towards fault tolerance is the modelling of the electrical drive, both in healthy and faulty operations. A general model of multi-phase machines (with a number of phases equal to or larger than three) and associated converters is proposed. Next, control algorithms for multi-phase machines are derived. The impact of a closed-loop controller upon the occurrence of faults is also examined through simulation analysis and verified by experimental results.

Condition monitoring of electrical machines has expanded these last decades. New techniques relying on various measurements have emerged, which allow a better planning of maintenance operations and an optimization of the uptime of electrical machines. Regarding drives, a number of sensors are inherently present for control and basic protection functions. The utilization of these sensors for advanced condition monitoring is thus particularly interesting since they are available at no cost.

A novel fault detection and isolation scheme based on the available measurements (phase currents, DC-link voltage and mechanical position) is developed and validated experimentally. Change-detection algorithms are used for this purpose. Special attention is paid to sensor faults as well, what avoids diagnosis errors.

Fault-tolerant control can be implemented with passive and active approaches. The former consists in deriving a control scheme that gives acceptable performance for all operating conditions, including faulty conditions. The latter consists in applying dedicated solutions upon the occurrence of faults, i.e. by reconfiguring the control. Both approaches are investigated and implemented.

Finally, design considerations are discussed throughout the thesis. The advantages and drawbacks of various topologies are analyzed, which eventually leads to the design of a five-phase fault-tolerant permanent-magnet synchronous machine.
Doctorat en Sciences de l'ingénieur
info:eu-repo/semantics/nonPublished

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.

During these decades, Permanent Magnet Synchronous Motor (PMSM) has become a vital part of military, industry and civil applications due to the advantages of high power density, high efficiency, high reliability and simple structure, small volume and light weight. Sometimes, multiple PMSMs are used to carry out cooperative functions. For example, the bogie of a locomotive, the flight control surface of an airplane. These PMSMs usually operates at the same speed. To reduce the volume and weight, an idea of sharing the static power conversion devices, which is called Mono-Inverter Multi-PMSM system (MIMPMSM), is raised. Although many researchers have given different controller solutions for the MIMPMSM system, most of them are not clear in the aspects of system stability and efficiency issues. This has become the biggest obstacle to the practical use of MIMPMSM. Oriented with these problems, starting with a MIMPMSM system with 2 motors, in the first step, we have tested some control strategies by an experiment to verify the feasibility and performance of them. In final, based on the experiment data, we have figured that the overconstraint problem exists in some control strategies. Then, an analysis and controller design based on steady-state model of a Mono-Inverter Dual-PMSM (MIDPMSM) system is carried out.By studying the solution existence problem of the steady-state model, we give out the design guideline to the controller structure. Combining the open-loop stability and steady-state solution, the region of controllability and stability is obtained. Lagrange Multiplier is used develop theexpression of efficiency-optimal steady-staterelated to torque and speed. The experiment has shown that the efficiency of the new controller has improved significantly. Meanwhile, we have explored the influence of parameter variation in system stability and efficiency-optimization. The variation will influence the stability region. But its influence can be eliminated by using Master- Slave strategy. On the other hand, in the aspect of efficiency optimization, the simulation results have shown that parameter mismatch, especially the permeant flux, can cause high efficiency loss. In the last step, this controller is also adapted to a MIMPMSM system with more than two motors. The simulation results demonstrate the effectiveness.

Le travail présenté dans cette thèse s’inscrit dans le cadre de différents programmes de recherches sur la modélisation et la conception des machines synchrones à aimants permanents, pour des applications de transports terrestres. En effet, la tendance actuelle, que ce soit dans la traction ferroviaire, ou dans les véhicules électriques et/ou hybrides électriques, est d’utiliser de tels moteurs pour leurs grandes performances massiques et leur bon rendement. Cette tendance est également observable dans les grandes éoliennes à attaque directe. Toutefois, un inconvénient de ces machines est l’existence de pertes pouvant être importantes dans les aimants permanents. Ces pertes sont d’une part à l’origine d’une dégradation du rendement, mais elles peuvent aussi être à l’origine d’échauffements excessifs des aimants, avec des risques de désaimantation d’une part et des risques de décollement d’autre part. Dans ce contexte, l’objectif de notre travail de thèse a été d’établir de nouveaux modèles, plus précis, des pertes par courants de Foucault dans les aimants. Les modèles utilisés actuellement sont généralement des modèles bidimensionnels qui ignorent donc le fait que les courants de Foucault ont une répartition tridimensionnelle dans les aimants. Afin de valider le modèle développé, une maquette expérimentale a été mise en place. Dans un premier temps, le modèle de calcul des pertes par courants induits dans les pièces massives a été validé en utilisant une approche qui combine les résultats expérimentaux et ceux calculés analytiquement et numériquement. Ensuite différentes grandeurs globales et locales issues du modèle analytique ont été comparées aux éléments finis aussi bien en 2D qu'en 3D de même qu'aux mesures expérimentales. Les modèles et méthodes de calcul et de mesures proposés pourront être efficacement utilisés ultérieurement pour estimer les pertes par courants induits dans les aimants permanents de moteurs synchrone à aimants
The work presented in this thesis is part of various research programs on the modeling and design of permanent magnet synchronous machines for land transport applications. Indeed, the current trend, whether in railway traction, or in electric and / or hybrid electric vehicles, is to use such engines for their high mass performance and good efficiency. This trend is also observable in large direct-attack wind turbines. However, one disadvantage of these machines is the existence of significant losses in the permanent magnets. These losses can cause a deterioration in efficiency, and also be the cause of excessive heating of the magnets, with risks of demagnetization and risks of. In this context, the aim of our thesis work was to establish new, more accurate models of eddy current losses in magnets. The models currently used are generally two-dimensional models which therefore ignore the three-dimensional distribution of eddy currents in the magnets. In order to validate the model developed, we set up an experimental test bench. In a first step, the calculation of induced current losses in massive pieces was validated using an approach that combines the experimental results with those calculated analytically and numerically. Then, different global and local quantities from the analytical model were compared to the finite elements in both 2D and 3D as well as experimental measurements. The models and methods of computation and measurements proposed can be effectively used later to estimate eddy current losses in the permanent magnets of synchronous magnet motors

This thesis focuses on the development of a novel Direct Torque Control (DTC) scheme for permanent magnet (PM) synchronous motors (surface and interior types) in the constant torque region with the help of cost-effective hall-effect sensors. This method requires no DC-link sensing, which is a mandatory matter in the conventional DTC drives, therefore it reduces the cost of a conventional DTC of a permanent magnet (PM) synchronous motor and also removes common problems including; resistance change effect, low speed and integration drift. Conventional DTC drives require at least one DC-link voltage sensor (or two on the motor terminals) and two current sensors because of the necessary estimation of position, speed, torque, and stator flux in the stationary reference frame. Unlike the conventional DTC drive, the proposed method uses the rotor reference frame because the rotor position is provided by the three hall-effect sensors and does not require expensive voltage sensors. Moreover, the proposed algorithm takes the acceleration and deceleration of the motor and torque disturbances into account to improve the speed and torque responses. The basic theory of operation for the proposed topology is presented. A mathematical model for the proposed DTC of the PMSM topology is developed. A simulation program written in MATLAB/SIMULINK® is used to verify the basic operation (performance) of the proposed topology. The mathematical model is capable of simulating the steady-state, as well as dynamic response even under heavy load conditions (e.g. transient load torque at ramp up). It is believed that the proposed system offers a reliable and low-cost solution for the emerging market of DTC for PMSM drives. Finally the proposed drive, considering the constant torque region operation, is applied to the agitation part of a laundry washing machine (operating in constant torque region) for speed performance comparison with the current low-cost agitation cycle speed control technique used by washing machine companies around the world.

The thesis presents deals with the design, analysis, test and control of permanent magnetsynchronous motor(PMSM).An analytical model was carried out based on the d-q frame and the equivalent circuit of PMSM, theanalytical model gives an approximation value of the machine parameters and is carried out byequations from the listed references. this phase includes many iteration steps, once the results wereobtained they were compared with the motor specifications and if they don’t match the requiredspecifications the process must be done again until the desired design is obtained.Once the analytical model is obtained a Finite Element Simulation was carried out using FEMMsoftware to validate the design, in the FEM analysis in this phase the machine designed in theanalytical model is analyzed, once the simulation is done the results from both models are comparedand discussed in the results chapter.It’s important to mark that during the design phase some design parameters were affected andlimited by some factor, for example, the air gap length has been magnified due to manufacturinglimits.

The thesis presents deals with the design, analysis, test and control of permanent magnetsynchronous motor(PMSM). An analytical model was carried out based on the d-q frame and the equivalent circuit of PMSM, theanalytical model gives an approximation value of the machine parameters and is carried out byequations from the listed references. this phase includes many iteration steps, once the results wereobtained they were compared with the motor specifications and if they don’t match the requiredspecifications the process must be done again until the desired design is obtained. Once the analytical model is obtained a Finite Element Simulation was carried out using FEMMsoftware to validate the design, in this phase the designed machine in the analytical model isanalyzed and validated, once the simulation is done the results from both models are compared anddiscussed in the results chapter. It’s important to mark that during the design phase some design parameters were affected andlimited by some factors, for example, the air gap length has been magnified due to manufacturinglimits. The manufacturing process and the prototype building have been started once the optimal designwas selected, the manufacturing process was explained and a comparison study was made to selectthe best manufacturing process suitable and available for this thesis.

This master thesis aimed to design a permanent magnet assisted synchronous reluctancemachine (PMaSynRM) rotor for pump applications which were to be implemented inan existing Induction Machine stator. The machine were to be compared with a similarpermanent magnet synchronous machine (PMSM) with similar torque production in termsof cost and performance.This thesis goes through the theory of the Synchronous Reluctance Machine andthe Permanent Magnet assistance. A rotor was designed by utilizing existing design approachesand simulation of performance by use of finite element analysis. A demagnetizationstudy was conducted on the added permanent magnets in order to investigate thefeasiblity of the design.The final design of the PMaSynRM was thereafter compared to the equivalentsurface-mounted PMSM in terms of performance and cost. The performance parameterswas torque production, torque ripple, efficiency and power factor. Due to the lower torquedensity of the PMaSynRM, for equal torque production the PMSM had a 40% shorterlamination stack than the PMaSynRM.The economic evaluation resulted in that when utilizing ferrite magnets in the PMa-SynRM it became slightly cheaper than the PMSM, up to 20%. However, due to the fluctuatingprices of NdFeB magnets, there exist breakpoints below which the PMaSynRM isin fact more expensive than the PMSM or where the price reduction of the PMaSynRMis not worth the extra length of the motor. However, it was shown that the PMaSynRMis very insensitive to magnet price fluctuations and thereby proved to be a more securechoice than the PMSM
Detta examensarbete avsåg att designa en rotor till en permanentmagnetsassisteradsynkron reluktansmaskin (PMaSynRM) för pumpapplikationer, vilken skulle implementeras i en befintlig asynkronmaskin (IM) stator. Maskinen jämfördes ekonomiskt och prestandamässigt med en liknande synkronmaskin med permanentmagneter (PMSM) med jämförbar vridmomentsproduktion.Uppsatsen avhandlar teorin bakom synkrona reluktansmaskiner och konceptet kring permanentmagnetassistans. Rotorn designades genom användandet av befintliga designmetoder och simulering genom finit elementanalys (FEA). En avmagnetiseringsstudie utfördes på de adderade magneterna för att undersöka rimligheten kring designenDen slutgiltiga designen av PMaSynRMen jämfördes därefter mot den jämlika PMSMen i termer om prestanda och kostnad. De undersökta prestandaparameterarna var vridmoment, vridmomentsrippel, verkningsgrad och effektfaktor. Eftersom vridmomentsdensiteten i en PMaSynRM är lägre än hos en PMSM så visade sig PMSMen ha en 40% kortare lamineringskropp än PMaSynRMen vid jämnlik vridmomentsproduktion.Den ekonomiska utvärderingen resulterade i att vid användandet av ferritmagneter i PMaSynRMen så blev den något billigare än PMSMen, upp till 20%. På grund av fluktuerande priser hos NdFeB magneter, så finns det brytpunkter där PMaSynRMen faktiskt blir dyrare än PMSMen eller då kostnadsreduktionen för PMaSynRMen kan bedömas att vara för låg med tanke på den ökade längden och vridmomentsrippel. Däremot visades det att PMaSynRMen är väldigt okänslig för prisvariationer och därför visades vara ettkostnadsmässigt tryggare val än PMSMen

The McTronX research group, at the Potchefstroom campus of the North–West University, has been researching Active Magnetic Bearings (AMBs). A fully suspended, flywheel energy storage system (FESS) has been developed. Due to excessive unbalance on the rotor, the motor drive could not be tested up to its rated speed. In the interim, until the rotor can be balanced and other rotor dynamic effects have been investigated, the group decided that the existing drive control should be improved and tested on a high–speed permanent magnet synchronous motor (PMSM), using normal roller element bearings. In order to test the motor control a second (identical) PMSM, mechanically coupled to the former, operates in generator mode which serves as the torque load. Two different control algorithms, namely V/f and vector control, are designed and implemented on a rapid control prototyping system, i.e. dSPACE®. The V/f control is an open–loop, position sensorless technique, whilst the vector controller makes use of a position sensor. From the design and implementation it became clear that the vector control is more robust, in the sense that it is less sensitive on parameter variations and disturbances. It can start up reliably even under full load conditions. The V/f control is an attractive alternative to the vector control, especially in AMB systems, where it may be difficult to mount the position sensor, has to operate in a hazardous environment not suited to the sensor or could degrade the reliability of the AMB system. The cost of the position sensor is not really a concern compared to the cost of an AMB system. The V/f control is more suited to fan and pump applications, which has a low dynamic requirement. The V/f control has high startup currents and is not recommended for applications requiring a high starting torque or fast acceleration during operation. The inverter, which drives the PMSM, also had to be developed. With regard to the motor control, the effects of inverter non–idealities had to be accounted, especially for the V/f control. The implemented control algorithms were tested up to 20 krpm. Discrepancies between the expected and actual results are discussed. Overall, the controllers performed as desired. Generally, the project goals have been reached satisfactorily.
Thesis (M.Ing. (Computer and Electronic Engineering))--North-West University, Potchefstroom Campus, 2011.

Characteristics of synchronous machines with permanent magnets depend among others on geometric layout of the machine section. Unlike EC motors, where rectangular arrangement of quantities is suitable, these machines require sinusoidal behaviour. Specific forming of individual machine parts is partially derived from this requirement. This thesis deals with design of such machines, including various geometrical modifications of their sections and examination of influence of those modifications. The thesis includes also analytical calculation procedure of machine parameters as well as verification of final characteristics using the finite element method. It results in a combination of various design methods. FEMM, Maxwell RMxprt and Maxwell 2D Transient Analysis programs were used for verification. Individual modifications of machine geometries are applied to machines with concentrated windings with different ratio of number of slots and poles, and differences between machines and results of individual methods are compared.

More electric aircraft is an electrification scheme of aircraft system with high technical feasibility and good economy. It can reduce the weight of aircraft structure, improve maintenance efficiency and reduce fire hazards. However, the electrification of aircraft system will drastically increase the proportion of electrical equipment, the total power demand and the difficulty of fault diagnosis. This paper uses the energy management method to take up the challenge, with focus on fault diagnosis of permanent-magnet synchronous machines (PMSMs), adaptive load shedding and energy efficient aircraft design. A literature review of the concept evolution from all/more-electric aircraft to energy-optimized aircraft is presented. The main issues of the aircraft electrification process are summarized, and followed by an introduction to the current research and methods. The model of the aircraft electrical system is qualitatively and mathematically recalled, including the generator, the battery, the DC motor, the AC motor, and the electric power converter. The accuracy and computation cost of the aircraft model depends on the complexity of the subsystem models that are involved. Therefore, the level of detail that is necessary for a good precision-versus-simulation-time ratio is discussed by taking the electric system of an industrial level hybrid energy quadcoptor UAV as an example. The analysis shows that the bi-directional instruments, i.e. the electric machine, should be modeled in details while other components can be simplified. PMSMs are a group of on-board electric machines with promising future prospects because of high power density and stability. The model of PMSMs is further developed in this work, especially in the inter-turn and phase-to-phase short-circuit conditions. In case of inter-turn short-circuit fault, a winding-function-based and a fault-current-based model are separately developed. The accuracy of both models are verified and compared through experimental results. The fault-current-based modeling method is applied to the phase-to-phase short-circuit fault and experimentally examined and discussed. General condition monitoring methods require the use of a large number of sensors. A fault detection and isolation method that can have low requirement of sensor is recalled and inherited. The description of the fault phase identification index using this method is relatively imprecise, which is not applicable to the inter-turn short-circuit fault. In this work, the analytical expression of the faulty phase identification index is derived based on the fault models. A method to isolate inter-turn and phase-to-phase short-circuit faults is proposed by a combination of the current- and the voltage-signature residuals. This development expands the application scope of the original fault detection and isolation tool and improves its accuracy. The validity of this fault diagnosis method has been verified by experimental results.Load management is developed to guarantee the normal operation of critical loads by shedding some other loads in case of emergency. Generally, binary decisions are made: either something has gone wrong or everything is fine. However, different types of fault influence the working performance of the load and the entire network in different ways. There are multiple states between totally wrong and pure fine, and the load management decision should be adaptive to each state. In this work, fuzzy logic method is used to degrade the load priority according to the instantaneous working state. Combining it with the fault detection and isolation process, a fault-tolerant adaptive load management is achieved. Finally, this work discusses the aircraft design from the energy management point of view, which consists of the energy efficiency analysis and the multidisciplinary energy efficient design of the integrated aircraft system. The first thermodynamic efficiency has been widely used as a common parameter for depicting the energy utilization, i.e. the ratio of output to input power of the system. However, it ignores the irreversible increase of the entropy and cannot reveal the upper limit of the available work of the system.Based on the second thermodynamic law, this work uses the exergy parameters to analyze the energy utilization of a MEA design scheme. Based on the exergy analysis, an energy-efficient aircraft design method is proposed by optimizing the exergy lost of the whole design. The method could provide a global optimization reference for the integrated aircraft design of a MEA.
Doctorat en Sciences de l'ingénieur et technologie
info:eu-repo/semantics/nonPublished

Cette thèse s’intéresse à l’étude d’une structure de moteur électrique à aimants permanents afin de réduire l’utilisation d’aimants à basse de terres rares et qui puisse être utilisée pour des applications industrielles. Il est montré dans la première partie de ce travail de recherche que la machine synchro-réluctante à aimants permanents est une bonne solution potentielle. Une analyse paramétrique est alors réalisée en utilisant une modélisation par éléments finis pour mettre en évidence les particularités de son comportement électromagnétique. Puis, une modélisation analytique multi-physique innovante du système convertisseur-moteur est détaillée dans le but de calculer les performances de ce dernier en un temps raisonnable. Les modèles multi-physiques présentés dans ces travaux concernent l’onduleur et le moteur. Ils intègrent les aspects électromagnétique, électrique, énergétique, thermique, mécanique et technico-économique. Le modèle multi-physique de la machine électrique est validé par comparaison à des résultats d’essais sur un prototype. Le modèle du système qui a été développé est ensuite utilisé dans une procédure de conception par optimisation de systèmes d’entrainements. Pour cela, une démarche d’optimisation originale est présentée pour le dimensionnement conjoint de deux applications en imposant la contrainte d’utiliser la même tôlerie magnétique. Il s’agit d’une part d’une application à vitesse fixe et d’autre part d’une application de type traction électrique. La méthode d’optimisation employée est à évolution différentielle. Les résultats des optimisations réalisées permettent de déterminer des conceptions optimales ou des compromis optimaux aux sens de Pareto qui répondent aux deux applications visées. Finalement, cette thèse a permis de positionner la machine synchro-réluctante à aimants permanents parmi les structures de machines à fort potentiel industriel
This thesis focuses on the study of a structure of permanent magnet electric motor which reduces the amount used of permanent magnets composed of rare earths and which can be used in industrial applications. In the first part of the research work, it is shown that the permanent magnet assisted synchronous reluctance machine is a good alternative. A parametric analyse is realised using a finite element modelling in order to highlight the peculiarities of its electromagnetic behaviour. Then, an innovative multi-physic analytical modelling for the system inverter-motor is detailed in order to evaluate its performances in a reasonable computational time. The multi-physic models presented in this work concern the inverter and motor. They integrate the electromagnetic, electric, energetic, thermal, mechanic, and techno-economic aspects. The multi-physical model of the electric machine is validated by means of tests carried out on a prototype. The model of the system which has been developed is used in a design procedure by optimization of drive systems. For this purpose, an original optimization approach is presented for the simultaneous design of two applications by imposing the constraint of using the same magnetic lamination. On one hand it is an application of fixed speed and on the other hand an application of electric traction. The optimization method used is a type of differential evolution optimization. The results of the optimizations realised determine the optimal designs or the optimal compromise with Pareto front which deal with both applications. Finally, this thesis has placed the permanent magnet assisted synchronous reluctance machine among structures of machines with great industrial potential

La révolution technologique majeure des nouveaux aéronefs repose sur une électrification intensive de nombreux constituants de l'appareil et le fait que la vitesse des génératrices électriques n'est plus fixe mais variable. Cette nouvelle manière de générer la puissance électrique engendre des variations de tension sur les réseaux DC. De plus, pour accroître la compacité des Machines Synchrones à Aimants Permanents (MSAP) à puissance donnée, on augmente autant que possible leur vitesse d'entrainement, en les associant pour certaines applications à des réducteurs mécaniques. La variation du niveau de tension du bus DC alimentant une MSAP haute vitesse implique son dimensionnement afin d'assurer sa contrôlabilité sur toute la plage de vitesse reportant d'importantes contraintes sur l'onduleur de tension. Pour pallier ce problème, une solution consiste à intercaler un convertisseur DC/DC entre le filtre d'entrée et l'onduleur de tension pour maintenir la tension DC d'entrée de l'onduleur à une valeur adaptée au fonctionnement de la MSAP et optimiser son dimensionnement. Cependant, cette solution augmente l'ordre du système, ce qui accroît la complexité de son contrôle, accentuée par les contraintes liées à la nature haute-fréquence des MSAP considérées.Les travaux menés dans cette thèse concernent l'étude, l'optimisation et le contrôle des structures d'alimentation des actionneurs haute vitesse connectés aux réseaux DC avioniques à tension variable. Il en résulte que pour les applications avioniques considérées, ces architectures d'alimentation intégrant un convertisseur DC/DC supplémentaire permettent de réduire sa masse et son volume sans dégrader le rendement global de la chaîne de conversion notamment avec les convertisseurs à source impédante qui permettent de supprimer structurellement les ondulations de courant en entrée du convertisseur. De plus, des stratégies de commande Pulse Amplitude Modulation employées avec des architectures de contrôle non-linéaires (platitude, passivité) permettent d'assurer le contrôle de ces MSAP haute-vitesse tout en assurant leur stabilité sur toute la plage de fonctionnement
The main technological revolution of the new aircrafts is based on intensive electrification of many components of the aircraft. Moreover, the speed of electrical generators is no longer fixed but variable. This new way of generating electrical power generates voltage variations on DC networks. Besides, to increase the compactness of the Permanent Magnet Synchronous Machines (PMSM) at a given power, their mechanical speed is increased as much as possible by combining them with mechanical reducers for certain applications. The variation of the voltage level of the DC bus supplying a high-speed PMSM implies its sizing in order to ensure its controllability over the entire speed range which carries significant stresses on the Voltage Source Inverter (VSI). To solve this problem, one solution consists in adding an extra DC / DC converter between the input filter and the VSI to maintain the inverter input voltage at a value adapted to the operating point of the PMSM and to optimize its dimensioning. However, this solution increases the order of the system, which increases the complexity of its control, accentuated by the constraints related to the high-frequency nature of the PMSMs considered. The work carried out in this thesis concerns the study, the optimization and the control of the power supply architecture of the high-speed actuators connected to variable-voltage avionic DC networks. As a result, for the avionics applications considered, these power supply architectures integrating an additional DC / DC converter make it possible to reduce the mass and the volume of the power supply structure without degrading the overall efficiency of the conversion chain, in particular by using the impedance-source converters which allow to cancel the DC input current ripples. In addition, Pulse Amplitude Modulation (PAM) control strategies used with non-linear control architectures (flatness, passivity) make it possible to control these high-speed PMSMs while ensuring their stability over the entire operating range

As the cost for permanent magnets are decreasing and the quality of the magnets are increasing the Permanent Magnet Synchronous Machine (PMSM) are becoming more popular. The PMSM is superior to induction machines both in torque per kilograms and efficiency. Typical applications for these machines are applications where machine volume or efficiency is important. In order to control a PMSM the rotor position needs to be known. This can be obtained by usage of sensor or by usage of a sensorless control scheme. Sensorless Control schemes typically divide into two categories; schemes that give good controllability from 2-5 Hz and schemes that gives good controllability at all speeds including zero speed. The focus for this thesis is sensorless control schemes with good controllability at low and zero speeds. Sensorless control is a multi physics challenge where the machine, inverter and control scheme are equally important for the quality of the drive system. In order to describe the saliency in the machine a new saliency machine model is developed in this thesis. The model includes yoke saturation, teeth saturation and induced currents in magnets. In injection based sensorless control the high frequency flux distribution in the machine is of great interest. In this thesis the frequency dependency in inductance is estimated in two machines by using injection of test signals in a large frequency range. Based on the measurements and the new saliency model the high frequency flux distribution is estimated and the frequency dependency of the saliency is described. A variety of different sensorless schemes are published over the last two decades. As the publications uses different test criteria it is challenging to determine the characteristics for the different schemes: three different control schemes are evaluated in terms of determining the scheme characteristics. A new scheme based on [1, 7] is presented in this thesis. The new scheme enables integration of transient excitation and position estimation in every switching period. The continuous injection based schemes evaluated in this work is rotating high frequency carrier injection [2,13,39] and pulsating high frequency carrier injection [3,26]. The different schemes sensitivity to the inverter non linearity is modelled and evaluated. A comparison of the three schemes is presented. Surface mounted PMSM typically has a small saliency. The saliency in a surface mounted PMSM can be increased in several ways. The last part of this thesis presents a redesign approach for an axial flux PMSM. Several approaches are evaluated in terms of synergy effects with the machine cost and performance. An approach based on insertion of semi-magnetic slot wedges are realised in a prototype.

When developing three-phase drives for Electric Vehicles (EVs), it is essential to verify the controller design. This will help in understanding how fast and accurately the torque of the motor can be controlled. In order to do this, it is always better to test the controller using the software version of the motor or vehicle drivetrain than using actual hardware as it could lead to component damage when replicating extreme physical behavior. In this thesis, plant modelling of Permanent Magnet Synchronous Machine (PMSM) and vehicle drivetrain in MATLAB/Simulink for Model Based Design (MBD) is presented. MBD is an effective method for controller design that, if adopted can lead to cost savings of 25%-30% and time savings of 35%-40% (according to a global study by Altran Technologies, the chair of software and systems engineering and the chair of Information Management of the University of Technology in Munich) [1]. The PMSM plant models take effects like magnetic saturation, cross- coupling, spatial harmonics and temperature into account. Two PMSM models in d-q frame based on flux and inductance principles were implemented. Flux, torque maps from Finite Element Analysis (FEA) and apparent inductance from datasheets were used as inputs to the flux- and inductance-based models, respectively. The FEA of PMSM was done using COMSOL Multiphysics. The PMSM model results were compared with corresponding FEA simulated results for verification. A comparison of these PMSM models with conventional low fidelity models has also been done to highlight the impact of inclusion of temperature and spatial harmonics. These motor models can be combined with an inverter plant model and a controller can be developed for the complete model. Low frequency oscillations of drivetrain in EVs lead to vibrations which can cause discomfort and torsional stresses. In order to control these oscillations, an active oscillation damping controller can be implemented. For implementation of this control, a three-mass mechanical plant model of drivetrain with an ABS (Anti-lock Braking System) wheel speed sensor has been developed in this thesis. Analysis of the model transfer function to obtain the pole zero maps was performed. This was used to observe and verify presence of low frequency oscillations in the drivetrain. In order to include the effects of ABS wheel speed sensor and CAN communication, a model was developed for the sensor.
Testning av regulatorernas inställningar med hänsyn till snabbhet och noggrannhet i momentreglering är avgörande i trefasiga drivsystem för elektriska fordon. Oftast är det bättre att simulera i stället för att utföra experimentella tester där komponenter kan skadas på grund av fysisk stress. Detta kallas för Model Based Design (MBD). MBD är an effektiv metod för utformningen av styrningen som kan leda till kostnadsbesparingar på 25%-30% och tidsbesparingar på 35%-40% enligt en studie från Altran Technologies i samarbete med Tekniska universitet i München, TUM. Detta examensarbete behandlar en modell för en synkronmaskin med permanentmagneter (PMSM) samt en modell för drivlinan utvecklad i Matlab/Simulink för MBD. PMSMs modellen inkluderar magnetisk mättnad och tvärkoppling, MMF övervågor och temperatur. Två PMSM modeller har utvecklats. Den första baseras på magnetiskt flöde som erhålls från finita element beräkningar i COMSOL Multiphysics medan den andra bygger på induktanser givna från datablad. En jämförelse av dessa PMSM-modeller med konventionella low fidelity-modeller har också gjorts för att illustrera påverkan temperaturberoende och MMF övervågor. Modellerna kan kombineras med en växelriktarmodell för att utveckla en hel styrenhet. Lågfrekventa oscillationer i drivlinan leder till vibrationer som kan orsaka vridspänningar och försämra komforten i elfordonet. En aktiv dämpningsregulator kan implementeras för att kontrollera spänningarna men en mekanisk drivlinemodell med tre massor och en ABS (anti-lock braking system) hastighetssensor behövs. Den mekaniska modellen har implementerats och analyserats även beaktande en modell för en CAN kommunikationskanal. Oscillationer med låg frekvens kunde observeras i modellen.

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

This thesis is focused on the sensorless control of permanent magnet synchronous machine (PMSM) based on high frequency carrier voltage injection for zero and low speed and third harmonic back-EMF for higher speed, respectively. Differing from the conventional high-frequency carrier signal injection based sensorless controls, a new sensorless control strategy is proposed which injects a pulsating high-frequency carrier voltage into α- (or β-) axis of the stationary reference frame as stable as rotating carrier signal injection method and estimates rotor position information from the amplitude-modulated carrier current response as simple as pulsating carrier signal injection method. By injecting a high frequency square waveform carrier voltage, the bandwidth of the rotor position estimation can be significantly improved due to the higher injected frequency and removal of all filters. When the rotor speed is sufficiently high, the back-EMF based sensorless control should be applied. Third harmonic back-EMF is usually applied as reference for sensorless control since it is not sensitive to the machine and controller parameters. To improve the dynamic performance due to insufficient resolution, a speed error compensation strategy based on the continuous signal of third harmonic flux-linkage is proposed. This method also can be extended to improve the robustness and rotor position estimation in flux observer based sensorless control. Furthermore, based on Extended Kalman Filter (EKF), rotor position can be derived without considering speed even with poor quality signals for single and dual three-phase PMSM. Third harmonic back-EMF based sensorless control also has some restrictions. In salient pole machines, the winding inductance varies with the rotor position which will introduce estimation error. With imbalanced machine parameters, the measured triplen harmonic back-EMF will contain certain fundamental components which will deteriorate the rotor position estimation. By compensating the contained fundamental distortion in advance, the steady-state and dynamic performance of single and dual three-phase PMSM can be remarkably improved with high robustness.

Ce travail de recherche s'intéresse à la commande sans capteur mécanique du moteur synchrone à aimants permanents (MSAP) à pôles saillants, particulièrement en basse vitesse, avec détection de la position initiale du rotor. Après une présentation des techniques et approches qui ont initié nos travaux, en terme d'estimation de la vitesse et/ou de la position, nous avons choisi celles qui présentent plus d'intérêt de point de vue stabilité, robustesse, précision et simplicité d'implémentation. La première approche est basée sur le Système Adaptatif avec Modèle de Référence (MRAS). Quant à la deuxième, elle est réalisée autour d'un observateur non-linéaire pour l'estimation de la position et de la vitesse du MSAP à pôles saillants. Les deux techniques d'observation de la vitesse sont associées à une commande par orientation du flux rotorique avec la technique MLI vectorielle. Pour détecter la position initiale du rotor, nous avons utilisé une nouvelle approche qui permet d'estimer cette position avec une incertitude de 5° mécanique. Cette nouvelle approche est basée sur l'application de signaux tests aux bornes des phases statoriques du MSAP. Des résultats de simulation et expérimentaux sont présentés tout au long de ces travaux pour valider les études théoriques de la commande vectorielle sans capteur mécanique du MSAP. Enfin, nous avons étudié et analysé les performances de la commande tolérante aux défauts sans capteur mécanique du MSAP en présence de défaillances de types transistors à l'état-off. Les résultats expérimentaux obtenus avec les deux approches d'estimation de la vitesse en utilisant l'observateur MRAS et un observateur non linéaire ont permis d'améliorer la fiabilité du système de manière à rendre possible la commande vectorielle sans capteur mécanique en mode dégradé (alimentation avec deux bras de l'onduleur). En effet, les résultats de la commande sans capteur mécanique de la MSAP en mode dégradé montrent que l'observateur non linéaire est le mieux adapté pour ce type de fonctionnement car il présente de faible ondulation du couple et de vitesse. A l'aide d'un banc d'essais que nous avons développé au laboratoire LSIS-pôle Ecole Centrale de Marseille (ECM), nous avons pu valider expérimentalement les différentes approches proposées dans ce travail de recherche. Les résultats obtenus montrent l'efficacité des techniques mises en œuvre pour la commande vectorielle sans capteur mécanique du MSAP à pôle saillant en termes de robustesse, stabilité, précision et rapidité.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2016.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 283-285).
Improvement of performance of robots has necessitated technological advances in control algorithms, mechanical structures, and electric machines. Running, legged robots have presented challenges in the area of electric machinery in particular. In addition to the low-speed, high-torque, low-mass requirements on the machines, the act of running results in an unconventional drive cycle that consists of brief periods of high torque followed by long stretches of minimal torque requirement, a performance envelope that is not matched by commercially-available machines. An optimized motor would dissipate the minimum possible power over the given drive cycle, lowering temperatures and potentially reducing required battery mass or extending range. These performance requirements have motivated faster modeling techniques to enable optimization of designs for these unconventional applications. This thesis presents a novel, fast modeling method for permanent magnet synchronous machines consisting of a hybrid model comprising an explicit Maxwell solution and a Flux Tube solution. The Maxwell solution is performed for the rotor and airgap of the machine, where geometries are simple and materials are homogeneous. The stator, with its geometric complexities and non-linear materials, is modeled with a lumped-parameter model based on ux tubes. The two models are then stitched together, forced to be self-consistent with boundary conditions, and allowed to converge. This captures effects such as cogging torque as well as saturation of the core materials. The method is approximately four orders of magnitude faster than a reference finite element program (0.01 s versus 100 s) for the same accuracy. The modeling method is implemented for two topologies of surface-mount permanent-magnet machines, an internal-rotor machine and an external-rotor machine. It is then used to optimize machine design to a given drive cycle, including effects of core loss. A machine is built to demonstrate the validity of the model and optimization method and test results match predictions of instantaneous torque to within 5% at the worst point. Cogging torque is another aspect of performance that is important to machines for robotics and other applications. These pulsations in torque caused by magnet alignment with geometric features in the stator result in undesired vibrations and issues with control. One method, based on skew, for reducing or eliminating cogging torque is explored, and a simple analytical technique to predict the eect of skew is presented. Based on the machine optimized for the Cheetah, two additional machines were built to explore the effects of cogging: a skewed-rotor machine, and a skewed- stator machine. Each demonstrated reduction of a particular cogging harmonic or all of the cogging. The skewed machines reduced cogging by approximately 85%. Novel magnet shapes which further reduce cogging are presented and finite element modeling suggests that they can further reduce cogging by 60% over a straight skew. The design and optimization tools developed herein and described above were used to optimize a motor for the MIT Cheetah Robot. The resulting motor showed nearly an order of magnitude increase in torque density when compared to commercial, off-the-shelf machines (1.3 kg vs 820 g and 10 Nm vs 28 Nm) with simultaneous improvements to efficiency.
by Matthew G. Angle.
Ph. D.

Permanent magnet synchronous machines (PMSMs) provide several advantages compared with induction machine, such as higher power and torque density, and better dynamic response. Among PMSMs, Surface-mounted permanent magnet (SPM) machine has simple rotor configuration and easy control strategy due to its isotropic characteristics. Plenty of publications have illustrated the fundamentals and the design methods of SPM machines. Based on these, this dissertation presents new design methods for SPM machines. Both design methods are comprehensively illustrated. The presented design methods are embedded into a machine design platform available online. One of the new methods is an automatic design procedure using multi objective optimization method, whose principle is to combine multi objective differential evolution (MODE) optimization with finite element analysis (FEA) to obtain the machine with the best trade-off among the targeted objectives, like maximum torque, minimum torque ripple, good flux weakening capability, etc. Two cases are reported by using such automatic design method, one for a SPM machine with concentrated winding (CW-SPM) and the other with distributed windings (DW-SPM), respectively. The CW-SPM machine is designed for traction application. In this case, design equations, magnetic FEA, multi objective optimization, simplified structural and thermal co-design are presented. Torque and power profiles of the designed machine are reported. The losses and efficiency map are also presented. The DW-SPM machine is capable of low cogging torque thanks to the automatic design procedure. Dependent on demagnetization limit and optimal magnet span calculation, the magnet bounds in optimization process are obtained. The cogging torque and maximum torque waveforms of three different machines on Pareto front are shown, which are obtained by MODE optimization and FEA simulations. One optimum machine is selected as the best trade-off machine among PM volume, torque and cogging torque behaviors. Besides the automatic design process, the other design method called parametric design for SPM machines is reported. The parametric design provides a very effective and concise solution for SPM machine design without losing precision on the machine performance calculation. Three steps of parametric design development are reported. For each step, design flowcharts and examples are presented. Firstly, a parametric design plane was established based on rotor split ratio x and per unit magnetic loading b. All the sizing equations, torque and power factor calculation are functions of x and b. An example for designing a CW-SPM for traction application is reported. Later the parametric design plane was modified into the x and l_m⁄g plane, the latter parameter being the magnet-airgap length ratio. The design process of DW-SPM machines using the parametric plane is described. A prototype 一s built and verified the validity of the design process. Then, a general design approach based on accurate steel loading for both DW and CW SPM machines is proposed. By using subdomain model during the design process, the stator sizing equations are improved by considering the only one most loaded slot pitch rather than the entire pole pitch. Five different cases of SPM machines are analyzed to get the precise flux quantities passing through the most loaded teeth in one slot. A comprehensive parametric design flowchart for SPM machines is addressed. By using the parametric method, machine models are built according to each sizing situation. The steel loadings on both each tooth and yoke are measured by FEA and compared with target steel loading B_fe at open load condition, which shows good agreements with analytical cases. Finally, the designs are also tested at the respective rated currents. The presented methods give insightful and effective means in SPM machine design

In recent years, synchronous reluctance (SyR) machine has been receiving an increasing interest, mainly due to the lack of permanent magnets (PMs) in the rotor, the good torque density, structural robustness and the low cost. The main drawbacks of such a machine are the torque ripple and the low power factor. Nevertheless, they can be efficiently improved with a proper optimization of the rotor flux-barriers geometry. This aspect has been deeply studied in the past and still today, it is the subject of study of many authors. The first part of this thesis continues such a mission investigating the design of SyR machine for challenging fields such as high-speed and fault-tolerant. In high-speed applications both mechanical and magnetic design have to be taken into account to maximize the torque density and, at the same time, to ensure the structural integrity against the high centrifugal forces that arise in the rotor parts. The size of the radial iron bridges play a key role in this contest unlike the tangential ones that can be neglected. In fact, from the magnetic point of view, they should be designed as small as possible to limit the flux linkage that passes through them and to increase the rotor magnetic anisotropy as well. On the contrary, to counteract the centrifugal mechanical stresses on the rotor iron parts, the axial cross section of the radial iron bridges have to be designed accurately to avoid plastic rotor deformations or breakages. A simple magnetic analytical model and a more complex reluctance network of the SyR machine that takes into account these two aspects are described in detail and the maximum power limit curve is computed as well. Some finite element optimizations are carried out to provide SyR motor geometries suitable for different speed ranges. A motor performance comparison between a SyR and surface mounted permanent magnet motor for a high-speed application is made providing interesting results in terms of efficiency and total cost. The fault-tolerant capability of the SyR motor is an intrinsic characteristic due to the absence of rotor PMs. In fact, there is no PM back electromotive force and then no short circuit current or braking torque in case of fault. These features make the SyR motor a promising alternative to the PM synchronous machines. A dual three-phase winding is adopted to further increase the fault–tolerance of the motor drive since it represents a cheaper alternative to the fully redundant and multiphase systems and . The main aim of the study is to find an optimal design solution that allow to achieve good performance in terms of torque density, torque ripple, mutual magnetic coupling and unbalanced radial force on the bearings both in nominal and faulty condition. To do that, the effect of different dual-three phase winding arrangements on the faulty performance are firstly analyzed by means of finite element analysis. Based on these results, two finite element based multi-objectives optimizations are carried out on a 36-slot and 48-slot geometries setting the average torque and torque ripple, in healthy and faulty conditions, as costs functions. The most promising design solutions provided by the optimizations are manufactured and their fault-tolerant capability is evaluated experimentally confirming the reliability of the proposed design solutions. The second part of the thesis deals with the development of bonded magnet mixtures to improve the torque density and power factor of SyR machines. In particular, the magnetic mixtures are made with different percentage of neodymium iron boron magnetic powders and binder. Some mixtures are prepared and characterized in laboratory to get the main magnetic properties such as coercive field, remanence flux and the relative magnetic permeability. The performance of a SyR motor, designed and manufactured for the purpose, are evaluated with the different bonded magnets by means of finite element analysis and experimental tests. Good results in terms of torque density and power factor are obtained confirming the bonded magnets suitability for SyR machine improvements. The design and experimental validation of a PM assisted SyR (PMASyR) machine for a low-voltage electric scooter is described in the last part of the thesis. The multi-objective design of such a machine has been deeply investigated in literature. In these works, the average torque, the torque ripple and the constant power speed range are set as cost functions and only the transversal motor geometry is optimized. Furthermore, the number of winding turns and the motor stack length are properly adapted after the optimization to meet the rated Volt-Ampere ratings. However, this is possible only if the number of turns is high enough that, a relatively small modification of the number of turns or stack length, does not involve significant changes on the motor performance. Conversely, if the voltage limit and the maximum target speed yield a very low number of turns any modification of the number of turns or the stack length may involve completely different machine inputs or, more drastically, compromise the feasibility of the drive system. The novelty of the study is to propose a multi-objective PMASyR motor design procedure that (i) evaluates the feasibility of the drive system in overload and flux-weakening condition and (ii) computes the optimization cost functions in the same operating condition to allow easy and direct considerations of the Pareto fronts, without any further computations and checks after the optimization. A prototype of the most promising design solution is manufactured and tested to prove the effectiveness of the procedure.

La révolution technologique majeure des nouveaux aéronefs repose sur une électrification intensive de nombreux constituants de l'appareil et le fait que la vitesse des génératrices électriques n'est plus fixe mais variable. Cette nouvelle manière de générer la puissance électrique engendre des variations de tension sur les réseaux DC. De plus, pour accroître la compacité des Machines Synchrones à Aimants Permanents (MSAP) à puissance donnée, on augmente autant que possible leur vitesse d'entrainement, en les associant pour certaines applications à des réducteurs mécaniques. La variation du niveau de tension du bus DC alimentant une MSAP haute vitesse implique son dimensionnement afin d'assurer sa contrôlabilité sur toute la plage de vitesse reportant d'importantes contraintes sur l'onduleur de tension. Pour pallier ce problème, une solution consiste à intercaler un convertisseur DC/DC entre le filtre d'entrée et l'onduleur de tension pour maintenir la tension DC d'entrée de l'onduleur à une valeur adaptée au fonctionnement de la MSAP et optimiser son dimensionnement. Cependant, cette solution augmente l'ordre du système, ce qui accroît la complexité de son contrôle, accentuée par les contraintes liées à la nature haute-fréquence des MSAP considérées.Les travaux menés dans cette thèse concernent l'étude, l'optimisation et le contrôle des structures d'alimentation des actionneurs haute vitesse connectés aux réseaux DC avioniques à tension variable. Il en résulte que pour les applications avioniques considérées, ces architectures d'alimentation intégrant un convertisseur DC/DC supplémentaire permettent de réduire sa masse et son volume sans dégrader le rendement global de la chaîne de conversion notamment avec les convertisseurs à source impédante qui permettent de supprimer structurellement les ondulations de courant en entrée du convertisseur. De plus, des stratégies de commande Pulse Amplitude Modulation employées avec des architectures de contrôle non-linéaires (platitude, passivité) permettent d'assurer le contrôle de ces MSAP haute-vitesse tout en assurant leur stabilité sur toute la plage de fonctionnement
The main technological revolution of the new aircrafts is based on intensive electrification of many components of the aircraft. Moreover, the speed of electrical generators is no longer fixed but variable. This new way of generating electrical power generates voltage variations on DC networks. Besides, to increase the compactness of the Permanent Magnet Synchronous Machines (PMSM) at a given power, their mechanical speed is increased as much as possible by combining them with mechanical reducers for certain applications. The variation of the voltage level of the DC bus supplying a high-speed PMSM implies its sizing in order to ensure its controllability over the entire speed range which carries significant stresses on the Voltage Source Inverter (VSI). To solve this problem, one solution consists in adding an extra DC / DC converter between the input filter and the VSI to maintain the inverter input voltage at a value adapted to the operating point of the PMSM and to optimize its dimensioning. However, this solution increases the order of the system, which increases the complexity of its control, accentuated by the constraints related to the high-frequency nature of the PMSMs considered. The work carried out in this thesis concerns the study, the optimization and the control of the power supply architecture of the high-speed actuators connected to variable-voltage avionic DC networks. As a result, for the avionics applications considered, these power supply architectures integrating an additional DC / DC converter make it possible to reduce the mass and the volume of the power supply structure without degrading the overall efficiency of the conversion chain, in particular by using the impedance-source converters which allow to cancel the DC input current ripples. In addition, Pulse Amplitude Modulation (PAM) control strategies used with non-linear control architectures (flatness, passivity) make it possible to control these high-speed PMSMs while ensuring their stability over the entire operating range

Variable speed motor drives are being rapidly deployed for a vast range of applications in order to increase efficiency and to allow for a higher level of control over the system. One of the important areas within the field of variable speed motor drives is the system's operational boundary. Presently, the operational boundaries of variable speed motor drives are set based on the operational boundaries of single speed motors, i.e. by limiting current and power to rated values. This results in under-utilization of the system, and places the motor at risk of excessive power losses. The constant power loss (CPL) concept is introduced in this dissertation as the correct basis for setting and analyzing the operational boundary of variable speed motor drives. The control and dynamics of the permanent magnet synchronous motor (PMSM) drive operating with CPL are proposed and analyzed. An innovative implementation scheme of the proposed method is developed. It is shown that application of the CPL control system to existing systems results in faster dynamics and higher utilization of the system. The performance of a motor drive with different control strategies is analyzed and compared based on the CPL concept. Such knowledge allows for choosing the control strategy that optimizes a motor drive for a particular application. Derivations for maximum speed, maximum current requirements, maximum torque and other performance indices, are presented based on the CPL concept. High performance drives require linearity in torque control for the full range of operating speed. An analysis of concurrent flux weakening and linear torque control for PMSM is presented, and implementation strategies are developed for this purpose. Implementation strategies that compensate for the variation of machine parameters are also introduced. A new normalization technique is introduced that significantly simplifies the analysis and simulation of a PMSM drive's performance. The concepts presented in this dissertation can be applied to all other types of machines used in high performance applications. Experimental work in support of the key claims of this dissertation is provided.
Ph. D.

In this dissertation harmonic current, harmonic torque originated at the load and harmonic torque originated at the motor, where modeled and treated via closed loop control. The dissertation propose a remedy for cancelling harmonic current by placing the proposed adaptive feedforward controller (AFC) in parallel with the FOC current control. Similarly, harmonic torque load was cancelled by proposing an AFC in parallel with the speed control loop. Harmonic torque originated in the motor mainly due to harmonic flux where cancelled through the estimation of harmonic flux, which was achieved by a novel Minimal Parameter Harmonic Flux Estimator (MPHFE). The latter is formulated such that the inductance, resistance, and stator current and its derivative are not necessary for the estimation of the harmonic eflux. This was achieved by forcing the harmonic current induced by the harmonic flux component to zero through the combined action of a Field-Oriented Controller (FOC) and a feed-forward controller. Subsequently, the harmonic flux can be obtained directly from the estimated harmonic back-EMF without the involvement of other motor parameters. Finally, the estimated flux is used in conjunction with a comprehensive analysis of the motor harmonic torque to determine the stator current compensation to eliminate the torque harmonic. A systematic approach to assign the parameter of the AFC controller were developed in this dissertation. Furthermore, multiple experiments were conducted to demonstrate the efficacy of the proposed control schemes harmonics.

Energy methods are widely used and well understood for determining the torque or force in machines which do not contain permanent magnets. Energy methods are employed to calculate torques or forces of magnetic origin after determination of the energy stored in the electromechanical coupling field. In this thesis, the energy stored in a permanent magnet system is defined, and the energy-coenergy relationship is determined. It is shown how residual magnetism can be incorporated into classical electromechanical coupling theory. It is therefore shown how equations for torques or forces can be derived for permanent magnet systems using energy methods. An analytical method of calculating permanent magnet reluctance torque is developed. The method uses an elementary expression for the magnetic field to obtain the stored energy. This enables an analytical expression for the reluctance torque waveform to be obtained. The method is demonstrated to provide a powerful and fast design tool. The method can be generally applied to reluctance torque problems where the airgap is reasonably smooth. The single phase synchronous permanent magnet motor is used in domestic appliances. It is a motor of very simple construction and high reliability, which is directly connected to an AC mains supply, and runs at synchronous speed. It is becoming increasingly used in preference to the shaded pole induction motor. However, its application is limited by the following characteristics. There is no control over the final direction of rotation, unless a mechanical blocking device is used. There are rotor positions at which only a very small starting torque is available. The characteristic twice electrical frequency torque pulsation yields a speed modulation of the same frequency, which can cause acoustic noise problems. A method of improving torque quality by improving the motor design is proposed to alleviate these limiting characteristics. This is achieved by designing a permanent magnet reluctance torque which cancels out the effect of the backward rotating component of the stator field. In this novel design, the permanent magnet reluctance torque effectively acts as a second balancing phase. An unconventional technique for starting a single phase synchronous permanent magnet motor is demonstrated. This technique uses an inductive reluctance torque, provided by placing a suitably shaped iron lamination on the rotor, to rotate the rotor to a position from which starting can occur.

La demanda d’aplicacions industrials avançades, fa que el control de màquines elèctriques de corrent altern (AC) sigui una disciplina contínuament creixent per satisfer l’alt nivell d’exigència. Tradicionalment, la màquina d’inducció (IM) ha estat la més utilitzada en aplicacions industrials de velocitat variable, incloent-ne bombes i ventiladors, màquines tèxtils i de paper, vehicles elèctrics, generació eòlica, etc. A més dels requeriments funcionals, l’estalvi energètic és, actualment, un aspecte a tenir en compte en aplicacions de velocitat variable. Una alternativa molt atractiva a la IM és la màquina síncrona d’imants permanents (PMSM). Entre d’altres avantatges, aquest tipus de màquines ofereixen una eficiència més elevada, alta densitat de potència i una resposta dinàmica molt ràpida. La demanda industrial de PMSM es situa en el rang de petita potència, encara que el interès en aquest tipus de màquines està creixent, en particular fins al rang dels 100 kW. Històricament, les màquines utilitzades en aplicacions de velocitat variable han estat alimentades per inversors de potència. En els últims anys, el convertidor matricial ha esdevingut un clar competidor del inversor convencional. Un convertidor matricial és un circuit de topologia avançada capaç de convertir directament AC en AC generant una tensió de càrrega amb amplitud i freqüència variable, amb flux de potència bidireccional, formes d’ona sinusoïdal tant a l’entrada com a la sortida i operant amb factor de potència unitari a l’entrada. A més, degut a que requereix no elements inductius ni capacitius per emmagatzemar energia, el disseny del convertidor matricial és molt compacte. Existeixen molts tipus de control per màquines de AC, essent els basats en control vectorial els més adequats per aplicacions de d’alt rendiment. Entre d’altres, el control de camp orientat i el control directe de parell son els més utilitzats. Tot i essent una de les tècniques emergents en aplicacions industrials, el control directe de parell té implícites una sèrie de limitacions que, encara avui, s’estan investigant. El treball presentat en aquesta tesi, s’endinsa en la investigació del control directe de parell per PMSM alimentats amb convertidors matricials. Aquest, treball considera el reemplaçament del inversor convencional per un convertidor matricial, explotant les característiques d’aquest per tal de reduir el arrissat del parell i del flux en la PMSM, inherent al control directe de parell. Durant el transcurs d’aquest treball s’ha desenvolupat un nou control directe de parell utilitzant vectors curts i llargs del convertidor matricial. Els efectes indesitjats de la tensió en mode comú, relacionada amb la utilització de convertidors de potència, és altre dels aspectes que s’aborden en aquest treball. Un algoritme molt simple que redueix la tensió en mode comú ocasionat pel control directe de parell amb convertidors matricials ha estat desenvolupat i investigat en aquesta tesi. La principal limitació de les tècniques “sensorless” basades en models o observadors és que fallen a baixes velocitats. La necessitat d’operar a baixa velocitat o velocitat zero, ha desencadenat la investigació d’altres tècniques on s’exploren les asimetries de la màquina a partir de la injecció d’un senyal d’alta freqüència per obtenir-ne la posició del rotor. Durant aquesta tesi s’ha desenvolupat un nou algoritme de injecció d’un vector rotatori en el pla  quan s’utilitza el control directe de parell.
The control of AC machine drives is a continuously advancing subject satisfying increasing high performance applications demands. Induction Motor (IM) drives with cage-type machines has been the workhorses of industrial variable speed drives applications, including pumps and fans, paper and textile mills, electric vehicles, locomotive propulsion, wind generation systems, etc. In addition to performance requirements, energy saving aspects of variable speed drives is gaining attention nowadays. Permanent Magnet Synchronous Machines (PMSM) are becoming a very attractive alternative to IM. Among other advantages, these type of machines offer higher efficiency, high power density and very fast dynamic performance. PMSM, in particular in the low power range, are already widely used in industry and recently, the interest in their application is growing, particularly up to 100 kW. Variable speed drives fed by voltage source inverters has been traditionally employed in industrial applications. In the past few years, matrix converters have emerged to become a close competitor to the conventional inverter. A matrix converter is an advanced circuit topology capable of converting AC-AC, providing generation of load voltage with arbitrary amplitude and frequency, bi-directional power flow, sinusoidal input/output waveforms, and operation under unity input power factor. Furthermore, since no inductive or capacitive elements are required, MC allows a very compact design. There are several methods to control AC machines, vector control methods being the most suitable for high performance demands. Among others, field oriented control and direct torque control are the most widely used. Although being one of the emerging control techniques for industrial applications, the direct torque control has some inherent drawbacks that are still being investigated by researchers. The work reported in this thesis is devoted to the investigation of direct torque control of PMSM drives fed by matrix converters. This work considers the replacement of the conventional voltage source inverter by a matrix converter. The features of matrix converters are exploited to reduce the inherent electromagnetic torque and stator flux ripples arising from the direct torque control driving a PMSM. A new direct torque control using small and large voltage vectors of matrix converters has been developed during the course of this work. The undesirable effects of the common mode voltage related with the utilization of the conventional voltage source inverter, like electromagnetic interferences and the machine early failures, are other issues with which this work is also concerned. A very simple algorithm to reduce the common mode voltage in direct torque control drives using matrix converters is developed and investigated in this work. The main limitation of all sensorless vector control schemes, based on the conventional fundamental frequency models or observers, is that they fail at very low speeds. The desirability to operate continuously at low or zero speed has led to another sensorless approaches where the saliency of the machine is tracked through some form of signal injection to obtain flux or position information. A new algorithm to inject a rotating vector in the a-b frame when employing a direct torque control has been developed in this thesis.

Electrical machines may exhibit various types of imbalances and undesirable harmonic distortions. These may increase the torque and flux ripples, acoustic noise, unbalanced three-phase currents, while also reducing efficiency. These types of imbalances and undesirable harmonic distortions cannot be controlled by using the conventional indirect torque control (ITC) and direct torque control (DTC) strategies. For some high-performance motion control, such as precision machine tools, robotics, and servo drives, low torque ripples are, however, obligatory. Nowadays, more studies have been conducted on the ITC strategy to control undesired current harmonics, such as double synchronic reference frames (DSRF), resonant controller, second order generalized integration, and reference current generation. Such strategies, however, can rarely be applied to DTC strategy. In this research, the influence of asymmetric winding impedances, unbalanced back-EMF, and inverter nonlinearity in three-phase surface-mounted PMSMs has been systematically investigated by employing space vector modulations (SVM) based ITC and DTC strategies. This thesis firstly presents a modified ITC strategy by extracting the positive and negative sequence components in the stationary abc frame, and then a coordination transformation is used to control the machine in DSRF. This strategy provides faster dynamic response when compared with the conventional DSRF strategy, since the filters and the decoupling network are not required. Due to the lack of research regarding the DTC strategy under unbalanced conditions, this research investigates and proposes modified cascaded and parallel DTC-SVM strategies. The conventional cascaded DTC strategy is investigated under balanced and unbalanced conditions. Then, a modified control strategy is introduced by adding two compensators (the conventional PI-controller with a resonant controller, and the use of the negative- and positive-sequence voltage vectors) to suppress the 2nd harmonic components in the torque and stator flux linkage. Furthermore, for parallel DTC-SVM, the compensation of the 2nd and 6th harmonic components is investigated by means of either a resonant controller or an adaptive filter. In addition to the simplicity of the proposed strategies, these may also be able to significantly reduce the torque and flux ripples, while maintaining the merit of the fast dynamic response of the conventional DTC strategy even under variable fundamental frequency. Moreover, it has been proven that the compensation from using a resonant controller or an adaptive filter is parameter independent. Thus, regardless of unbalanced conditions, an effective torque ripple minimisation can still be achieved by properly selecting the dominant harmonic compensation.

A number of important developments have led to an increasing attractiveness for very high speed electrical machines (either motors or generators). Specifically the increasing switching speed of power electronics, high energy magnets, high strength retaining materials, better high speed bearings and improvements in design analysis are the primary drivers in a move to higher speed. The design challenges come in the mechanical design in both terms of strength and resonant modes and in the electromagnetic design particularly in respect of iron losses and ac losses in the various conducting parts including the rotor.

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.

This doctoral study mainly considers the Wind Energy resource and focuses on the electromagnetic aspects of generators for direct drive solutions in this field. Despite the strong employing by many constructor of geared technology in Wind Turbines Generators, a transmission/gear box reduces both, eciency and reliability: the losses due to the transmission potentially compromise the sustainability of the electromechanical system. A better solution is the multipolar low speed direct drive train. Permanent magnet machines offer compactness and the absence of brushes with respect to traditional machines. Material in the armature can be saved using fractional slot windings. This type of machine exhibits many advantages such as short end windings, high slot fill factor, high efficiency and power density together with electrical redundancy, which allows the modularization of the active part and fault-tolerance capabilities. However, space harmonics of the magneto-motive force (MMF) in fractional slot windings lead to considerable rotor losses. The computation of these losses according to standard procedures (e.g. Steinmetz equation or models for massive body within homogeneous field) is not satisfactory. The MMF harmonics move asynchronously with respect to the rotor, inducing currents in any conductive rotor parts, e.g. the metallic iron yoke which supports the magnetic poles and the rare earth permanent magnets (PMs), acting on their working temperature which is strictly related to the performance of PMs. The reduction of the residual ux density causes a decrease both in the back electromotive force (EMF) and in the electromagnetic torque. The reduction of the magnetic eld increases the risk of an irreversible demagnetization of the PMs. The MMF space harmonic amplitude and frequency depend on the particular combination of number of slots and poles. The amount of such losses increases dramatically with the size of the machine becoming a crucial aspect in the design of a large diameter (v 2 - 3m) multipolar direct drive generators with PMs. A proper selection of the winding of the machine,fixing the number of slot and poles represents an improvement in the sustainability of the electromechanical conversion process: losses are limited and a higher eciency is achieved. If efficiency is better even less active material is wasted. This part of the doctoral study has been accomplished at the Electric Drives Laboratory at the Department of Industrial Engineering of the University of Padova during a partnership with Leitwind A.G.(in Sterzing, Italy), which operates in the Wind Energy Market. The aim is to design a large diameter generator (v 4m), which will be employed in the prototype of a 3 MW wind turbine. The will of Leitwind to implement a method to predict rotor losses in large machines with permanent magnet and fractional slot windings is the key basic point to be solved. The existing LW15C generator for LTW77 (1.5 MW rated power) wind turbine is analyzed by means of analytical relations and finite elements: it represents the starting point of this study. A method to calculate rotor losses due to the high harmonic contents of the fractional slot winding is applied. Such estimated losses are then compared with the results of experimental test benches with "full-scale" prototypes. The same study is then repeated on SFA motor (500 kW rated), employed in ropeways transport in Leitner A.G. plants. Both Leitner and Leitwind belong to the Leitner Technologies Group. Test bench results are finally compared with the values from the analysis. Starting from both the experience on LW15C generator and SFA motor the design of LW30A prototype generator for Leitwind 3MW wind turbine is chosen. Dierent topologies of PM machines with fractional slot winding are then investigated and compared with the switching ux configuration (SFPM), both with rare earths and ferrite PMs. The possibility to integrate a huge magnet quantity in the armature of the SFPM machine and the ux concentration principle can lead to a cost eective solution which must be carefully evaluated without considering the performance of the machine only. The structure of the rotor is robust and simple, like in classical reluctance machines. The robustness against PMs demagnetization is a crucial point to investigate. To extend the scenario of renewable energy, the wave energy resource is brie y overviewed and some topologies for linear direct drive generator in this field are investigated. In order to increase the thrust density the possibility of employing a double-sided structure is analyzed. The employing of ferrite PMs is also considered: despite their low energy with respect to rare earth magnets they have a lower impact on environment and human health. The extraction process of ferrite is similar to the iron one, while rare earths must be separated from radio elements. Main contributions of the thesis To the knowledge of the author, the contributions of this thesis for the upcoming researchers in electrical machines for renewable energy eld are: • The application of straight lined model and of the current sheet method to calculate rotor losses in large direct drive permanent magnet machines. The results of the test bench activity on real machines are then described and compared with the prediction. • Selection of number of slots and poles for fractional winding direct drive large generators. • Comparison of the switching ux machine with other well known machine topologies, including demagnetization behavior and ferrite PMs, more sustainable than rare earth ones. • Investigation on dierent linear modules topologies for wave energy, including double side switching ux topology. Outline of the thesis Chapter 1 provides an overview on renewable energy conversion field and presents the company Leitwind A.G. Chapter 2 describes the analysis and modeling of the LW15C generator for 1.5 MW wind turbine. Then a similar study has been performed for the SFA motor for ropeways applications. Both analytical and finite elements model have been developed/implemented and are compared to the results of experimental test bench activities. The same models are applied to the analysis of the new LW30A generator. Chapter 3 faces the topic of rotor losses in order to model them with the straight lined model and the current sheet method. The rotor losses computation is considered and described. Predicted values are compared with the test bench ones. Chapter 4 establishes a scaling law for rotor losses in fractional slot PM machines. Chapter 5 provides the selection of the number of slots and poles to design the new LW30A generator for 3.0 MW wind turbine. The validity of the Index of Rotor Losses obtained from the straight lined model is investigated and applied. Chapter 6 describes the comparison of fractional winding machine with a small switching ux permanent magnet machine, both with rare earth and ferrite PMs. The demagnetization behavior of the different machine topologies is analyzed. Chapter 7 considers linear drives for Wave energy conversion with different topologies, including the double side switching flux machine
Questo lavoro di dottorato considera principalmente la Risorsa Eolica e si focalizza sulle caratteristiche elettromagnetiche dei generatori a presa diretta per questa applicazione. Malgrado molti Costruttori di turbine eoliche usino congurazioni comprendenti il moltiplicatore di giri, la presenza di quest'organo di trasmissione causa una perdita di ecienza del sistema elettromeccanico che va a comprometterne la sostenibilità. Una soluzione multipolare a bassa velocita di rotazione e presa diretta tra generatore e pale della turbina e quindi adottata. Si sceglie l'utilizzo del magnete permanente grazie alla sua compattezza e all'assenza di spazzole in paragone alle soluzioni di macchina sincrona tradizionale. L'avvolgimento frazionario e adottato per risparmiare materiale nell'avvolgimento di armatura della macchina. Questo tipo di congurazione presenta evidenti vantaggi come la lunghezza ridotta delle testate, il buon fattore di riempimento delle cave, elevati rendimento e fattore di potenza. Essa si presta inoltre a soluzioni circuitalmente ridondanti che consentono una struttura modulare della parte attiva, con la capacita di tollerare i guasti. D'altro canto, le armoniche spaziali della forza magneto motrice (MMF) dovuta all'avvolgimento frazionario causano perdite nel rotore di entita notevole. I metodi tradizionali di calcolo delle perdite (formula di Steinmetz o modelli di corpi solidi in campo magnetico uniforme) non forniscono risultati soddisfacenti per queste perdite. La forza magneto motrice risulta non sincrona con il rotore della macchina, con conseguente indursi di correnti parassite in ogni parte conduttrice del rotore, come nel giogo metallico che sorregge i poli magnetici e nei magneti stessi (terre rare). Le perdite nei magneti ne causano il riscaldamento, con conseguente calo delle prestazioni della macchina. La riduzione del campo dei magneti dovuta all'aumento di temperatura aumenta il rischio di smagnetizzazione irreversibile. L'ampiezza delle armoniche spaziali di forza magneto motrice e la loro frequenza vista dal rotore dipendono dalla particolare combinazione cave{poli dell'avvolgimento scelto. L'entita di queste perdite cresce notevolmente con l'aumentare delle dimensioni della macchina, divenendo un aspetto cruciale nella progettazione di macchine multipolari a presa diretta di grande diametro (. 2m) con magnete permanente. Una scelta adeguata del rapporto cave{poli dell'avvolgimento, signica un notevole miglioramento della sostenibilita del processo di conversione elettromeccanica: le perdite vengono ridotte e il rendimento migliora. Se il rendimento migliora, signica che meno materiale e stato sprecato. Questa parte del lavoro di tesi si e svolta presso il Laboratorio di Azionamenti Elettrici nel Dipartimento di Ingegneria Industriale dell'Universita di Padova nell'ambito di un contratto di ricerca voluto da Leitwind SpA (VIpiteno, Italia). Leitwind e un costruttore di turbine eoliche. Lo scopo e progettare un generatore di grande diametro (v 4m) per il prototipo di turbina eolica da 3 MW. Compresa l'importanza del fenomeno delle perdite rotoriche, la volonta di Leitwind e svilupparne calcolo per scegliere l'avvolgimento della nuova macchina. Il generatore Leitwind esitente, denominato LW15C, per la turbina LTW77 (potenza nominale 1.5 MW) e analizzato sia con modelli analitici che con gli elementi niti. Questo generatore e la base di partenza di questo studio. Viene applicato un metodo per il calcolo delle perdite rotoriche indotte dall'elevato contenuto armonico dell'avvolgimento frazionario. Le perdite cos ottenute sono confrontate con i risultati dell'attivita del banco prova su macchine reali. Con lo stesso approccio si studia e si modella il motore diretto per trazione funiviaria SFA (500 kW di potenza nominale) negli impianti Leitner. Leitner e Leitwind appartengono al Gruppo Leitner Technologies. I risultati del banco prova sono confrontati con i valori calcolati. La progettazione del nuovo generatore LW30A e sviluppata a partire dai modelli creati per il generatore LW15C e il motore diretto SFA. Vengono poi studiate dierenti topologie di macchina a magnete permanente con avvolgimento frazionario per confrontarle con la congurazione switching ux (SFPM). Lo studio prende in considerazione sia magneti di terre rare, che di ferrite. La possibilità di integrare una notevole quantita di magnete nella parte di armatura della macchina SFPM e il principio di concentrazione di usso portano ad una soluzione con un buon rapporto costi prestazioni, che pero deve essere valutata non solo da un punto di vista di prestazioni. La struttura del rotore di questa macchina e semplice e robusta, come per le macchine a riluttanza. Il comportamento della topologia SFPM a smagnetizzazione dei magneti permanenti risulta un punto cruciale da indagare. Per allargare lo studio ad un'altra Fonte Rinnovabile, l'energia da moto ondoso e brevemente descritta e vengono confrontate alcune topologie di generatori lineari per questa applicazione. Uno struttura a doppio statore viene studiata con l'intento di massimizzare la spinta sulla parte mobile. Si considera inoltre l'utilizzo dei magneti in ferrite: malgrado il loro basso prodotto di energia rispetto ai magneti in terre rare, essi risultano meni nocivi per l'ambiente e la salute dell'uomo: il processo di estrazione delle terre rare coinvolge infatti elementi radioattivi, mentre l'estrazione della ferrite e in tutto simile a quella del ferro. Contributi principali della tesi I principali contributi di questo lavoro di tesi alla ricerca futura nell'ambito delle energie rinnovabili si possono cos sintetizzare: • L'applicazione del modello a strati e del metodo dei punti corrente nel calcolo delle perdite rotoriche di macchine elettriche a presa diretta di grande diametro, con magneti permanenti. I risultati dell'attivita sperimentale su banco prova di grosse macchine reali sono confrontati con i valori calcolati. • La scelta del numero di poli e di cave nella progettazione di macchine a presa diretta di grande diametro, con avvolgimento frazionario. • Confronto della macchina switching ux con topologie di macchina note, comprendendo la smagnetizzazione del magnete e l'utilizzo della ferrite, materiale più sostenibile delle terre rare. • Studio di diverse topologie di generatore lineare per generazione da moto ondoso, includendo la topologia switching ux a doppio statore. Struttura della tesi Capitolo 1 : presenta una breve panoramica sull'energia rinnovabile eolica e da moto ondoso e descrive l'azienda Leitwind SpA. Capitolo 2 : descrive la modellazione e l'analisi delle macchine studiate, sia con metodi analitici che con gli elementi niti: sono inclusi i risultati dell'attivita sul banco prova. I modelli, sviluppati sul generatore LW15 e sul motore SFA sono poi applicati al nuovo generatore LW30A. Capitolo 3 : aronta la tematica del calcolo delle perdite rotoriche, sviluppando il modello a strati e il metodo dei punti corrente. Viene descritto il calcolo delle perdite rotoriche. Si aronta la validazione dei metodi di calcolo al banco prova. Capitolo 4 : ricava una legge di scala per le perdite rotoriche per macchine a magnete permanente ad avvolgimento frazionario. Capitolo 5 : presenta la scelta del rapporto cave{poli nel progetto del nuovo generatore LW30A per la turbina da 3.0 MW LTW 101. Viene investigata la possibilità di applicare l'Indice delle Perdite Rotoriche, ricavato dal modello a strati. Capitolo 6 : confronta diverse topologie di macchine ad avvolgimento frazionario con la congurazione switching ux, sia con terre rare che con ferrite. Si aronta il fenomeno della smagnetizzazione sulle diverse topologie di macchina. Capitolo 7 : prende in considerazione topologie di macchina lineare per conversione da moto ondoso. Include la congurazione switchng ux a doppio statore

This thesis investigates the application of the synthetic loading technique for efficiency evaluation, of permanent magnet (PM) synchronous machines. The standard tests require specialist test facilities, additional machines, and for large machines, linear machines, or vertical mounted machine and floor space. Therefore, an efficiency test method that avoids the need for an external mechanical load is desirable. Synthetic loading can determine machine losses and eliminates the need for a mechanical load connected to the test machine. The synthetic loading technique forces the machine under test to accelerate and decelerate thereby alternating between motor-generator action. If configured correctly the machine, on average over each synthetic loading cycle, operates at rated rms current, rated rms voltage and rated speed, thus producing rated copper loss, iron loss and friction and windage loss. The thesis considers how to properly configure synthetic loading for PM synchronous machines. A derivation of the mathematical models of the synthetic loading technique applied to the permanent magnet synchronous machines is provided in the thesis. The model is based on the direct and quadrature axis equivalent circuits. From the mathematical model, a quadrature axis current algorithm is proposed which is used to develop the speed equation and the stator direct and quadrature axis voltage and current equations. The thesis also establishes a generalised mathematical model of the synthetic loading technique for permanent magnet synchronous machines. Using the derived equations, the effects of synthetic loading frequency on the dc link voltage and the inverter phase-leg volt-ampere rating are analysed. This shows that the synthetic loading technique requires an increased dc link voltage and inverter volt-ampere rating compared to the standard efficiency test technique. A test rig is constructed and used to assess synthetic loading for fractional hp machines. The research verifies the synthetic loading technique experimentally for three permanent magnet synchronous machine types: the surface-mount PM synchronous machine, the interior PM synchronous machine and the linear PM synchronous machine. Simulation and experimental results from synthetic loading are compared with the standard efficiency test. The simulation and the experimental results show that the synthetic loading technique is capable of evaluating the efficiency of the permanent magnet synchronous machines. The key contributions of this work concerns the mathematical model of PM synchronous machines under synthetic loading, the hardware and software implementation and validation of synthetic loading as a technique for efficiency evaluation of PM synchronous machines.

Permanent Magnet machines have been increasingly used in high-speed applications due to the advantages they offer such as higher efficiency, output torque and, output power. This dissertation discusses the electrical and magnetic design of permanent magnet machines and the design and analysis of two 10 kW, 30000 rpm Interior Permanent Magnet (IPM) machines. This dissertation consists of two parts: the first part discusses high-speed machine topologies, and in particular the permanent magnet machine. Trends, advantages, disadvantages, recent developments, etc. are discussed and conclusions are made. The second part presents the design, analysis and testing of interior permanent magnet machines for a high-speed application. The machines are designed from first principles and are simulated using Ansys Maxwell software to understand the finite element analysis. In order to obtain a fair comparison between the machines, the required output criteria was used as the judging criteria (10kW, 30000 rpm). As a result, the rotor diameter, stator diameter, airgap length, and stack length were kept the same for both machines. The winding configuration was set as distributed windings, however the number of turns and other details were kept flexible in order to be able to obtain the best design for each machine. Similarly, the magnet volume was kept flexible as this could be used as a comparison criteria relating to the cost of the machines. The two IPM topologies are compared with respect to their torque, magnetic field, airgap flux, core loss, efficiency, and cost. The radial IPM produces a smoother torque output, with lower torque ripple, and has lower losses compared to the circumferential IPM which produces a higher torque and power output. Furthermore, the circumferential IPM also experiences much higher torque ripple and core losses, both of which are highly undesirable characteristics for high-speed machines. In addition, the circumferential IPM has a much more complex manufacturing process compared to the radial IPM which would significantly increase the cost of prototyping the machine, thus the radial IPM was selected for prototyping and brief experimental analysis. The radial IPM has been experimentally tested under no-load conditions. These results were successfully compared to the simulated and analytical results to show correlation between the design and experimental process. Potential areas of further work may include conducting detailed loss analysis to understand the effects that changing various design parameters has on the core loss and overall performance. Detailed thermal and mechanical analysis of the machines may also result in interesting conclusions that would alter the design of the machine to make it more efficient.

The adoption of permanent magnet (PM) on rotating electrical machines represents now a fashionable design option in all elds as transportation, industrial processing, power plants, domestic appliances, actuators and so on. The corresponding power ratings of such machines ranges now from fractions of Watts to some million of Watts, as in a wind generator. Actually, among the electrical machines, the PM synchronous machine is the more deeply studied from academia and industry. In particular, the PM synchronous machine combines several advantages as high effciency, high power factor, high torque density, high overload capability, robustness, reduced maintenance, compactness and low weight. These advantages are becoming crucial for those non-industrial application, as the electric vehicles. High performance and compactness are often the winning characteristics of such machines as respect to the induction machines. Referring to the automotive eld, variable speed drives as PM synchronous machine are adopted to improve the overall performance of the vehicles. The design exibility due to the absence of rotor winding excitation and the variety of PM sizes and characteristics allow to achieve several features, e.g. fault-tolerance and fux-weakening capability. Thanks to these features the PM machine is a suitable candidate for traction requirements. However the recent trend is to select those congurations that allow to minimize the PM utilization. It is also due to the issues related to PM temperature derating, mechanical stress, and PM reliability. The PM synchronous reluctance machine or interior PM machine is, among the others, a promising candidate to satisfy the traction requirements. Thanks to its anisotropy rotor structure is able to provide torque not only due to the PM ux. In addition the adoption of fractional-slot winding, as respect to the standard integral-slot winding, is imperative to achieve some of the appealing features. In this field, several topics are under study by the international community of researchers. However, the aim of the doctoral work is to deepen some aspects concerning the design of these machines. It is worth noticing that the complexity of the rotor structure of these machine involves several drawbacks, such as torque oscillations, additional iron losses, vibrations, and so on. Therefore, some aspects have been analyzed by means of analytical procedures, nite element simulations and experiential measurements on prototypes. The variety of topic treated is directly due to the complexity of the design: a tradeo between advantages and drawbacks is usually necessary rather than a perfect minimization of a single aspect. Therefore, an overview of the design options is required in order to design a suitable machine. In the contest of the analysis of the interior permanent magnet machines, the objectives can be summarized as: 1) To evaluate how the rotor geometry aects the torque ripple, and thus the solutions allowing to minimize it. 2) To evaluate how the rotor geometry aects the eddy current iron losses in the stator teeth, and thus the solutions allowing to minimize it (in particular referring to the fux-weakening operating conditions). 3) To deeply investigate the torque mechanism and complex magnetic phenomena, in particular adopting fractional-slot winding. 4) To investigate a particular conguration of fault-tolerant machine, the dual three-phase machine provided of a suitable anisotropic rotor. To the knowledge of the author, the remarkable contribution of this thesis for future researchers in this eld are: 1) An analytical model of the anisotropic synchronous machine that can be simply adopted to evaluate optimal solutions allowing to satisfy selected objectives. It has been applied to the issues of torque ripple minimization and stator tooth eddy current minimization. The model has been veried experimentally comparing the measured and predicted stator tooth flux density. 2) An extended analysis of the dual three-phase machine provided of an interior permanent magnet rotor, supported by experimental verication. A simple design rule to select the appropriate number of slots and poles in order to achieve a six- phase machine is proposed.
L'utilizzo dei magneti permanenti nel campo delle macchine elettriche rotanti attualmente rappresenta una scelta comune e vantaggiosa nella quasi totalità delle applicazioni: ad esempio il trasporto, i processi industriali, gli impianti di generazione, gli attuatori, gli elettrodomestici. Le potenze di queste macchine elettriche spaziano dalle frazioni di Watt ai milioni di Watt. Tra le varie tipologie di macchine elettriche provviste di eccitazione mediante magnete permanente, le macchine sincrone a magnete permanente occupano un posto di rilievo nella ricerca, sia in ambito accademico che industriale. In particolare queste macchine sincrone permettono di combinare più vantaggi, come alto rendimento, elevato fattore di potenza, alta densità di coppia, notevole capacità di sovraccarico, robusta costruzione, limitata manutenzione, volumi compatti e quindi peso ridotto. Negli ultimi anni questi vantaggi stanno diventando delle caratteristiche cruciali e preferibili, in particolare per le applicazioni non prettamente industriali come la trazione elettrica dei veicoli. Infatti, per queste nuove applicazioni, la compattezza dei volumi e le alte prestazioni in termini di coppia e rendimento sono le caratteristiche vincenti che li fanno preferire ai motori asincroni. Nell'ambito automobilistico le macchine elettriche a velocità variabile, come i motori sincroni a magnete permanente, sono attualmente sempre più utilizzati per migliorare le prestazioni complessive dei veicoli. In aggiunta ai vantaggi già indicati, i motori a magnete permanente permettono una notevole fessibilità di progettazione. L'assenza di avvolgimento di eccitazione rotorico ha permesso di studiare varie di strutture. Conseguentemente, grazie a progettazioni dedicate, è possibile ottenere macchine che esibiscono una capacità di tollerare alcuni guasti o macchine in grado di operare lungo un campo di velocità estremamente esteso. Queste peculiarità sono spesso richieste dalle applicazioni di mobilità, come il trasporto, che richiedono inoltre un alto livello di affdabilità. Nonostante questi indubbi vantaggi sussistono delle problematiche legate all'utilizzo dei magneti permanenti. La tendenza odierna è, quindi, quella di studiare le congurazioni che permettono di limitare o minimizzare la quantità di magnete permanente, pur soddisfando le richieste di progetto. Tra le soluzioni proposte, i motori sincroni a riluttanza assistita dai magneti permanenti o più semplicemente i motori a magnete interno rappresentano una valida scelta adatta alle richieste nel campo del trasporto. Grazie ad una struttura rotorica anisotropa, questi motori sono in grado di produrre coppia utile anche in assenza di magnete permanente. L'utilizzo dei magneti permanenti permette di migliorarne le prestazioni eliminando alcuni svantaggi. Questi motori sono oggetto di studio di un gran numero di gruppi universitari di ricerca. Lo scopo di questa tesi di dottorato è analizzare in dettaglio alcuni aspetti di progettazione elettromeccanica delle macchine sincrone a magneti permanenti interni. Infatti la complessa struttura geometrica rotorica, che permette di ottenere i noti vantaggi, determina anche una serie di problematiche. In generale, queste macchine elettriche sono caratterizzate da elevate oscillazioni di coppia, distorsioni dei fussi magnetici e conseguenti perdite nel ferro, vibrazioni, ed altri eetti parassiti. Quindi, l'obiettivo della tesi è analizzare alcuni di questi aspetti mediante procedure analitiche, simulazioni agli elementi niti e prove sperimentali al ne di valutare regole di progettazione che permettano di minimizzare gli svantaggi dei questa congurazione. Nel ambito dell'analisi delle metodologie di progettazione del motore a magneti permanenti interni sono state arontate le seguenti tematiche di studio: 1) Investigare gli eetti della geometria rotorica sull'oscillazione di coppia ed individuare le soluzioni che permettono di minimizzare questo fenomeno. 2) Investigare gli eetti della geometria rotorica sulle uttuazioni dell'induzione nei denti statorici, e le conseguenti perdite nel ferro per eetto delle correnti parassite. In questo contesto, individuare le soluzioni che permettono di limitare le perdite alle alte velocità in condizioni di defussaggio. 3) Investigare il principio di produzione della coppia elettromagnetica, in particolare della componente non legata ai magneti permanenti, ed analizzare alcuni eletti parassiti legati all'utilizzo di avvolgimenti a passo frazionario. 4) Investigare una particolare macchina, il motore a doppio avvolgimento trifase, che permette di ottenere un aumento della tolleranza ai guasti pur richiedendo componentistica standard.