Dissertations / Theses on the topic 'Magnet losse'

A closed-loop computer-controlled single-sheet test system has been developed to characterise lamination materials and to measure, the iron loss density under any specified flux density waveform. The system has been 'used to validate predictions from a recently developed theoretical model, for the calculation of the excess loss component associated with domaiQ wall movement, under flux density waveforms typical of those encountered in the stator core of brushless permanent magnet dc motors. In addition, an improved expression for the calculation of the iron loss density component, from measured 71 and 7!vectors, due to rotatio~ in non-purely rotating flux conditions, has been derived. A simple analytical model from which the airgap flux density and spread of magnet working points can be determined and which accounts for the effects of curvature for radial-field permanent magnet machines has been developed and validated. The model has been coupled to an analytical technique for the prediction of the open-circuit flux density waveforms in different regions of the stator core, and has subsequently been employed for the prediction of the open-circuit iron loss. In order to predict the iron loss under any specified load condition, a technique which couples a brushless dc drive system simulation to a series of magnetostatic finite element analyses corresponding to discrete instants in a commutation cycle has been developed. It enables the prediction of the local flux density waveforms throughout the stator core under any operating condition, and has been employed to predict the local iron loss density distribution 'and the total iron loss and their variation with both the load and the commutation strategy, Finally, the theoretical findings have been validated against measurements on a representative low power brushless drive system.

This thesis presents a study on core loss calculations in rotating electrical machines. The basic concepts concerning magnetic moments, ferromagnetism, magnetic domains and magnetic hysteresis are introduced. The three-term models for alternating and rotational core losses in electrical steel sheets are presented. Several core loss measurement techniques are reviewed and an experiment is carried out to measure the total core losses in an electrical sheet steel sample under alternating and rotational magnetic fields of various frequencies and amplitudes. The coefficients in the loss models for alternating and rotational core losses are obtained through curve fitting process. The theory of electromagnetic fields is presented through the Maxwell equations and field scalar equations. A detailed review on core loss models for rotating electrical machines is presented. A rotational core loss model is adopted to calculate the core losses in a PM motor. The total core loss in the PM motor is obtained by summing the element losses using a MATLAB program. An experiment is conducted to measure the total core loss in the PM motor. The calculated total core loss in the PM motor is compared with the experimental results. The calculated total core losses are about 19% lower than the tested results. Various possible causes for this discrepancy are discussed
Master of Engineering (Hons)

This master thesis deals with the estimation of magnet losses in a Permanent Magnet(PM) motor inserted in a nut-runner. This type of machine has interesting featuressuch as being slot-less and running at a very high speed (30000 rpm). An extensiveliterature review was performed in order to investigate the state of the art in estimationof the losses in magnets of a PM machine. Analytical models to calculate the no-loadback-emf and the magnetic ux density in the air-gap due to the currents in the statorare presented rst. Furthermore, several of the analytical models for calculating lossesin magnets described in the literature were tested and adapted to the case of a slotlessmachine with a parallel-magnetized ring. Then, a numerical estimation of thelosses with nite element method (FEM) 2D was carried out. In addition, a detailedinvestigation of the eect of simulation settings (e.g., mesh size, time-step, remanentmagnetic ux density in the magnet, superposition of the losses, etc.) was performed.Finally, calculation of losses with 3D FEM are also included in order to compare thecalculated losses with both analytical and FEM 2D results. The estimation of thelosses includes the variation of these with frequency for a range of frequencies between10 and 100 kHz.
Detta examensarbete handlar om uppskattningen av magnetforluster i en permanentmagnetmotor (PM) inford i en mutterdragare. Denna typ av maskin har intressantafunktioner, som att den ar slot-less och att den kors i en hog hastighet (30000rpm). En omfattande litteraturstudie utfordes for att kunna uppskatta forluster imagneterna pa basta satt. Forst presenteras analytiska modeller for att berakna denelektromotoriska kraften (EMK) och den magnetiska odestatheten i luftgapet somuppkommer pa grund av strommarna i statorn. Dessutom har era av de analytiskamodellerna for berakning av forlusterna som beskrivits i litteraturen testats och anpassatstill en slot-less maskin med en parallelmagnetiserad ring. En numerisk uppskattningav forlusterna har sedan utforts med hjalp av nita elementmetoden (FEM) 2D.Dartill har en detaljerad undersokning genomforts hur olika parameterinstallningarpaverka utfallet. De FEM parametrar som har undersokts har bland annat bestattav berakningsnatets storlek, tidssteg, remanens odestatheten i magneten och om superpositionav forlusterna galler. Till sist har berakningar for forluster med 3D FEMutforts och jamforts med resultaten for bade de analytiska och FEM 2D resultaten.Uppskattning av forluster innefattar variationen av dessa med ett frekvensomrade mellan10 och 100 kHz.

This thesis presents a study on core loss calculations in rotating electrical machines. The basic concepts concerning magnetic moments, ferromagnetism, magnetic domains and magnetic hysteresis are introduced. The three-term models for alternating and rotational core losses in electrical steel sheets are presented. Several core loss measurement techniques are reviewed and an experiment is carried out to measure the total core losses in an electrical sheet steel sample under alternating and rotational magnetic fields of various frequencies and amplitudes. The coefficients in the loss models for alternating and rotational core losses are obtained through curve fitting process. The theory of electromagnetic fields is presented through the Maxwell equations and field scalar equations. A detailed review on core loss models for rotating electrical machines is presented. A rotational core loss model is adopted to calculate the core losses in a PM motor. The total core loss in the PM motor is obtained by summing the element losses using a MATLAB program. An experiment is conducted to measure the total core loss in the PM motor. The calculated total core loss in the PM motor is compared with the experimental results. The calculated total core losses are about 19% lower than the tested results. Various possible causes for this discrepancy are discussed

Thesis (M.Sc (Hons)) -- University of Western Sydney, Nepean, 2000.
"Submitted for the degree of Master of Engineering (Hons), School of Mechatronic, Computer & Electrical Engineering, University of Western Sydney, Nepean" Includes bibliographical references (leaves 107-114).

High-speed permanent magnet machines are currently being developed for a number of applications including gas-turbine generator sets and machine tools. Due to the high peripheral speed of the rotor and the relatively high conductivity of the magnets used, rotor eddy current loss can be substantial. Quite low levels of loss may present a serious problem if rotor cooling is poor. The accurate calculation of these losses, and appreciation of their dependence on machine parameters, are therefore of great importance for reasons of both efficiency and temperature rise. In this, thesis, a method has been developed to evaluate the asynchronously rotating harmonics with respect to the rotor and to calculate rotor power loss caused by these harmonics. The harmonics are determined by double Fourier analysis of the normal flux density data over the rotor surface. The data is obtained from finite element magnetostatic analysis of the machine at different rotor positions, with all possible harmonic sources present, except rotor induced eddy currents whose effect on harmonics was found to be negligible. Rotor power loss is calculated for each harmonic using a 2D rectilinear current sheet model of the machine. The magnitude of the current sheet, which is placed on the inner surface of a toothless stator, is adjusted to produce the same magnetostatic normal flux density over the rotor surface as that of the corresponding harmonic. The 2D current sheet model does not allow for 3D end effects and magnet segmentation. The accuracy of the analytical rectilinear current sheet model was verified by comparison with a cylindrical FE current sheet model, and by solving a benchmark eddy current problem that can be also solved using FE steady-state AC analysis. The current sheet model was used to calculate rotor loss in a number of generic machines, with two basic types of rotor construction: 1) non-salient rotor with arc shaped surface magnets and 2) salient rotor with chord shaped surface magnets. The results show that rotor loss depends strongly on the ratio of slot opening to slot pitch (s/X.) and on the ratio of total airgap to slot pitch (g/X). For the same fundamental airgap flux density, rotor loss reduces dramatically by increasing airgap length and reducing slot opening. Increasing the number of slots also reduces the loss. The results also show that rotor loss in a generator increases as the power factor moves from lagging to leading due to the armature reaction effect. Using a conducting sleeve, instead of a non-conducting one, with conductivity in the range of practical values, increases rotor losses dramatically. Reducing magnet conductivity reduces rotor loss. Rotor power loss in machines with non-conducting sleeve is concentrated on the surface of the magnet and a small part on the surface of the hub. In machines with chord shaped magnets, the power loss density can be very high in the parts of the steel hub near the intersection of two poles where local total airgap is small. The harmonics caused by inverter switching in a motor or rectifier switching in an alternator can cause a very significant increase in rotor loss, compared to a machine with a sinusoidal mmf. The results also show that the loss depends strongly on the switching strategy, e.g., switching harmonics in 6 step mmf waveform produce 3 times more loss than a 12 step mmf waveform. Although the developed method for calculation of rotor power loss does not take the effect of magnet peripheral discontinuity or segmentation into account, it is clear that segmentation reduces power loss by interrupting the eddy current return path, specially for harmonics with long wavelengths. The effect of segmentation requires further study.

Work had been established for traction machine design aspects in this research. The effect of multiphase design for Permanent Magnet (PM) machine was investigated. The electromagnetic characteristics of both 3-phase and 9-phase machine, along with different magnet designs, were simulated and analyzed by using the program developed during the process. The software used were FEMM and MATLAB. The iron loss for different designs was established, based on the analytical flux density obtained by 2-D stepping FEA method. The harmonic of flux waveform and rotating field were also considered for difference areas in the machine models. The prediction was compared with experimental data collected in open circuit. The simulation result shown that there was a minimum 4% torque gain and noticeable less torque ripples for 9-phase machine, comparing with 3-phase one, with the same excitation phase current. The embedded magnet rotor design was suggested to monitor the demagnetization of each magnet closely, since some area of the magnet could be demagnetized even when the working point of magnet was well distance away from the nonlinear region of its characteristic. There were about 6% less iron loss was produced in 9-phase model than 3-phase model. The implemented method for calculating iron loss was more accurate within 3500 rpm rotor speed comparing with other approaches.

Rotor electromagnetic losses can be problematic in high speed permanent magnet synchronous machines, especially when the speed or the electrical loading are high and the slotting and winding configuration results in high magnitude asynchronous harmonics. Accurate estimation of these travelling flux harmonics in the initial design stage is essential, as small errors can result in significant errors in the estimated rotor losses, which could lead to misinformed design decisions. This Thesis makes a number of contributions to the subject of rotor losses in PM machines. It firstly investigates the accuracy of the commonly used current sheet method for estimating losses for each harmonic. In this method, the losses are calculated using a multi-layer model of the machine in which each asynchronous harmonic in the rotor frame is represented by current sheet on the surface of the bore of a slotless stator. The harmonics are calculated using double Fourier transform of flux density data on the surface of the magnet obtained from a number of magnetostatic finite element (FE) solutions at different rotor position. The losses are also calculated using 2D transient FEA with rotor motion, with appropriate mesh refinement and time step determined based on a mesh and time step dependence study. The results show that the current sheet method accurately calculates the losses in ring magnets if the amplitudes of the harmonics are estimated accurately. Secondly, the Thesis extends 3 analytical methods that have been reported in the literature by Zhu and Howe (1993), Gieras (2004) and et al (2006) to estimate the amplitude of the no-load asynchronous travelling flux density harmonics, the magnet flux tooth ripple harmonics, in the rotor frame. The accuracy of these methods is evaluated by comparison to those calculated using non-linear finite element analysis for variants of a particular machine. The results show that ( et al, 2006) complex permeance method provides the closest estimate, when the level of saturation in the machine is negligible. However, if the saturation, of the tooth tip in particular is significant, then all methods underestimate the amplitudes of the harmonics. And accordingly, the estimated rotor losses are grossly underestimated by a factor of 1:3 in a machine with heavy tooth tip saturation. Thirdly, the Thesis tackles the problem of losses in a loaded generator with sinusoidal currents. It is shown that the total losses in the machine are dependent on the power factor and the phase angle between the emf and current. The total loss cannot be simply calculated by adding the no-load loss due to magnet flux tooth ripple harmonics and the loss due to stator mmf asynchronous harmonics. This is due to the interaction between the stator mmf harmonics and the magnet flux tooth ripple harmonics, which need to be added vectorially. This is verified by comparing the results calculated analytically (using the most accurate ’s meth d f calculating no-load harmonics), with those obtained from transient FEA in a machine with no significant saturation. Fourthly, the Thesis investigates rotor losses in a generator with two slots per pole per phase connected to an uncontrolled diode rectifier, considering the two cases of constant current and constant voltage dc link. Two winding and rectifier configurations are considered: a 3-phase winding with a 3-phase, 6 pulse bridge rectifier and a double 3-phase winding with a 3-phase rectifier each, connected in series i.e., a 12 pulse rectifier. Both magnet flux tooth ripple and armature reaction stator mmf harmonics are considered in the calculation of rotor loss; the harmonics were added vectorially. It is shown that the machine with double 3-phase windings and 12 pulse rectifier has considerably lower rotor losses that the machine with one single 3-phase winding due to cancellation of high order harmonics. Finally, limited studies are performed in the Thesis for the calculation of rotor losses in PMSGs with different slot opening, number of slots per pole and airgap (with magnet thickness adjusted to keep the airgap flux density and emf constant). It is shown that increasing the airgap and reducing slot opening reduced the losses The results plotted in a normalised form of loss per unit rotor surface area are versus the ratios of gap/slot pitch and slot opening divided by pole pitch. These curves are shown to give reasonable quick estimates of rotor losses in machines with different sizes. Also, rotor losses are calculated in three PMSGs with different numbers of slots per pole and winding / rectifier configurations. The results show that the popular 1.5 slots per pole concentrated winding configuration have considerably higher rotor losses due to the strong second harmonic than the other machines with lap windings. The work in the Thesis was based on two-dimensional calculations, assuming ring magnets. Further work is needed to evaluate the 3D effect and magnet segmentation.

The purpose of my thesis is to establish a simple thermal model for a Parker GVM 210-150P motor and a SEVCON Gen4 Size8 inverter. These models give temperature variations of critical components in the motor and the inverter. My thesis will help Georgia Tech's EcoCAR-3 team in understanding the physics behind thermal modeling and why thermal study is necessary. This work is a prerequisite for Software in the Loop (SIL) simulations or Hardware in the Loop (HIL) simulations for a hybrid electric vehicle.

The subject of the thesis is the investigation of the loss-mechanisms in high-speed permanent magnet disc generators. Such electrical machines can be directly coupled to gas turbine engines and run at speeds of up to 60000 revolutions per minute. The work focuses particularly on the losses occurring in the stator of the machine, which are: 1. Ohmic resistance losses 2. Eddy current losses 3. Circulating current losses 4. Pumping losses of coolant fluid Numerical modelling was used to gain a theoretical understanding of the loss-mechanisms involved. Validation of these results was carried out by means of experiments conducted on several purposely built test rigs. The results of the experiments were then correlated to the numerical solutions so that the prediction of the losses for different geometries can be obtained with a high degree of certainty. For the numerical analysis, commercial software was used for thermal and flow problems, but for the electro-magnetic problems a new computer code using the object oriented language C++ was developed. Besides this, the magnitude and relation of eddy-currents and circulating currents in Litz cables was investigated in depth by modelling the Litz cables macroscopic properties in detail, which allowed the investigation of the effect of the cable bundling configuration. It was shown that the design of these machines is always bound onto the operating conditions as the magnitude of the different losses do not allow the ideal combination of properties to be found for a range of load points but only for given operating point.

High speed permanent magnet machines have been widely adopted for their ability to achieve high power densities while also retaining high efficiencies. However, operation at high speeds introduce several design and analysis challenges which encompass electromagnetic, thermal and mechanical considerations. Arguably the most challenging aspect of high-speed machine design is the reliable prediction of losses in the machine, particularly if the influence of the converter is accounted for. This thesis is focussed on the design and loss modelling of high speed permanent magnet machines, with a particular emphasis on establishing a detailed understanding factors that result in the torque density of machines decreasing with increasing speed. The thesis reports on a systematic investigation to establish the variation of torque density and power density with machine speed by way of series of design studies for a 250kW surface-mounted permanent magnet. The torque density is shown to reduce with machine speed rating at different rates depending on the constraints applied. In several cases, an optimum speed for achieving maximum power density is observed, beyond which the power density begins to reduce. The thesis then considers in detail the influence of ripple currents generated from hysteresis closed loop control, on machine torque output and iron losses. A novel post-processing method is developed for iron loss calculation to accommodate with the large number of data points required to fully capture the effect of high frequency current ripple. A series of analytical derivations are developed to illustrate that high frequency iron losses due to switching are largely independent of the exact nature of the switching behaviour and governed by steady-state machine parameters. The rotor eddy current losses in rotor magnets and a metallic containment sleeve are then calculated, using a novel three-dimensional analytical model for field, current, and loss prediction. Good agreement is achieved between the analytical model and finite element simulations.

Pour respecter les contraintes sur l’efficacité pour une machine électrique, il est important de faire une évaluation précise des pertes. Dans le cas des machines à aimants permanents alimentées par un onduleur à MLI, le contenu harmonique haute fréquence lié à la modulation peut rajouter des pertes additionnelles dans la machine que les modèles classiques ont tendance à négliger. Le développement de nouveaux modèles de pertes qui tiennent compte des pertes additionnelles, va permettre d’améliorer des méthodes d’analyse et de conception de machines électriques. Dans ce travail de recherche, différentes méthodes pour estimer les pertes dans les machines synchrones à aimants permanents, y compris les pertes mécaniques, les pertes magnétiques et les pertes cuivre sont présentées. Une nouvelle expression pour estimer les pertes magnétiques dans les tôles en tenant compte de l’effet de peau généré par des courants harmoniques de haute fréquence est élaborée. Concernant les pertes d’hystérésis, un algorithme pour l’identification de cycles mineurs est présenté. Un autre modèle analytique pour l’estimation des pertes MLI dans le stator de la machine à aimants permanents et une nouvelle approche pour l’estimation directe des pertes par courant de Foucault dans les tôles par calcul de champ en 2D sont aussi développés. La méthodologie pour la conception d’une machine à aimants permanents montés en surface est brièvement décrite. Un prototype a été conçu et mise en oeuvre pour mesurer les pertes dans différentes conditions de fonctionnement et valider les modèles de pertes. Différents modèles pour les pertes magnétiques sont comparés afin de sélectionner la méthode la plus appropriée dans le domaine du temps ou de la fréquence. Cette méthode est ensuite validée pour un large éventail de conditions de fonctionnement. Les pertes dans deux rotors à aimants permanents (avec et sans segmentation des aimants) sont comparés. L’effet de la segmentation des aimants et le choix du matériel pour la culasse du rotor sont aussi analysés. Les résultats sont ensuite utilisés pour valider les performances d’un modèle analytique pour estimer les pertes par courant de Foucault dans les aimants permanents.
In order to respect the constraints for efficiency in an electrical machine, losses should be accurately estimated. In the case of a permanent magnet machine fed by a PWM supply, the high frequency harmonic content of the current (associated with the modulation scheme), may generate additional losses in the machine which the conventional models tend to overlook. Development of new models which may take account of these additional losses will allow us to improve the analysis and design of the electrical machines. In this work various models for the prediction of losses in a permanent magnet machine including the mechanical losses, copper losses and magnetic losses are presented. A new loss expression for taking account of the skin effect in a laminated magnetic material due to high frequency harmonic content of the stator current is developed. Regarding hysteresis losses, an algorithm for the identification of the minor hysteresis cycles is presented. An analytical model for the estimation of the PWM losses in the stator of the permanent magnet machine, and a new method for the direct estimation of eddy current losses in the lamination material by 2D-FE analysis are also developed. The design methodology for the design of a surface mounted permanent magnet machine is briefly described. A prototype machine is designed and realised to measure the losses in a variety of operating conditions and validate the loss models. Various models for magnetic losses are compared in order to find the most appropriate method in the time or frequency domains. The method which offers the best performance is then validated in a wide range of operating conditions. The losses in two PM rotors (with or without magnet segmentation) are compared and the effect of magnet segmentation and the choice of rotor yoke material are investigated by 2D FE analysis. These results are also used to evaluate the performance of an analytical model for the prediction of eddy current losses in the rotor magnets.

The study and the analysis of quench initiation and propagation is of paramount importance in the design of any superconducting magnets. Several disturbances such as ac losses, failures of the cryogenics or heat load may induce the quench initiation on a magnet and determine its irreversible transition to the normal state. Since the early days of magnet construction, the scientific community has devoted significant efforts in the study of quench. In the present work, numerical methodologies are presented and discussed for the analysis of electro-thermal stability, quench propagation and temperature margin on superconducting cables and coils. The proposed models are applied to the analysis of several superconducting magnets under development in different research groups in Europe (EU) and United States (US). The comparison of the numerical results with the experimental tests or with different computational approaches make the author confident about the applicability and reliability of the proposed modelling techniques.

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.

Energy management is a fundamental facility for humanity. At present, the awareness that renewable energy cannot satisfy the entire energy needs of the community and that traditional energy sources have a limited duration makes it imperative to address the problem of their careful and responsible use. Therefore, the need for an intelligent and functional use of energy has led the technical-scientific community to concentrate its efforts on the issues of sustainable development and energy savings. The electric drives industrial sector has suffered this influence in a visceral way. This sector plays a leading role in the industrial frame as it is one of the main consumers of electricity. Moreover, the topic of electrical drives design and optimization has become of considerable importance especially for the automotive sector and for hybrid and electric traction applications. In particular, in the last two decade, this sector has undergone a considerable technological development thanks to the exponential evolution of power electronics, the use of increasingly performing electric machines and new control techniques. In this scenario, the design and optimization of control algorithms for interior permanent magnet synchronous machines (IPMSM) has became of considerable interest in the scientific and technological community. In detail, the IPMSM is one of the most used electrical machine typologies in the electric traction applications due to the high efficiency and flux-weakening capability. The purpose of the research project “Realization of innovative algorithms for the minimization of the losses in synchronous brushless motors for automotive application” consists in the design and development of innovative Loss Model Algorithm (LMA) for interior permanent magnet synchronous machines (PMSM). The LMAs goal is the identification of the working points of the machine at minimum losses through the optimal determination of the control variables values. Therefore, the use of LMAs in electric drives can be of considerable utility in terms of energy savings especially for automotive application where energy autonomy is a crucial parameter. In detail, a LMA is a control algorithm based on the knowledge of the dynamic mathematical model of the IPMSM. Therefore, the performances of LMA are strictly dependent on the accuracy of the mathematical model and of its electrical and magnetic parameters. In this regard, the research carried out during the PhD course focused on the four macro topics, reported as chapters of the PhD thesis: 1. loss minimization control techniques for PMSM: state of art; 2. performances analysis of the power loss mathematical models; 3. efficiency measurement of electric drives equipped with interior permanent magnets synchronous machine (IPMSM); 4. enhanced mathematical modelling of IPMSM. The first chapter describes the state of art of main Loss Minimization control Algorithms (LMA) for electric drives equipped with PMSM. The LMAs can be classified into two general approaches named Search control and Loss Model Control, respectively. The main features of each approach are presented and discussed. Particular attention is devoted to the conventional IPMSM modelling approach employed in the LMC. Finally, the LMA chosen as a case of study is illustrated. The second chapter describes the performances analysis of the power loss mathematical models for LMC. In detail, the conventional IPMSM modelling approach and the IPMSM modelling approach that take into account the magnetic self-saturation effects and the variability the iron loss with the supply frequency are studied and discussed. In order to evaluate the performances of each modelling approach, several experimental investigations have been carried out on an electric drive equipped with an IPMSM. The third chapter is focused on the design and validation of accurate efficiency measurement approach for electrical drives equipped with IPMSMs. In particular, the efficiency measurement approaches for electrical drives described by the international standards and by the scientific literature are described and discussed. Particular attention was paid to the new standard IEC61800 and their prescriptions have been employed for the efficiency estimation of the electric drive under test. Finally, a new measurement approach for the comparison of the electrical drive efficiency, when it is controlled with several control algorithms, is presented and experimentally validate. The last chapter describes the enhanced mathematical modelling of IPMSM that take into account the magnetic saturation, cross-coupling, spatial harmonics and iron loss effects. This activity was carried out in collaboration with the Institute of Power Electronics System (ELSYS) of the ―Technische Hochschule Nürnberg Georg-Simon Ohm‖ during the PhD visiting period. In particular, the research activity was focused on the finite element modelization and analysis of IPMSMs and the Ansys Maxwell simulation environment (FE software) has been used for the simulation of the IPMSM under test. In detail, in order to define a high-fidelity IPMSM mathematical model, a large number of FEA investigations have been carried out. In this regard, the enhanced IPMSM mathematical model is described, implemented in Matlab®/Simulink environment and, for validation purpose, its performances have been compared with those of the IPMSM implemented in Ansys Maxwell environment.

In the first section, the magnetisation characteristics of the switched-reluctance motor are examined. Measurements have been carried out using both static and dynamic test methods. The test data has been compared with simulation results from analytical design programs and finite element models. The effects of mutual coupling on the magnetisation characteristics are investigated through measurement and simulation. Results show that the degree of mutual coupling is strongly dependent on the winding arrangement of the machine. In the next section, the difficulties in measuring the properties of permanent-magnet machines are discussed in detail, and solutions to common problems proposed. The measurement and analysis methods used for the switched-reluctance motor are further developed for analysis of permanent magnet machines. Techniques for determining the variation in synchronous reactances and permanent magnet flux are presented. Finite element simulations are used to show the variation of magnet flux under loading, a condition ignored in classical analysis methods. The final section discusses the analysis of magnetisation characteristics of electrical sheet steels. Comparison is made between measurements carried out on single sheet tester and Epstein square test rigs. The iron losses of a typical non-grain-orientated steel are measured under both sinusoidal and nonsinusoidal flux density conditions. The iron losses are shown to increase significantly when higher harmonic components are introduced to the flux density waveform. The difficulties in modelling the nonlinear iron loss characteristics of electrical steels are considered.

Дипломний проект містить: сторінок – 93, рисунків – 32, таблиць – 32 та графічну частину на 6 листах А1. Метою роботи є розробити алгоритм розрахунку параметрів електроприводу автомобіля на основі синхронного двигуна з постійними магнітами. В даній дисертації було розраховано параметри тягового двигуна, батареї та елементів кола керування електроприводом електромобіля. Синтезовано алгоритм керування синхронним двигуном з вбудованими постійними магнітами з мінімізацією втрат. Було досліджено динамічні характеристики електромеханічної системи методом математичного моделювання. Було порівняно енергоефективність розробленого методу керування зі звичайним векторним керуванням.
The thesis comprises: 93 pages, 32 figures, 32 tables, and graphical part on 6 pages A1. The thesis aims to develop the method of calculating the parameters of the electric vehicle drivetrain, based on a permanent magnet synchronous motor. Parameters of traction motor, battery pack, and control circuit elements of the electric vehicle drivetrain were calculated. Loss minimization control algorithm for interior permanent magnet synchronous motor was developed. Electromechanical system performance characteristics were studied by mathematical simulation. The efficiency of the developed control algorithm was compared with the conventional vector control method.

Thesis (PhD (Electrical and Electronic Engineering))--University of Stellenbosch, 2010.
ENGLISH ABSTRACT: Certain types of electric machines are particularly susceptible to the proliferation of eddy currents flowing within the solid conducting regions in the rotor. Single-layer, non-overlapping windings within uneven open slots are some stator properties that can produce damaging, asynchronous magnetic field harmonics which manifest in the rotor as eddy currents. The ohmic losses caused by these eddy currents are a source of inefficiency and can cause a marked increase in the temperature of the rotor. This temperature rise can be dangerous for the magnets, which have to be kept within temperature limits to avoid partial or full demagnetization. The research work presented here is concerned with reducing the effect of eddy currents in the rotor magnets and solid rotor yoke of an electric machine. The work presents analytical methods to calculate the magnetic fields, eddy currents and solid loss in an electric machine due to current in the winding and due to the interaction of the permeance variation in the stator with the magnets in the rotor. A method is also suggested where the analytical theory can be used with a magnetostatic finite element solution to produce a transient solid loss result. The research work also investigates a method for optimal segmentation in both level and penetration, and provides some design suggestions. The work presents the method of partial magnet segmentation, which is a technique whereby thin incisions are made into the magnet material from one or both sides. Another method of partial rotor segmentation is also presented where the incisions are made into a portion of the magnet-facing solid yoke. These methods attempt to interrupt the flow of eddy currents and increase the resistance ‘seen’ by the eddy currents, while also keeping construction difficulty and cost to a minimum. The methods are verified using finite element calculations which are compared to measured results. The result is that partial magnet segmentation is a very useful, effective and practical method of segmenting magnets. The loss reduction profile can be similar to that of traditional full segmentation. The method of partial rotor segmentation also shows a large reduction in rotor power loss. With implementation of these methods on a test machine, one can expect an efficiency increase of more than 4 %
AFRIKAANSE OPSOMMING: Sekere tipes van elektriese masjiene is veral sensitief vir die vloei van werwelstrome in solied geleidende gebiede in die rotor. Enkellaag, nie-oorvleuelende wikkelings in oneweredige oop gleuwe is enkele stator eienskappe wat skadelike, asinchrone magneetveld harmonieke tot gevolg kan hê, wat as werwelstrome in die rotor manifesteer. Die ohmiese verliese wat deur hierdie werwelstrome teweeg gebring word is 'n bron van ondoeltreffendheid en kan lei tot 'n merkbare toename in die temperatuur van die rotor. Hierdie temperatuur styging hou gevaar in vir die magnete en moet binne temperatuur limiete gehou word om gedeeltlike of self volle demagnetisering te vermy. Die navorsing vervat in hierdie document is gemoeid met die vermindering van die effek van werwelstrome in die rotor magnete en in die soliede rotor juk van 'n elektriese masjien. Die werk bied analitiese metodes aan vir die berekening van die magneetvelde, werwelstrome en soliede verliese in ’n elektriese masjien as gevolg van strome in die wikkelings en die interaksie van die permeansie variasie van die stator met die magnete in die rotor. ’n Metode word ook voorgestel waar die analitiese teorie saam met ’n magnetostatiese eindige element oplossing gebruik word om ’n resultaat vir die oorgang soliede verliese te verkry. Die navorsingswerk ondersoek ook ’n metode vir die optimale segmentering in beide vlak sowel as penetrasie, en verskaf sekere ontwerp voorstelle. Die werk bied die metode aan van gedeeltelike magneet segmentering, wat 'n tegniek is waarvolgens dun insnydings gemaak word aan een of beide kante van die magneet materiaal. Nog ’n metode van gedeeltelike rotor segmentering word beskou waar die insnydings in in ’n gedeelte aan die magneetkant van die soliede rotor juk gemaak word. Hierdie metodes poog om die vloei van werwelstrome te onderbreek en die weerstand soos "gesien" deur die werwelstrome te verhoog, terwyl konstruksie kompleksiteit en koste tot ’n minimum beperk word. Die metodes word bevestig deur eindige element berekeninge wat met gemete resultate vergelyk word. Die gevolg is dat gedeeltelike magneet segmentering 'n baie nuttige, doeltreffende en praktiese metode van die segmentering van magnete is. Die verliesverminderingsprofiel van gedeeltelike segmentering kan soortgelyk wees aan dit van tradisionele volle segmentering. Die metode van gedeeltelike rotor segmentering toon ook 'n groot afname in rotor drywingsverlies. Met die implementering van hierdie metodes op ’n toetsmasjien, kan ’n mens ’n verhoging in benuttingsgraad verwag van meer as 4 %

In recent times, researchers show a growing interest in the control of permanent magnet synchronous motor, which is superior to conventional induction motor in several performance and efficiency aspects. Particular attention is given to the brushless dc motor (BLDC), as it is gaining popularity in low to medium power applications including adjustable speed drive and electric vehicle. Most works pertaining to BLDC control focus on dynamic performance improvement. However, limited works have been reported for BLDC efficiency optimisation. From an energy perspective, maximum efficiency operation is desired, as energy saving closely ties to the operating capacity and thermal dissipation, particularly for battery powered systems. This dissertation presents a comprehensive motor modelling and analytical power loss modelling in the Matlab/Simulink environment that account for major loss mechanisms in a three phase inverter-fed BLDC motor through closed form equations. To explore the change in motor power losses under variable current excitation, two well-known current excitation schemes, namely sinusoidal and square current excitations, have been implemented to facilitate comparison of efficiencies of the resulting motor operations. Key power loss components are identified and examined, for both current excitation schemes, under the context of variable motor operating speed. The closed-loop system model is simulated under MATLAB/Simulink environment. Power losses under two current excitation schemes are investigated across different speed regions under nominal load. The complete motor drive has been experimentally implemented using digital signal processor based control board for a low power BLDC. The experimental results validate the higher efficiency due to sinusoidal current excitation across a wide speed region, compared to square wave current excitation. The resulting work contributes methodologically to the broader problem of efficiency optimising control.

The aim of this thesis is to design a kilowatt three-phase step-down rotary transformer for a permanent magnet DC motor. The permanent magnet DC motor has an on-rotor drive system, and therefore requiring a power supply that can transfer power to its drive unit without mechanical contact. The rotary transformer has a detached magnetic coupling structure that qualifies it as a potential method for the wireless power transfer. This thesis studies the rotary transformer as a static device, focusing on its core loss. By using a transient finite element analysis of COMSOL Multiphysics and an iron loss prediction model, the rotary transformer was optimized in terms of efficiency and power density for the on-rotor drive system through proper material selection and geometry exploration. After this, a mechanical design, which based on a literature review of the influences of manufacturing processes on electrical steels, was proposed for realizing the core fabrication and the rotary transformer assembly. The results show that the rotary transformer can step down 400 V/50 Hz three-phase voltage to 13.15V in a Delta-wye connection and output 1.17kW power over an air-gap of 0.3mm with 95.94% overall efficiency. The proposed mechanical design enables the transformer to minimize the core loss and the manufacturing cost. Without using resonant inductive coupling, this transformer design simplifies the power supply for the motor, thereby decreasing the motor manufacturing and maintenance cost.

This master´s thesis deals with permanent magnet synchronous motor, which is part of hybrid system of Toyota Prius. You can find study of this motor in program FEMM in this thesis. Model of equivalent magnetic circuit and magnetic flux density are part of this work. There is also information about core losses.

Les tokamaks visent à produire de l'énergie par fusion thermonucléaire en chauffant un plasma d'hydrogène jusqu'à 150 millions K et en le confinant à l’aide d’un champ magnétique intense créé par des aimants transportant d’importants courants. La supraconductivité est un atout précieux ici car permettant de réduire la taille des aimants et leur consommation énergétique en contrepartie d’un refroidissement cryogénique. Cependant, dans les tokamaks, des variations de champ magnétique apparaissent (ex : décharge du solénoïde central) et génèrent des pertes par induction dans les aimants. Si leur température augmente trop, ils peuvent perdre leur état supraconducteur lors d’une transition brutale appelée "quench": afin de les protéger, ils sont déchargés de leur courant entraînant ainsi la perte du plasma. Nous avons concentré notre travail sur la modélisation de ces pertes car leur connaissance est cruciale pour le bon dimensionnement du refroidissement des aimants et la prédiction des limites opérationnelles du tokamak. Afin d'améliorer la compréhension physique de ce phénomène complexe et de proposer des solutions simples mais réalistes, facilement intégrables dans des plateformes multiphysiques déjà fortement sollicitées par la modélisation d'autres effets, nous avons choisi d'adopter une approche analytique. Les câbles présents dans les tokamaks ayant une architecture assez complexe (centaines de brins torsadés ensemble), nous avons mené des études analytiques et expérimentales aux différentes échelles du câble; nous comparons ensuite les résultats de notre approche à ceux d'autres modèles existants (ex : numériques) et, lorsque cela est possible, à l'expérience
Tokamaks aim at producing energy by thermonuclear fusion heating a hydrogen plasma up to 150 million K and confining it with an intense magnetic field created by magnets carrying important currents. Superconductivity is a very valuable asset in this field since it allows to reduce the size of the magnets and their energy consumption in exchange for cooling them down to cryogenic temperatures. However, in tokamaks, magnetic field variations occur (e.g. due to the central solenoid discharge) and generate induction losses in the magnets. If their temperature increases too much, they lose their superconducting properties in a brutal transition called "quench": to protect their integrity, they are then discharged and the magnetic confinement of the plasma is lost. We have therefore focused on the modeling of these losses - more precisely on the “coupling losses” - since their knowledge is crucial to safely adapt the cryogenic cooling of the magnets and predict the operating limits of the tokamak. In order to both enhance the physical understanding of this complex phenomenon and provide simple but realistic solutions that can easily be integrated in multiphysics platforms already heavily solicited by the modeling of other effects, we have chosen to adopt an analytical approach on this problem. The cables commonly considered for tokamaks presenting a rather complex architecture (several hundreds of strands twisted together in specific patterns), we have carried out analytical and experimental studies at the different scales of the cable; we then compare the results of our approach to other existing ones (e.g. numerical models) and, when possible, to the experiment

There is an increasing interest in using new composite materials in microwave devices, to reduce size and weight while maintaining similar performances. A new promising material group is named magneto-dielectric materials, which have the permittivity and permeability values both larger than one. Compared to the commercially used dielectric materials, magneto-dielectric materials can achieve a larger miniaturization factor with the equivalent properties as dielectric materials. There is a very limited availability of commercial magneto-dielectric materials. A recent addition was from Rogers Corporation with MAGTREX 555, [1], that is available as a printed circuit board laminate. The material is limited to 500 MHz operational frequency due to its increased magnetic and dielectric losses. In this thesis the purpose is to understand the loss mechanisms, characterize and understand the state-of-the-art magneto-dielectric materials at microwaves, and to produce a magneto-dielectric material in the lab to understand the material better. A new material was developed with magneto-dielectric properties. The material was based on a polymer base of polystyrene that serves as a dielectric material and doped with nickel nanoparticles that produce the magnetic properties. The contents of the nanoparticles in the mix is a design variable. Nickel-polystyrene samples with different nickel contents of 0%, 2.3% and 4.5%, were produced in the lab and measured in-house to understand the loss mechanism and RF performance.

As the major electricity consumer, electrical machines play a key role for global energy savings. Machine manufacturers put considerable efforts into the development of more efficient electrical machines for loss reduction and higher power density achievements. A consolidated knowledge of the occurring losses in electrical machines is a basic requirement for efficiency improvements. This thesis deals with iron losses in electrical machines. The major focus is on the influences of the stator core magnetic material due to the machine manufacturing process, temperature influences, and the impact of inverter operation. The first part of the thesis gives an overview of typical losses in electrical machines, with focus put on iron losses. Typical models for predicting iron losses in magnetic materials are presented in a comprehensive literature study. A broad comparison of magnetic materials and the introduction of a new material selection tool conclude this part. Next to the typically used silicon-iron lamination alloys for electrical machines, this thesis investigates also cobalt-iron and nickel-iron lamination sheets. These materials have superior magnetic properties in terms of saturation magnetization and hysteresis losses compared to silicon-iron alloys. The second and major part of the thesis introduces the developed measurement system of this project and presents experimental iron loss investigations. Influences due to machine manufacturing changes are studied, including punching, stacking and welding effects. Furthermore, the effect of pulse-width modulation schemes on the iron losses and machine performance is examined experimentally and with finite-element method simulations. For nickel-iron lamination sheets, a special focus is put on the temperature dependency, since the magnetic characteristics and iron losses change considerably with increasing temperature. Furthermore, thermal stress-relief processes (annealing) are examined for cobalt-iron and nickel-iron alloys by magnetic measurements and microscopic analysis. A thermal method for local iron loss measurements is presented in the last part of the thesis, together with experimental validation on an outer-rotor permanent magnet synchronous machine.

QC 20140516

Práce se zabývá výpočty magnetických a tepelných vlastností servomotoru s permanentními magnety (motor M718 I vyráběný firmou VUES s.r.o. v Brně). Všechny uvedené výpočty jsou založené na numerických metodách konečných prvků a konečných objemů. 2D magnetická analýza motoru byla řešena s pomocí programu FEMM, zatímco pro 3D analýzu byl využit software ANSOFT. Magnetické analýzy umožnily stanovit rozložení magnetického pole v motoru a ve vzduchové mezeře. Ztráty způsobené vířivými proudy byly počítány v závislosti na rozměrech permanentních magnetů a velikosti toku magnetické indukce ve vzduchové mezeře. U 3D modelu v programu ANSOFT byly vypočítány i Joulovy ztráty. Pro daný servomotor byly navrženy dva způsoby chlazení. V prvním případě se jedná o vnitřní chladicí systém. K původnímu modelu motoru byly přidány některé modifikace (otvory v rámu motoru a radiální ventilátor na hřídeli uvnitř rámu motoru). U druhého způsobu chlazení bylo navrženo vnější chlazení. K původnímu rámu byly přidána chladicí žebra a radiální ventilátor na hřídeli vně rámu motoru. Výpočty proudění a tepelná analýza byly provedeny jak pro původní model motoru, tak i pro modifikovaný návrh (vnitřní a vnější chlazení) pomocí software ANSYS Workbench. Teplotní charakteristiky původního motoru byly měřeny různými senzory. Bylo provedeno porovnání experimentálně získaných výsledků s vypočteným teplotním modelem. Práce byla vytvořena v rámci doktorského studijního programu Elektrotechnika a komunikační technologie, obor Silnoproudá elektrotechnika a elektroenergetika. Podstatná část práce vznikla za podpory Centra výzkumu a využití obnovitelných zdrojů energie a výzkumných projektů CZ.1.05/2.1.00/01.0014 and FEKT S-11-9.

La stima delle perdite rotoriche per correnti parassite (Eddy currents) è cruciale nella progettazione dei moderni motori SPM. Poichè le loro prestazioni dipendono fortemente da esse. I motori devo essere progettati in modo da prevenire eccessive perdite rotoriche, le quali possono portare alla demagnetizzazione dei magneti e ad un deterioramento delle performance generali della macchina. Nel capitolo 1 sono illustati i principi fisici che descrivono il comportamento dei motori elettrici e delle perdite rotoriche per correnti parassite. Sono poi discusse le proprietà dei materiali impiegati nell'ambito della costruzione di macchine elettriche ed infine sono presentate le tecniche al momento più diffuse per la stima delle correnti parassite. Dopo di che nel capitolo 2 è analizzato un modello semplificato di un SPM, in cui il rotore è sostituito con un cilindro solido. In particolare è stata investigata la dipendenza dalla resistività del materiale impiegato per il rotore. Una tecnica basata sul current sheet per la stima delle perdite rotoriche è presentata in dettaglio e implementata. Infine è riportata la validazione della procedura basata sul current sheet. Nel capitolo 3 l'analisi è estesa a un reale motore SPM, in particolare sono investigate le perdite nei magneti. Sono quindi illustrate le criticità di tale analisi e i limiti del modello. Per finire nel capitolo 4 sono riportati i risultati dei test effettuati, e sono discussi possibili futuri sviluppi del metodo illustrato.

Thesis (Ph. D.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2004.
Habetler, Thomas, Committee Member ; Sadegh Nader, Committee Member ; Taylor David, Committee Member ; Tsiotras Panagiotis, Committee Co-Chair ; Heck-Ferri Bonnie, Committee Co-Chair. Vita. Includes bibliographical references (leaves 319-326).

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 deals with the analysis of magnetic losses in electrical machines and the possibilities of their measurement. Magnetically soft and hard materials are very prone to changing magnetic properties. They can be changed simply by changing the temperature of the material or different stresses induced in the material, resulting in different results. These changes are important to keep in mind when an electric machine is being designed. The original parameters of the affected materials can be restored by annealing or grinding. These methods release the induced stresses within the material. Due to these effects, it is also important to know how to measure magnetic parameters. Each way has its own specifics and has a certain error of the measurement. When the machines for higher efficiency, rpm or higher temperatures are designed, it is advisable to know how their magnetic properties changed. This thesis deals with the properties of different materials, their measurements and finally simulation of the chosen electric machine with the application of the measured results.

This thesis project will evaluate which kind of electrical motor is best suited for aircraft propulsion and which parameters effect the efficiency. An economic analysis was conducted, comparing the fuel price (Jet A1) for a gas turbine and the electricity price for an electric motor of 1MW. The study was conducted by using analytical methods in MATLAB. Excel was used to compile and present the data. The data used in this thesis project were assumed with regards to similar studies or pre-determined values. The main losses for the Permanent Magnet Synchronous Motor (PMSM) were calculated to achieve a deeper understanding of the most important parameters and how these parameters need to improve to allow for future electric propulsion systems. The crucial parameters for the losses were concluded to be the temperature, voltage level, electrical frequency, magnetic flux density, size of the rotor and rotational speed. The three main losses of a PMSM was illustrated through the analytical equations used in MATLAB. The calculations present how the ohmic losses depend on the temperature (0-230°C) at different voltages (700V and 1000V), how the core losses depend on frequency (0-1000Hz) at different magnetic flux densities and how the windage losses depend on rotational speed (7000-10000 rpm). It could be concluded that at 8500 rpm an efficiency of 91,26% could be achieved at 700V, 1.5T and 90.4% at 1000V, 1.65T. The decrease in efficiency is a result of the increase in magnetic flux density. When looking at the economic viability of electrical integration the power to weight ratio and energy price was compared for the gas turbine and electrical motor including an inverter and battery. This resulted in a conclusion that a pure electrical system may not compete with a gas turbine in 30 years of time due to the low energy density of the battery. It was also concluded that the emissions during cruise could be lowered significantly. If the batteries were charged in Sweden the emissions would decrease from ~937 kg CO2 to ~31 kg CO2. If the batteries were charged in the Nordic region the emissions would decrease to ~119kg CO2. However, if the batteries were to be charged in the US the carbon dioxide emission would be ~1084 kg CO2, which is an increase in CO2 emission compared to the gas turbine.

Flywheel energy storage units have become a viable alternative to electrochemical batteries in applications such as satellites, uninterrupted power supplies, and hybrid vehicles. However, this performance is contingent upon safe operation since these flywheels can release their stored energy almost instantaneously upon failure. The research presented here investigates a health monitoring technology that may give an early indication of degraded material properties in a concentric ring composite flywheel. The existence of degraded material properties is manifested as a change in mass eccentricity due to asymmetric growth of the outermost flywheel ring. A test rig concept to investigate the technology is developed in detail using a systems engineering design process. Successful detection of the change in mass eccentricity was verified analytically through dynamic modeling of the flywheel rotor and magnetic suspension system. During steady state operation detection was determined to be feasible via measurements of the magnetic bearing currents and shaft position provided by the magnetic suspension feedback sensors. A rotordynamic analysis was also conducted and predicts successful operation to the maximum operating speed of 50,000 Rpm.

Observamos neste trabalho o processo de mudança de estrutura fina em colisões entre átomos de 85Rb resfriados e aprisionados em uma armadilha magneto-óptica. Medimos, através da fotoionização de fragmentos atômicos gerados nessas colisões, as taxas segundo as quais os átomos deixam a armadilha induzidos por esse processo colisional. Realizamos estudos das taxas de perda com relação a intensidade do laser de aprisionamento e com a freqüência, utilizando para isso a técnica de catálise. Nossos resultados indicam que a contribuição do processo de mudança de estrutura fina para a taxa de perdas total não é dominante. Constatamos que a estrutura hiperfina desempenha um papel importante na dinâmica colisional e na determinação dos valores das taxas. Interpretamos nossos resultados através de um modelo semi-clássico, sendo que este foi incapaz de explicar todos os efeitos observados. Propusemos algumas explicações qualitativas para as discrepâncias observadas. Acreditamos que nossos resultados devam servir de estímulo para novos trabalhos teóricos nesta área.
We report the observation of trap-loss collisional rates due to fine structure changing collisions between cold and trapped 85Rb atoms. We have measured, by photoionization of the atomic fragments in 5P1/2 state originated in these collisions, the rates through the atoms leave the trap induced by this loss mechanism. We carried out experiments to determine the rate dependence with the intensity of the trapping laser, and with the frequency, using the catalisys technique. We also measured the contribution of this process to the total trap-loss rate and determined that fine structure changing is not the dominant loss mechanism. It was also observed that the hyperfine structure plays an important role in the rate behavior. We compared our results with those given by a semiclassical theoretical approach, the Gallagher-Pritchard model, and some disagreements were observed. We proposed some arguments to explain these discrepancies. We believe that such results should stimulate theoretical work on this field.

Permanent magnets play a key role as a component in a wide range of devices utilised by many industries; they are widely used in several electromechanical applications to convert energy, including actuators, motors and sensors, home appliances, office automation equipment, speakers, aerospace, wind generators and more. Traditionally the adopted PMs were obtained from Rare Earth components, such as NdFeB, with high magnetic performance, but expensive. The research of alternative permanent magnets, in many cases has brought to choose the ferrites, mainly due to their low cost, but sometimes with significant design modifications of the final circuit, and possible increment of the weight. Permanent magnets can roughly be divided into two categories: sintered (metallic) and bonded, these last representing a valid alternative to the first. Bonded magnets consist of two components: a hard magnetic powder and a non-magnetic binder; the powder may be hard ferrite, NdFeB, SmCo, and is mixed with binders for compression or injection moulding. The benefits lie in the adoption of polymeric binders to prepare the magnetic mixture: the resulting magnetic characteristic can be then “tuned” by adopting different percentages of the plastic binder. Moreover, the realisation process is simpler and cheaper than that of sintered materials, and no special protective treatment is needed. The majority of the magnetic circuits are made with soft magnetic materials. Commonly laminated steels are adopted but recently the use of Soft Magnetic Composite (SMC) materials has increased representing a new solution to design the electrical machines with respect to traditional electrical steels. SMC materials are realized with pure Iron grains coated and insulated by means of a layer that should be organic or inorganic. With respect to traditional laminated steel, these materials present different advantages: the capability to lead the magnetic flux in all directions, the volume reduction, the possibility to realize components with new complex shapes and geometries, and the reduction of iron losses, mainly the eddy currents, at medium and high frequency. On the other hand, the mechanical performances, in terms of strength, are in general weak. Furthermore, a new material typology is introduced: the Hybrid Magnetic Composites (HMC), which are obtained with a combination of soft and hard magnetic materials mixed with a binder. The basic idea is that such materials should reflect the performance of AlNiCo magnets, low coercivity and adequate remanence, typically used in sensors applications. Prototypes of traditional and unconventional rotating machines, such as assisted reluctance motors, brushless DC motors, axial flux machines and electromechanical frequency converters, have been studied in own laboratories and tested to evaluate the results coming from the adoption of the proposed materials in substitution of the commonly adopted (and expensive) Rare Earth sintered magnets. Different type of electrical machines can adopt innovative magnetic materials with the aim to improve their performance. Induction motors are very useful and robust machines; on the other hand, such type of machines does not have a high dynamic behaviour. The DC motors can be easily controlled, but the presence of the brushes causes limitations on the efficiency, thermal restrictions and reduced life. The axial flux motors (AFM) have high efficiencies but the construction of the machines is very complex. The synchronous reluctance machines (SRM) have a lower cost compared to brushless ones. In general, the reluctance electrical machines don’t use permanent magnets. In this way, they have a reduction in the costs and allow a high overload capability. On the other hand, the lower power factor and power density, compared to PM synchronous motor (PMSM), are the main disadvantages. The filling of flux barriers with the permanent magnets allows the overcoming of these drawbacks. However, the regular ferrite and NdFeB sintered magnets cannot fill the flux barriers with complex geometries. For this reason, the use of bonded magnets can be a solution for a better utilization and design of flux barriers. Therefore different prototypes have been prepared and analyzed in our laboratories using SMC materials. Several experiments have been performed using dedicated test benches, where magnetic, energetic and mechanical aspects have been considered. On the other hand, with regard to HMCs, various magnets have been made in our laboratories, and different properties have been investigated: the effect of Iron content in the material and, also the binder content effect has been analysed.

The core used to build power inductors and transformers are soft magnetic materials. When there is alternating external field, the magnetic moments rotate and consume energy, which is the core loss. The core loss depends on the AC flux frequency, amplitude, waveform, DC bias and temperature. These dependences are nonlinear and difficult to predict. How to measure, model and analyze the core loss is a challenge for decades.
In this dissertation, two new core loss measurement methods are introduced first. These two methods use the reactive cancellation concept to reduce the sensitivity to phase discrepancy, which will destroy the accuracy in classic two-winding method for high frequency high quality factor sample measurements. By using the new measurement techniques the accuracy can be improved by several orders. The first is for sinusoidal waveforms, and the second is for non-sinusoidal wave. The new methods enable high frequency core loss characterization capability, which will help scientists and engineers on material research and inductor/transformer design. Measurement examples, considerations and error analysis are demonstrated and discussed in detail.
With the measurement techniques, the core loss under rectangular AC voltage and DC bias current are investigated. A new core loss model named rectangular extension Steinmetz equation (RESE) is proposed based on the measurement results. The new model is shown to be more accurate than the existing core loss models. Several commercially available MnZn ferrites are characterized and modeled.
Other than conventional MnZn ferrite materials, three commercial LTCC ferrite materials are characterized for integrated power supply applications. Based on characterized properties of these LTCCs, a group of new LTCC ferrites are fabricated and tested. The new LTCC is fabricated by laminating commercial LTCC tapes and co-firing. The new LTCC is demonstrated to have over 50% more inductance over the commercial LTCC materials. This work indicates that the power electronics engineers should work with material engineers to get the optimum material for a given application.
In the last part, the core loss of the partially saturated lateral flux planar inductor is analyzed. The challenge of the analysis is the complexity of the distribution of bias field and flux density in a highly biased planar inductor. Each point in the core is working at different excitation and bias condition, and the core loss density is very non-uniform. The proposed method combines the characterization tested in previous chapters and the commercial finite element tool. Experiments verified that the calculation errors are within about 10%.
In conclusion, the research in this dissertation proposed a complete solution to measure, model and analyze the high frequency core loss. This solution will not only facilitate fundamental research on physics understanding and material innovation, but also development of power electronics and RF applications.

Ph. D.

In order to design a power transformer it is important to understand its internal electromagnetic behaviour. That can be obtained by measurements on physical transformers, analytical expressions and computer simulations. One benefit with simulations is that the transformer can be studied before it is built physically and that the consequences of changing dimensions and parameters easily can be tested.

In this thesis a time-domain transformer model is presented. The model includes core losses as magnetic static hysteresis, eddy current and excess eddy current losses. Moreover, the model comprises winding losses including eddy currents, capacitive effects and leakage flux. The core and windings are first modelled separately and then connected together in a total transformer model. This results in a detailed transformer model.

One important result of the thesis is the possibility to simulate dynamic hysteresis including the eddy current shielding in the magnetic core material. This is achieved by using Cauer circuit combined with analytical expression for static and dynamic hysteresis. Thereby, all magnetic loss components in the material can be simulated accurately. This dynamic hysteresis model is verified through experiments showing very good agreement.

The main goal of this thesis is a determination of an idle stray losses in induction machine and creation calculation program in MATLAB. The stray losses are caused especially by the eddy currents on the surface of stator and rotor, further by a pulsation of these currents owing to the periodical change of air-gap permeance, magnetic induction in stator and rotor teeth and a differential leakage. Value of stray losses are different of engine construction especially by it are scoring insulated, uninsulated, straight or slant.

The dissertation thesis deal with the design and the optimization of the permanent magnet synchronous machine (SMPM) based on the artificial intelligence. The main target is to apply potential optimization methods on the design procedure of the machine and evaluate the effectiveness of optimization and the optimization usefulness. In general, the optimization of the material properties (NdFeB or SmCo), the efficiency maximization with given nominal input parameters, the cogging torque elimination are proposed. Moreover, the magnet shape optimization, shape of the air gap and the shape of slots were also performed. The well known Genetic algorithm and Self-Organizing migrating algorithm produced in Czech were presented and applied on the particular optimization issues. The basic principles (iterations) and definitions (penalty function and cost function) of proposed algorithms are demonstrated on the examples. The results of the vibration generator optimization (VG) with given power 7mW (0.1g acceleration) and the results of the SMPM 1,1kW (6 krpm) optimization are practically evaluated in the collaboration with industry. Proposed methods are useful for the optimization of PM machines and they are further theoretically applied on the low speed machine (10 krpm) optimization and high speed machine (120 krpm) optimization.

The scope of the present doctoral thesis has been the conception of a novel and efficient method for decelerating, over a range of frequencies, and completely 'stopping' light (zero group velocity, vg = 0) inside solid-state materials, at room temperature. To this end, we analytically show that an adiabatically tapered waveguide having a core of a lossless negative refractive index (NRI) metamaterial (MM) and claddings made of normal dielectrics can 'trap' a light pulse in such a way that each individual frequency component of the pulse is stopped at a different point along the waveguide, forming what we have called a 'trapped rainbow'. Crucially, it is shown that light can efficiently be in-coupled inside such a waveguide heterostructure from a normal dielectric waveguide, since with a suitable design one can achieve simultaneous thickness-, mode- and characteristic-impedance-matching between the two waveguides. A pertinent analysis reveals that the optical path length of a 'trapped' light ray (associated with a particular frequency component of the pulse), as well as the corresponding effective thickness of the NRI waveguide itself, become exactly zero. The ray circulates at the point where it is trapped in such a way that its trajectory forms what we have called (in view of its characteristic hourglass form) an 'optical clepsydra'. Furthermore, we introduce a novel methodology that allows for obtaining ultra- low- or zero-loss magnetic metamaterials over a continuous range of frequencies. We analytically prove that a higher-degrees-of-freedom MM design methodology based on equivalent electrical circuits with more than one mesh leads to metamaterial magnetism with either ultra-high figures-of-merit or with perfectly lossless performance over a broad range of frequencies. The so-obtained lossless metamaterial magnetism has a truly intrinsic character, and as such is scalable and can be implemented at any frequency regime, from the radio up to the optical domain.