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Dissertationen zum Thema „Electromagnetic calculation“
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1
Manolatou, Christina. „Calculation of effective electromagnetic parameters of helix loaded composites“. Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/36970.
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Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1995.Includes bibliographical references (p. 101-104).
by Christina Manolatou.
M.S.
2
Xu, Xiaoming. „New approximations in finite element calculation in high frequency“. Thesis, London South Bank University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.245127.
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3
Sargeant, Adam J. „Systematic semiclassical calculation of Coulomb excitation observables“. Thesis, University of Surrey, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.244783.
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4
Irenji, Neamat Taghizadeh. „Calculation of electromagnetic rotor losses in high-speed permanent magnet machines“. Thesis, University of Southampton, 1998. https://eprints.soton.ac.uk/47948/.
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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.
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Ati, Modafar K. „Calculation of electromagnetic field problems in large electrical machines using the finite element method“. Thesis, University of Newcastle Upon Tyne, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.238937.
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6
Mackenzie, Anne I. Rao S. M. „Paired pulse basis functions and triangular patch modeling for the method of moments calculation of electromagnetic scattering from three-dimensional, arbitrarily-shaped bodies“. Auburn, Ala., 2008. http://hdl.handle.net/10415/1447.
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7
Simonazzi, Mattia. „Misalignment tolerant model and force calculation in a resonator array for inductive power transfer“. Master's thesis, Alma Mater Studiorum - Università di Bologna, 2019. http://amslaurea.unibo.it/18981/.
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In this work, an inductive power transfer (IPT) system composed of an array of multiple magnetically coupled resonant inductors (cells) has been considered, allowing the transmission distance to be increased or the misalignment between the emitter and receiver coils to be considered. The analysis of the arrays can be carried out with the theory of magnetoinductive waves (MIW) or with circuit theory; the latter approach has been followed. The impedance matrix of the resonator array has been modelled for different receiver shapes and dimensions. Moreover, it has been expressed as a function of the space improving the accuracy of the model. The model has been exploited to calculate all the currents and voltages of the system. In first approximation, only the displacement in the MIW propagation direction has been considered, whereas the contribution of the receiver is expressed as a defect and becomes a function of the space as the mutual inductances between the circuits vary according to the receiver position. The self- and mutual inductance coefficients have been evaluated for each circuit of the system by applying the partial inductance method, whose formulas have been implemented in Matlab environment. These results have been validated by means of magnetostatic FEM analysis of the system using a commercial software. Experimental measurements on a prototype of a 1-D resonator array have been performed, confirming the calculated values of the currents and as a consequence, of the mutual inductances. The last part of the thesis is devoted to the calculation of the mechanical forces of electromagnetic origin experienced by the receiver over the array, as a result of the interaction between the whole magnetic field - generated by all the array cells - and the current circulating in the receiver. These forces have been theoretically discussed first, with a subsequent implementation of the calculation in Matlab environment and analysis of the obtained results.
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Bendz, Jon Eskil. „Modelagem, simulação, e visualização imersiva de redes sem fio“. Universidade de São Paulo, 2008. http://www.teses.usp.br/teses/disponiveis/3/3142/tde-30092008-144928/.
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Visualizações imersivas são muito valiosas para melhorar a compreensão de uma variedade de fenômenos físicos, que podem ser eventualmente modelados na forma discreta e simulados por computador. Dentre possíveis aplicações podemos utilizar a visualização imersiva como ferramenta pedagógica para percepção aumentada de tópicos complexos, ou como uma poderosa ferramenta de apoio analítico para ajudar os engenheiros a interpretarem os resultados de projetos. Este projeto de pesquisa aborda o uso da visualização imersiva de campos eletromagnéticos, especificamente os campos gerados por redes sem fio, largamente utilizadas no cotidiano como é o caso das redes IEEE 802.11 (Wi-Fi). Para tanto este trabalho propõe métodos novos para visualizar, em tres dimensões, campos eletromagnéticos variantes no tempo e distribuições de parâmetros interessantes relacionados a redes sem fio. Para atingir este objetivo, uma versão aprimorada do método de diferenças finitas no domínio do tempo (FDTD) é desenvolvido: o método FDTD de alta ordem e malha grosseira (Coarse Grid Higher Order FDTD, CGHO-FDTD). Portanto, soluções numéricas muito precisas, mais rápidas, e computacionalmente mais eficientes das equações de Maxwell podem ser obtidas. Os cálculos numéricos podem ser ainda mais rápidos pelo uso de computação paralela em um aglomerado de computadores. As características de domínio de tempo facilitam a criação de instantâneos de campos eletromagnéticos que estão se propagando, e desta maneira é possível criar figuras e animações tridimensionais que podem ser usadas para explicar alguns dos seguintes fenômenos físicos comuns em redes sem fio: difração, reflexão, e atenuação. Para que aumente a percepção física ainda mais, visualizações imersivas são feitas em um ambiente de realidade virtual. Por fim, a ferramenta desenvolvida também pode ser usada para criar distribuições muito detalhadas de parâmetros importantes que afetam o desempenho em uma rede sem fio. É mostrado que simulações de um ambiente fechado para prever a distribuição de potência de uma rede sem fio do tipo IEEE 802.11 (Wi-Fi), estão de acordo com as medidas.Immersive visualizations are very valuable in order to improve the understanding of a variety of physical phenomena that can be modeled numerically and simulated by computers. Amongst the possible applications, we could utilize immersive visualizations as a pedagogical tool for enhanced perception of complex topics, or as a powerful tool that helps engineers interpret the outcome of simulations. This research project approaches the use of immersive visualizations of electromagnetic fields, especially fields generated by wireless networks widely utilized in the everyday life, as is the case for networks of the type IEEE 802.11 (Wi-Fi). For such a purpose this work proposes new methods to three-dimensionally visualize time-varying electromagnetic fields, and distributions of interesting parameters related to wireless networks. To achieve these objectives, a better version of the finite-difference time-domain (FDTD) method is developed: the Coarse Grid Higher Order FDTD (CGHO-FDTD) method. Thus highly accurate, faster and more computationally efficient numerical solutions of Maxwells equations can be obtained. The numerical calculations are made even faster by the use of parallel computing on a cluster of computers. The characteristics of the time domain facilitate the creation of snapshots of the propagating electromagnetic fields, and in this manner it is possible to create three-dimensional figures and animations that can be used to explain some of the following common physical effects found in wireless networks: diffraction, reflection, and attenuation. To further enhance the perception of the physics, immersive visualizations are carried out in a virtual reality environment. Finally, the developed tool can also be used to create highly detailed distributions of important parameters that affect the performance in wireless networks. It is shown that simulations to predict the power distribution in an indoor wireless network of the type IEEE 802.11 (Wi-Fi), agree very well with measurements.
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Krahn, Alexander Philipp. „Hardware development to increase NMR sensitivity and spectral resolution by novel rf resonators and polarization transfer“. Lyon, Ecole normale supérieure, 2010. http://www.theses.fr/2010ENSL0561.
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Dans cette thèse, de nouvelles méthodes sont analysées afin d’augmenter la sensibilité, faible, du phénomène d’induction nucléaire grâce l’optimisation de l’instrument lui-même et par le couplage au moyen la Polarisation Dynamique Nucléaire (PDN). La première partie, est axée sur la bobine de mesure en contact avec l’échantillon et le circuit de sonde de RMN de l’état solide sous très hauts champs magnétiques. Le principe de réciprocité et les calculs de champ électromagnétique permettent une description physique des bobines ainsi qu’une optimisation de la géométrie des bobines de mesure. Dans ce contexte la problématique des champs électriques limite auxquels sont soumis les échantillons aux fréquences de Larmor élevées est prise en compte. Ce phénomène a toujours posé de sérieuses difficultés au moment de l’irradiation RF par des impulsions de découplage, cause d’une augmentation sensible de la température des échantillons dispersifs. Pour y remédier, des bobines innovantes, appelées LLC (Loop-gap Loaded Coil), issues de l’analyse numérique de la distribution du champ électromagnétique, sont introduites. Elles réduisent la composante électrique de l’onde électromagnétique dans le volume de l’échantillon. Cette étude est illustrée par la comparaison entre la simulation et l’étude expérimentale réalisée dans un champ statique de 16. 4 T. Dans la seconde partie, des résonateurs adaptés sont présentés pour appliquer la technique de la PDN, afin d’augmenter la polarisation des spins nucléaires par transfert de polarisation à travers le couplage des spins électroniques. Le dispositif expérimental mis en oeuvre relève du défi technique et exige la construction de structures doublement résonantes pour travailler aux fréquences de Larmor de l’électron et du noyau simultanément. Une procédure d’ajustement des modes est détaillée, celui-ci permet le calcul de la distribution du champ électromagnétique l’intérieur des cavités cylindriques, en tenant compte explicitement des propriétés diélectriques de l’échantillon. A partir d’un ensemble de modes dans les cavités résonantes, deux structures possibles sont retenues. Elles présentent des avantages complémentaires pour deux approches différentes expérimentales de la PDN. Des données expérimentales préliminaires sont présentées grâce à un prototype expérimental dans un champ statique 0. 35 T et 3. 5 TIn this thesis, methods are investigated to increase the inherently low detection sensitivity of the NMR experiment by an optimization of the detection hardware and by DNP experiments. In the first part, the emphasis is put on the sample coil and the rf circuitry of the NMR probehead, especially for conditions typical in high-field solid-state experiments. Based on a reciprocity principle and by electromagnetic field calculations, generalized coil parameters are derived and used to optimize the geometry of solenoid sample coils. In this context, the problem of fringe electric fields experienced by a sample at high Larmor frequencies is addressed. In the past, this has put severe limitations on the possibility to apply strong decoupling field amplitudes to temperature sensitive and dispersive samples. Resulting from the numerical field analysis of common NMR coils a novel sample coil geometry – the LLC resonator – is presented that significantly reduces the rf electric field in the sample volume. To characterize the novel structure, a comparative numerical and experimental study for a static field of 16. 4 T is demonstrated. In the second part, dedicated resonators are discussed to apply the method of DNP to increase the nuclear spin polarization by polarization transfer from coupled electron spins. The experimental setup of these experiments is challenging and requires the construction of double resonant structures operated at the electron and nuclear Larmor frequencies. An efficient mode-matching method is implemented that allows the calculation of the electromagnetic field distribution inside cylindrical cavities considering explicitly the dielectric properties of the sample. From the set of cavity modes, two potential resonator geometries are derived that are advantageous for two different experimental DNP approaches. Preliminary experimental data are shown that are measured with prototype resonators in a static field of 0. 35 T and 3. 5 T
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Gärskog, Gustav. „NUMERICAL CALCULATION METHOD FOR MAGNETIC FIELDS IN THE VICINITY OF CURRENT-CARRYING CONDUCTORS“. Thesis, Uppsala universitet, Elektricitetslära, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-353338.
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This thesis aims to develop a calculation method to determine themagnetic field magnitudes in the vicinity of power lines, i.e. bothburied cables and overhead lines. This is done through the numericaluse of Biot Savart's law where the conductors are approximated by aseries of straight segment elements that each contribute to the overallfield strength at the field point. The method is compared to two realcases and to the exact integral solution. Also, a review of some of theresearch material regarding electromagnetic fields from power lines andclaims of adverse health effects due to these fields is conducted.Results show that the numerical error is dependent on the segmentationdegree of the conductors and the mathematical model is inaccurate closeto the conductor. The calculations show slightly higher fieldmagnitudes than the previous survey done by WSP (Williams SalePartnership) far away from the source and slightly lower at the centerconductor. This may be due to the excluded induction in the shieldwires and differences in actual conductor coordinates.
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Sommer, Malte [Verfasser]. „The application of Krylov subspace methods for the calculation of forward solutions and model sensitivities of 3D time domain marine controlled source electromagnetic problems / Malte Sommer“. Kiel : Universitätsbibliothek Kiel, 2017. http://d-nb.info/1144269822/34.
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12
Gogornas, Alexandros. „Rigorous electromagnetic calculations in radiometry“. Thesis, Imperial College London, 2008. http://hdl.handle.net/10044/1/1374.
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Until recently, accurate estimates in radiometry using geometrical optics were justified because of the use of optical frequencies and large apertures. Nevertheless in modern radiometry, due to the increased interest in longer wavelengths and the improvement of experimental accuracy, geometrical optics cannot provide accurate enough estimates for experimental purposes. Initially the accuracy was improved by using the Fresnel approximation for the calculation of physical flux. Obviously this approach includes all the common approximations of scalar diffraction theories, namely scalar field, infinitely thin aperture and perfectly absorbing screen. Therefore, a more accurate model is introduced that accounts for the vector nature of light, finite thickness for the aperture and infinite conducting screen which is a good approximation because of the use of longer wavelengths. The application of this model, as well as abandoning the single wavelength approximation, results in deviations from scalar theory of 1% for a typical radiometric configuration.
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Šatava, Patrik. „Výpočet synchronního motoru s permanentními magnety o výkonu 50kW“. Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2021. http://www.nusl.cz/ntk/nusl-443091.
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This master’s thesis deals with a permanent magnet synchronous machine calculation. In the first part of the thesis, the synchronous machine in general is described. Knowledge of these machines is essential for the remaining parts of the thesis. In the next part, an analytical calculation process of a given permanent magnet synchronous machine is presented. The given machine had already been manufactured before the thesis assignment. The calculation is to be adapted to the given machine. This way the parameters of the calculated machine should match the reference machine. The accuracy of the calculation can then be evaluated. Furthermore, calculations of the machine using Ansys RMxprt and Ansys Maxwell 2D are presented. The calculations are then compared with data obtained by measurements performed on the given machine. In the last part of the thesis, a modification in the analytical calculation is made to reduce the inaccuracy of the calculation. The thesis is concluded by evaluating the results.
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Torokoff, Kristel. „Field Theories and Vortices with Nontrivial Geometry“. Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis : Universitetsbiblioteket [distributör], 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-6744.
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Haas, Christopher. „The projector basis method for electronic band structure calculations“. W&M ScholarWorks, 1996. https://scholarworks.wm.edu/etd/1539623886.
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Over the last several decades, two methods have emerged as the standard tools for the calculation of electronic band structures. These methods, the Car-Parinello plane wave method and the linear augmented plane wave method (LAPW), each have strengths and weaknesses in different regimes of physical problems. The Car-Parinello algorithm is ideal for calculations with soft pseudopotentials and large numbers of atoms. The LAPW method, on the other hand, easily handles all-electron and hard-core pseudopotential calculations with a small number of atoms. The projector basis method, presented here, is a hybrid mixed basis method which allows the calculation of moderately large ({dollar}\sim{dollar}200) numbers of atoms represented by hard pseudopotentials. This method will then be used to calculate two members of a relatively new mass of materials, called electrides, in which the anion has been replaced with a localized electron.
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Bidouche, Badr-El-Boudour. „Étude et réalisation d’une machine asynchrone basse vitesse à réducteur magnétique intégré“. Electronic Thesis or Diss., Université de Lorraine, 2019. http://www.theses.fr/2019LORR0228.
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Nous nous proposons dans ce travail d’étudier un entrainement par moteur à induction à rotor bobiné intégrant un réducteur de vitesse magnétique qui constitue la MaGIM « Magnetically Geared Induction Machines ». L’objectif est d’améliorer la fiabilité et les performances du système classique associant une machine asynchrone (MAS) à un réducteur mécanique (broyeur, concasseur…), la machine étant alimentée directement par le réseau. Nous dimensionnons un prototype MaGIM de 1 kW - 45 tr/min fonctionnant sur le réseau à 400 V/50 Hz en utilisant des outils de calculs analytiques et numériques permettant de prédire les performances électromagnétiques du dispositif. Nous présentons dans le premier chapitre un état de l’art des différents engrenages magnétiques étudiés depuis le 20ème siècle jusqu'à nos jours. Les différentes structures et topologies étudiées sont recensées. Compte tenu de sa complexité, nous avons modéliser la machine asynchrone et le réducteur de vitesse magnétique séparément, dans le chapitre II. Un modèle théorique de la machine prenant en compte les aspects électromagnétiques et thermiques a été développé pour obtenir un dimensionnement acceptable suivant un cahier des charges précis. Nous avons présenté les performances électromagnétiques du système obtenu ainsi que les calculs thermiques effectués par une méthode nodale. Le fonctionnement en régime transitoire de la machine par l’établissement d’un modèle analytique regroupant les équations mécaniques de la machine asynchrone et de l’engrenage magnétique a été présenté au chapitre III. Ce modèle nous a permis de déterminer les performances de la MaGIM lors d’un démarrage direct sur le réseau. Nous avons pu constater que la MaGIM peut démarrer sur le réseau sous pleine tension et que ce démarrage est fortement dépendant du moment d’inertie Jl. Cette étude nous a permis de mettre en évidence le phénomène de décrochage de la MaGIM et la particularité des engrenages magnétique à se protéger contre les surcharges. Dans le dernier chapitre, nous avons présenté la réalisation du prototype 1 kW, fonctionnant sur le réseau 400 V/ 50 Hz et délivrant 210 Nm en sortie à environ 50 tr/min. Le prototype a été réalisé dans l’atelier mécanique de VEDECOM - Mobilab. Des essais expérimentaux ont été effectués à l’issue de la réalisation dans le but de les comparer aux résultats théoriques et aussi de valider le concept de la MaGIMWe propose in this work to study a wound rotor induction motor integrating a magnetic gear which constitutes the MaGIM " Magnetically Geared Induction Machines ". The aim is to improve the reliability and the performances of the classical system associating an induction machine (MAS) with a mechanical reducer (mill, crusher...), the machine being fed directly by the network. Therefore, we designed a MaGIM prototype of 1 kW - 45 rpm operating on the grid at 400 V/50 Hz using analytical and numerical calculation tools to predict the electromagnetic performances of the device. In the first chapter, we present a state of the art of the different magnetic gears studied from the 20th century to the present day. The different structures and topologies studied are listed. Given its complexity, we have modelled the induction machine and the magnetic gear separately, in chapter II. A theoretical model of the machine taking into account the electromagnetic and thermal aspects has been developed in order to obtain an acceptable design according to precise specifications. We have presented the electromagnetic performance of the system obtained as well as the thermal calculations carried out using a nodal method. The transient operation of the machine by establishing an analytical model including the mechanical equations of the induction machine and the magnetic gear was presented in chapter III. This model allowed us to determine the performance of the MaGIM during a direct start on the network. We have seen that the MaGIM can start on the mains under full voltage and that this starting is strongly dependent on the moment of inertia Jl. This study allowed us to highlight the stall phenomenon of the MaGIM and the particularity of magnetic gears to protect themselves against overloads. In the last chapter, we presented the realization of the 1 kW prototype, operating on the 400 V/ 50 Hz network and delivering 210 Nm output at about 50 rpm. The prototype was produced in the mechanical workshop of VEDECOM - Mobilab. Experimental tests were carried out at the end of the realization in order to compare them with the theoretical results and also to validate the concept of the MaGIM
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Zhao, Yuanhong. „Fast Physical Optics Calculation for SAR Imaging of Complex Scatterers“. The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1338312941.
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Escarela, Perez Rafael. „Finite-element determination of two-axis transient parameters for the simulation of turbine-generators“. Thesis, Imperial College London, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.243518.
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19
Šimek, Petr. „Analýza dosahu signálu bezdrátových sítí“. Master's thesis, Vysoké učení technické v Brně. Fakulta informačních technologií, 2017. http://www.nusl.cz/ntk/nusl-363825.
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This master's thesis describes process of design and development of the system for calculating the coverage of wireless networks, it is implemented as a web portal and written in the Java programming language. The text of the thesis describes the work with the used platforms, a description of the ITU-R calculation method P.1812, which is used for calculation electric field strength and basic information about electromagnetic waves. The main function of the system is to calculate and display coverage of wireless networks and customer management information.
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Bílek, Vladimír. „Elektromagnetická analýza a modelování asynchronního stroje s plným rotorem“. Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2021. http://www.nusl.cz/ntk/nusl-442791.
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Tato diplomová práce se zabývá elektromagnetickou analýzou a modelováním asynchronního stroje s plným rotorem. Tato práce tedy zahrnuje literární rešerši na téma vysokootáčkových elektrických strojů s porovnáním s klasickými elektrickými stroji s převodovkou a popisem jejich výhod či nevýhod, rozdělení vysokootáčkových elektrických strojů s plnými rotory a srovnání jejich výhod či nevýhod, kde se tato práce nejvíce soustřeďuje na vysokootáčkové asynchronní stroje s plnými rotory a jejich použití v průmyslu. Dále se tato práce zabývá metodami výpočtu elektrických asynchronních strojů s plnými rotory. Proto jsou zde uvedeny a popsány metody výpočtu stroje mezi které patří analytické metody i metoda konečných prvků. Vzhledem k povaze elektrických strojů s plnými rotory je hlavně kladen důraz v této práci na výpočet stroje pomocí metody konečných prvků ve 2D prostoru s využitím korekčních činitelů konců plných rotorů, které jsou zde velmi detailně popsány a rozděleny. Na základě dostupné literatury je vypočítaný elektrický stroj s plným rotorem pomocí MKP analýzy. Elektromagnetický výpočet stroje je automatizován pomocí skriptu vytvořeného v Pythonu. Dalším hlavním cílem této práce je popis tzv. náhradních modelů, uvedení jejich výhod či nevýhod, použití v jiných průmyslových odvětvích a hlavně použití náhradních modelů na elektrický stroj s plným rotorem. S využitím náhradních modelů je dále optimalizovaný vybraný asynchronní stroj s plným rotorem a to pomocí programů SymSpace a Optimizer. Pro samotnou optimalizaci byly uvažovány 3 návrhy stroje, které byly na závěr mezi sebou porovnány a to hlavně z hlediska jejich elektromagnetického výkonu.
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Yang, Hung-Yu. „Novel Electromagnetic Responses in Topological Semimetals: Case Studies of Rare-Earth Monopnictides and RAlX Material Family“. Thesis, Boston College, 2021. http://hdl.handle.net/2345/bc-ir:109188.
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Thesis advisor: Fazel TaftiSince the idea of topology was realized in real materials, the hunt is on for new candidates of topological semimetals with novel electromagnetic responses. For example, topological states can be highly conductive due to a topological protection, which can be destroyed in a magnetic field and lead to an extremely high magnetoresistance. In Weyl semimetals, a transverse current that would usually require a magnetic field to emerge, can be generated by intrinsic Berry curvature without a magnetic field -- the celebrated anomalous Hall effect. In this dissertation, both phenomena mentioned above are studied in rare-earth monopnictides and RAlX material family (R=rare-earths, X=Ge/Si), respectively. The monopnictides are ideal for the study of extreme magnetoresistance because of their topological transitions and abundant magnetic phases. In LaAs, we untied the connection between topological states and the extreme magnetoresistance, the origin of which is clarified. In HoBi, we found an unusual onset of extreme magnetoresistance controlled by a magnetic phase dome. On the other hand, RAlX material family is a new class of Weyl semimetals breaking both inversion and time-reversal symmetries. In particular, in PrAlGeₓSi₁₋ₓ (x=0-1), we unveiled the first transition from intrinsic to extrinsic anomalous Hall effect in ferromagnetic Weyl semimetals, and the role of topology is discussed. In CeAlSi, we found that the Fermi level can be tuned as close as 1 meV away from the Weyl nodes; moreover, a novel anomalous Hall response appears only when the Fermi level is tuned to be near the Weyl nodes. Thus, we established a new transport response solely induced by Weyl nodes
Thesis (PhD) — Boston College, 2021
Submitted to: Boston College. Graduate School of Arts and Sciences
Discipline: Physics
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Dawood, Sami. „Etude du couplage d'une onde electromagnetique avec des cables souterrains (antennes et cables)“. Clermont-Ferrand 2, 1987. http://www.theses.fr/1987CLF2D197.
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Etude de la reponse d'un cable enterre infini a une impulsion electromagnetique. Determination de la repartition du courant induit par une methode modale. Etude du cas des cables de longueur finie par la theorie des lignes. Etude des impulsions exponentielle et en echelon
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Gouriou, Tristan. „Etude de l'impulsion électromagnétique et du plasma issus de la décharge de matériaux diélectriques soumis à une irradiation d'électrons“. Thesis, Toulouse 3, 2019. http://www.theses.fr/2019TOU30203.
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Dans l'espace, les matériaux diélectriques constitutifs des satellites sont susceptibles d'être exposé à des flux énergétiques de particules générés dans l'environnement terrestre à partir des rayonnements solaire et cosmique. Une des conséquences de cette exposition est l'apparition de décharges électrostatiques (ESD) qui naissent lorsque des électrons énergétiques pénètrent en profondeur dans des matériaux de faibles conductivités comme les polymères. Ces particules piégées sont responsables d'une élévation importante du champ électrique interne pouvant conduire à une rupture diélectrique du matériau suivi d'une évacuation des charges et de la formation d'un plasma qui s'étend dans le vide. L'impulsion électromagnétique intense qui en découle peut se coupler aux éléments d'interconnexion (pistes de circuit imprimé ou liaison filaire) et propager des signaux qui représentent une menace sérieuse pour l'ensemble du satellite. L'objectif de cette thèse est de mieux comprendre ces phénomènes de ruptures et de caractériser le plasma et l'impulsion électromagnétique générée. Les travaux de recherche comportent une partie expérimentale où les décharges sont reproduites au moyen d'un accélérateur linéaire d'électrons de 6 MeV irradiant différents polymères (polyéthylène, polytétrafluoroéthylène et polyméthacrylate de méthyle) dans une cavité sous vide. Les courants électriques induits et les champs électromagnétiques rayonnés sont quantifiés respectivement au moyen d'une pince de courant et de sondes de champs couvrant une bande spectrale allant jusqu'à 6 GHz. Les caractéristiques du plasma sont étudiées par absorption d'un signal radiofréquence injecté dans la cavité par un générateur de bruit blanc. Il a notamment été montré que la durée de vie du plasma s'étend jusqu'à la dizaine de microsecondes alors que les phénomènes électriques et électromagnétiques ne durent que quelques centaines de nanosecondes. Les résultats expérimentaux obtenus ont été confrontés aux résultats issus du code 3D de résolution des équations de Maxwell (code Sophie) développé au CEA. Les mesures du champ électromagnétique rayonné dans la cavité ont pu être restituées en injectant des profils spatio-temporels de densité de courant modélisant la rupture diélectrique du matériau. Le temps de montée de la décharge a pu être quantifié à une centaine de picosecondes. Les mesures d'absorption des signaux radiofréquences ont pu être restituées en modélisant l'expansion du plasma dans la cavité à l'aide de coquilles concentriques de conductivité variable. La vitesse d'expansion du plasma dans le vide a pu être établie à 105 m/s et la conductivité sur les premiers millimètres de l'expansion de l'ordre de la dizaine de S/m. Enfin, un modèle collisionnel-radiatif et un modèle simplifié de l'évolution spatio-temporel du plasma ont permis de faire le lien entre la densité de courant, la conductivité du plasma injectés dans le code Sophie et la densité et température du plasmaIn space, dielectric materials of satellites are likely to be exposed to energetic fluxes of particles generated in the terrestrial environment from solar and cosmic radiation. One of the consequences of this exposure is the appearance of an electrostatic discharges (ESD) risk that arise when energetic electrons penetrate deeply into low conductivity materials such as polymers. These trapped particles are responsible for a significant rise in the internal electric field that can lead to a dielectric breakdown of the material followed by a charges evacuation and plasma formation expanding into vacuum. The resulting intense electromagnetic pulse can couple with interconnection elements (conductive tracks of printed circuit board or wire connection) and propagate signals that pose a serious threat to the entire satellite. The objective of this thesis is a better understand of these dielectric breakdown phenomena and characterize the plasma and the electromagnetic pulse generated. The research includes an experimental part where discharges are reproduced by a 6 MeV linear electron accelerator irradiating different polymers (polyethylene, polytetrafluoroethylene and polymethylmethacrylate) in a vacuum cavity. The induced electric currents and electromagnetic fields are quantified respectively by current probe and magnetic field probes covering a spectral band up to 6 GHz. The characteristics of the plasma are studied by absorption of a radiofrequency signal injected into the cavity by a white noise generator. It has been shown that the lifetime of the plasma extends to about ten microseconds while the electrical and electromagnetic phenomena last only a few hundred nanoseconds. The experimental results obtained were compared with the results from the 3D code solving Maxwell equations (Sophie code) developed at CEA. Measurements of the electromagnetic field in the cavity could be restored by injecting spatial and temporal profiles of current density modeling the dielectric breakdown of the material. The rise time of the discharge could be quantified at a hundred picoseconds. Absorption measurements of radiofrequency signals could be restored by modeling the plasma expansion in the cavity using concentric shells of variable conductivity. The expansion velocity of the plasma in vacuum could be established at 105 m/s and the conductivity on the first expansion millimeters at about ten S/m. Finally, a collisional-radiative model and a simplified spatiotemporal plasma evolution model allow connection between current density, plasma conductivity injected into Sophie code and plasma density
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Benetka, Martin. „Analýza, návrh a optimalizace automobilového startéru“. Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2014. http://www.nusl.cz/ntk/nusl-220715.
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This thesis aims at automotive starters, their construction, characteristics and problems with starting at low temperatures. There are kinds of starters, function principle, construction, advantages and disadvantages in the first part of thesis. Issues with combustion engine starting and basic technical requirements are also mentioned here; characteristics and importance of starters and combustion engines are also described. Last chapters of this part are dedicated to finite element method and its implication. There are analytical calculations of starter in the second part of thesis. Results are compared with experimental obtained (measured) values and results from RMxprt. Finite element method results are compared, too. Magnetic induction improvement in stator is also suggested.
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Daněk, Michal. „Simulace toroidních cívek v Ansoft Maxwell 3D“. Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2009. http://www.nusl.cz/ntk/nusl-218197.
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The master thesis is focused on the simulation of the toroid coils in Ansoft Maxwell 3D software, which uses finite element method for electromagnetic field simulation. Firstly the process creation of the geometric model toroid coil with seventy-five threaded is presented. It is necessary to debug this model and prepare it for the mesh generation. Physical properties are assign to this model and it gives rise to the physical model. We will set boundaries, excitation current, core material, winding material and the parameters for the mesh generations. New material Kashke K4000 will be created in the materials library and subsequently we will define its BH curve on the basis of datasheet. Analysis is made in two modes. Direct currents (7,5A; 10A; 15A; 20A; 25A) and (non)linear materials are used in magnetostatic solution. Toroid coil is excited by current pulse in transient solution. In Ansoft Maxwell Circuit editor a source which generates current pulse will be created. This excitation will be assigned to the toroid coil as an extern source through a terminal. Core material is linear in the case of transient analysis, because Ansoft Maxwell 3D doesn´t allow to use nonlinear material in this solution. Settings are different in transient and in magnetostatic analysis. End time and time step are entered to solve this task in transient analysis. Time points are entered too. Flux density and electromagnetic field strength are calculated in these time points and later it will be possible to view the results. Calculated fields are shown as the pictures in this thesis. The procedure how to use a field calculator in the postprocessing is given as well. The achievements are summarized in the conclusion.
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WANG, RONG-HUI, und 王榮輝. „Calculation of electromagnetic transmission through a two dimensional duct“. Thesis, 1990. http://ndltd.ncl.edu.tw/handle/77061024217026347245.
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Li, Yu-Zhen, und 李玉楨. „Electromagnetic Force Calculation of Transverse Flux Linear Switched-Reluctance Machine by Finite Element Method“. Thesis, 1997. http://ndltd.ncl.edu.tw/handle/35928497375255040917.
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Ghorbani, A., Raed A. Abd-Alhameed, Neil J. McEwan und Dawei Zhou. „An Approach for Calculating the Limiting Bandwidth-Reflection Coefficient Product for Microstrip Patch Antennas“. 2006. http://hdl.handle.net/10454/3458.
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NoThe bandwidth of a microstrip patch antenna is expressed in terms of minimum achievable reflection coefficient using an equivalent circuit and the Bode-Fano theory. The bandwidth-reflection coefficient product is found to be proportional to antenna height and largely independent of feed probe position, for small bandwidths. The product can be computed directly from a numerical evaluation of the first-order Bode-Fano integral. Curves are presented showing how the product becomes limited by the feed probe inductance at very large bandwidths. It is concluded that this effect is unlikely to be a limit on the potential bandwidth of a practical patch antenna. If as a minimal correction the feed inductance is tuned out, the realized bandwidth with low order matching or optimal over-coupling shows the expected relationship to the theoretical limit.
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„Development of Software for Calculating Electromagnetic Fields Near High-Voltage Power Lines“. Master's thesis, 2015. http://hdl.handle.net/2286/R.I.35996.
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abstract: The electromagnetic fields near power lines that may produce adverse effects on humans are of increasing interest in a variety of situations, thus making it worthwhile to develop general-purpose software that estimates both the electric and magnetic fields accurately. This study deals with the simulations of the electric and magnetic fields near high-voltage power lines for the triangular, horizontal and vertical conductor arrangements under both balanced and unbalanced conditions.
For all three conductor arrangements, the shapes of the electric field distribution curves are different with the vertical arrangement best for minimizing right of way consideration, while the shapes of the magnetic field distributions curves are similar. Except for the horizontal arrangement, the maximum electric field magnitudes with shield conductors are larger than those without shield conductors. Among the three different arrangements, the maximum field value of the vertical arrangement is most vulnerable to the unbalanced conditions.
For both the electric and magnetic fields, increasing the heights of phase conductors gradually results in diminishing return in terms of the field reduction. In this work, both the maximum electric field magnitudes and the maximum magnetic field magnitudes produced by 500 kV power lines at 1 m height from the ground are all within the permissible exposure levels for the general public. At last, the dynamic trajectories of both fields with time are simulated and interpreted, with each field represented by a vector rotating in a plane describing an ellipse, where the vector values can be compared to high-speed vector measurements.Dissertation/Thesis
Masters Thesis Electrical Engineering 2015
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Maldovan, Martin. „Methods for Calculating the Optical Band Structure of Photonic Composites“. 2002. http://hdl.handle.net/1721.1/3981.
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Lately, there has been an increasing interest in studying the propagation of electromagnetic waves in periodic dielectric structures (photonic crystals). Like the electron propagation in semiconductors, these structures are represented by band diagrams in which gaps can be found where the electromagnetic propagation is forbidden. Much effort is dedicated to find structures that can prohibit the propagation of light in all directions. This effect could lead to light localization.Singapore-MIT Alliance (SMA)
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„Electric Field Calculations on Dry-Type Medium Voltage Current Transformers“. Master's thesis, 2012. http://hdl.handle.net/2286/R.I.15037.
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abstract: This research presents potential and electric field calculations on medium voltage (MV) epoxy insulated outdoor current transformers (CTs) using a numeri-cal calculation approach. Two designs of MV dry-type epoxy insulated CTs were modeled using 3D field simulation software COULOMB® 9.0. Potential and elec-tric fields were calculated based on boundary element method. Different condi-tions such as dry exterior surface, wet exterior surface and internal voids were considered. The research demonstrates that the presence of internal conductors in CTs results in a less severe surface electric field distribution when compared to outdoor insulators of the same voltage range and type. The high electric field near the exited end triple-point of the CT reduces. This remained true even under wet conditions establishing better outdoor performance of CTs than outdoor insulators which have no internal conductors. The effect of internal conductors on voids within the insulation structure was also established. As a down side, internal voids in CTs experience higher electric field stress than in conductor-less insulators. The work recognizes that internal conducting parts in dry type CTs improves their outdoor performance when compared to electrical equipment without internal conductors.Dissertation/Thesis
M.S. Electrical Engineering 2012
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Madsen, Jonathan R. „Monte Carlo Electromagnetic Cross Section Production Method for Low Energy Charged Particle Transport Through Single Molecules“. Thesis, 2013. http://hdl.handle.net/1969.1/151357.
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The present state of modeling radio-induced effects at the cellular level neglects to account for the microscopic inhomogeneity of the nucleus from the non-aqueous contents by approximating the entire cellular nucleus as a homogenous medium of water. Charged particle track-structure calculations utilizing this principle of superposition are thereby neglecting to account for approximately 30% of the molecular variation within the nucleus. To truly understand what happens when biological matter is irradiated, charged particle track-structure calculations need detailed knowledge of the secondary electron cascade, resulting from interactions with not only the primary biological component – water – but also the non-aqueous contents, down to very low energies.
This paper presents developments for a novel approach, which to our knowledge has never been done before, to reducing the homogenous water approximation. The purpose of our work is to develop of a completely self-consistent computational method for predicting molecule-specific ionization, excitation, and scattering cross sections in the very low energy regime that can be applied in a condensed history Monte Carlo track-structure code. The present methodology begins with the calculation of a solution to the many-body Schrödinger equation and proceeds to use Monte Carlo methods to calculate the perturbations in the internal electron field to determine the aforementioned processes. Results are computed for molecular water in the form of linear energy loss, secondary electron energies, and ionization-to-excitation ratios and compared against the low energy predictions of the GEANT4-DNA physics package of the Geant4 simulation toolkit.
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Yeh, Po-Fan, und 葉柏汎. „Calculations of electrostatic comb-drive rotational platforms, measurements of an MEMS gripper with two DOFs, and analyses of a trapping system using an array of electromagnetic micro-coils“. Thesis, 2010. http://ndltd.ncl.edu.tw/handle/02756524867388193801.
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碩士臺灣大學
光電工程學研究所
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Microelectromechanical system (MEMS) is popularly used in some many application, it has become a significant technique among our technological necessities including inkjet printer, airbag deployment in modern cars, game controller of Nintendo Wii, sensor embedded in iPhone, blood pressure sensor and pico-projector, etc. Micro-devices fabricated by MEMS technology containing: accelerometer, gyroscope, piezoelectric actuator, electro-thermal actuator, rotational platform, optical switcher, biosensor and chemosensor, etc. In this thesis, firstly an out-of-plane rotational platform using electrostatic combs will be introduced, especially the theoretical calculations with regard to applied voltage and rotational angles. The rotation angle is calculated to be ±1.81°, ±1.06° at 105V for the platforms with non-overlapping fingers and overlapping fingers, respectively. Also, the calculated result for the device with non-overlapping fingers agrees with experimental result, exhibiting ±2.3° at 105V (about 20% deviation). Secondly a micro-gripper with two degrees of freedom (in-plane and out-of-plane motions) based on an electro-thermal actuator will be studied. Design, fabrications, simulation and experiment of the MEMS gripper will be involved. Simulation for out-of-plane motion shows the arm of the MEMS gripper bends downward about 28 μm with added power of 12mW；and experimental results indicate that the in-plane tip displacement of the gripper is 138 μm at 2.7 V whereas the tip’s out-of-plane swing is 18 μm as the applied voltage varies from 0 to 90 V and vice versa. Finally, a trapping system using an array of electromagnetic micro-coils will be discussed, including design, calculation and experimental method. Magnetic particles are dripped upon microscopic glass which is placed on the array, and two electrical connections flow through the device can produce sixteen points of local magnetic fields. Besides, a small mass of nickel metal fabricated on the center of every micro-coil enhances the induced magnetic field which is calculated to be 42G at the surface of nickel metal.