<p>Electromagnetic transients impinging on electromagnetic power devices - such as electric machines, transformers and reactors - can stress the design severely. Thus the magnitudes of the transients are often decisive for the design of the devices. Further, the operation of a device can be transient in itself. This is the case for the explosive magnetic flux compression generator (EMG) and a ferromagnetic actuator. </p><p>Models are presented that are mainly intended for transients in the millisecond range and faster. Hence, eddy currents and the related skin and proximity effect become significant in windings, magnetic cores and in the armatures of the devices. These effects are important for, e.g., the damping of the transients. Further, the displacement current in the insulation of the winding is significant. It changes the response of the windings dramatically, as it manifests the finite velocity of propagation of the electromagnetic fields. Under such circumstances, reflections and excited resonances can make the transient voltage and current distribution highly irregular. </p><p>Induced voltages are modelled with self and mutual inductances or reluctances combined with winding templates. The displacement currents are modelled with capacitances or coefficients of potential. Cauer circuits and their dual form are used to model eddy currents in laminated cores and in conductors. The Cauer circuit enables one to consider hysteresis and the non-linear response of a magnetic core. It is also used to model the eddy currents in the moving armature of an EMG. </p><p>A set-up is presented that can be used to study the transient voltage and the current distribution along a coil. </p><p>The transient response of coaxially insulated windings is analysed and modelled in detail. A lumped circuit model is developed for a coil, Dryformer^TM - the new high-voltage transformer - and Powerformer^TM, the new high-voltage generator. An alternative model, a combined lumped circuit and FEM model, is presented for a coaxially insulated winding in two slot cores.</p>

Electromagnetic transients impinging on electromagnetic power devices - such as electric machines, transformers and reactors - can stress the design severely. Thus the magnitudes of the transients are often decisive for the design of the devices. Further, the operation of a device can be transient in itself. This is the case for the explosive magnetic flux compression generator (EMG) and a ferromagnetic actuator. Models are presented that are mainly intended for transients in the millisecond range and faster. Hence, eddy currents and the related skin and proximity effect become significant in windings, magnetic cores and in the armatures of the devices. These effects are important for, e.g., the damping of the transients. Further, the displacement current in the insulation of the winding is significant. It changes the response of the windings dramatically, as it manifests the finite velocity of propagation of the electromagnetic fields. Under such circumstances, reflections and excited resonances can make the transient voltage and current distribution highly irregular. Induced voltages are modelled with self and mutual inductances or reluctances combined with winding templates. The displacement currents are modelled with capacitances or coefficients of potential. Cauer circuits and their dual form are used to model eddy currents in laminated cores and in conductors. The Cauer circuit enables one to consider hysteresis and the non-linear response of a magnetic core. It is also used to model the eddy currents in the moving armature of an EMG. A set-up is presented that can be used to study the transient voltage and the current distribution along a coil. The transient response of coaxially insulated windings is analysed and modelled in detail. A lumped circuit model is developed for a coil, DryformerTM - the new high-voltage transformer - and PowerformerTM, the new high-voltage generator. An alternative model, a combined lumped circuit and FEM model, is presented for a coaxially insulated winding in two slot cores.

Amorphous and polycrystalline microwires cast from ferromagnetic Fe-based or Co-based alloys in glass envelope demonstrate unique magneto-anisotropic and high frequency impedance properties that make them very attractive for sensor applications. Magnetic anisotropies of different types result from the inverse magnetostriction effect (positive or negative) at the interface between the glass shell and the metal core, in the presence of the residual stresses induced during the Taylor-Ulitovski casting method. Therefore, the glass shell is not just isolation, but also is one of most important factors that defines the physical properties of microwires. In particular, magnetic anisotropy allows high frequency impedance to be tuned by external stimuli such as magnetic field, tensile stress, or temperature. In the project, these effects are explored for the creation of low density microwire inclusions that might introduce tuneable microwave properties to polymer composite materials. The project aims to study high frequency impedance effects in ferromagnetic wires in the presence of tensile stress, temperature, and magnetic field. The integration of microwave equipment with mechanical and thermal measurement facilities is a very challenging task. In the project, we develop new experimental techniques allowing comprehensive study of composite materials with electromagnetic functionalities. The wire surface impedance recovered from such measurements can then be used to model the microwave response from wire-filled composites in free space. The obtained results significantly expand the horizon of potential applications of ferromagnetic wires for structural health monitoring.

Orientadores: José Pissolato Filho, Eduardo Coelho Marques da Costa / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação / Made available in DSpace on 2018-08-25T04:23:41Z (GMT). No. of bitstreams: 1 Monteiro_JoseHumbertoAraujo_D.pdf: 2599049 bytes, checksum: 247f68cef0523b44c3d1e9c69dc48119 (MD5) Previous issue date: 2014 / Resumo: Este trabalho apresenta o desenvolvimento de um modelo de linha de transmissão trifásica utilizando uma nova implementação do efeito pelicular, além do estudo da resposta transitória obtida a partir do referido modelo quando surtos de manobra são simulados. A metodologia tradicionalmente utilizada para o cálculo da impedância interna de cabos sólidos cilíndricos faz uso das funções de Bessel, o que a torna complexa. A metodologia descrita por Gatous é tão precisa quanto a metodologia que utiliza as funções de Bessel e possui a vantagem de ser mais simples, visto que a solução final é um somatório cuja precisão depende da frequência estudada. O modelo desenvolvido neste trabalho emprega a metodologia de Gatous em uma linha de transmissão trifásica, cujos modos de propagação independentes são obtidos a partir da aplicação da matriz de Clarke. Para validar a metodologia de Gatous, foram calculadas a resistência e a indutância interna de cabos com raios variados em uma ampla faixa de frequências. Os resultados foram comparados aos obtidos a partir da metodologia tradicional. A metodologia de Gatous reproduziu com precisão a variação da impedância interna com a frequência. Para avaliar o funcionamento do modelo de linha de transmissão trifásico no domínio do tempo, um caso base foi estabelecido. Uma linha de transmissão trifásica de 69kV, circuito simples, foi submetida a chaveamentos de carga em duas situações distintas: chaveamento sendo executado no ponto de cruzamento com o zero da tensão e; chaveamento no ponto de 90° da tensão. Os transitórios de tensão e corrente foram obtidos a partir do modelo elaborado e comparados com os resultantes do software de análise de transitórios ATP. Os resultados alcançados reproduzem com fidelidade o comportamento transiente descrito pelo software supracitado / Abstract: This paper presents the development of a three-phase transmission line model using a new skin effect calculation and its transient response when some switching surges are applied to it. The methodology commonly used to calculate the internal impedance of solid conductors with cylindrical cross sectional area employs Bessel functions, which makes it a hard task to accomplish. Gatous, in his doctoral work, presented a new method to calculate skin effect impedance as accurate as Bessel¿s methodology with advantage of simplicity, whereas that final solution is an algebraic sum whose precision depends of frequency studied. The transmission line model developed in this work utilizes Gatous¿s method for skin effect impedance calculation in a three-phase transmission line, whose independent modes of propagation are obtained from the application of Clarke's matrix. In order to validate the mentioned methodology, internal resistances and inductances of cables with different size radii were calculated for a wide range of frequencies. The results were compared with those obtained through the traditional method, reproducing correctly the variation of the internal impedance with frequency. A base case was established to evaluate the operation of the three-phase transmission line in the time-domain model. A 69kV three-phase transmission line, single circuit, was subjected to switching load in two distinct situations: switching at zero crossing voltage and switching at voltage peak. Voltage and current transients were obtained from the developed model and compared with those derived from transient analysis software ATP. The results faithfully reproduced the transient behavior described by the above software / Doutorado / Energia Eletrica / Doutor em Engenharia Elétrica

The current study presents an induction heating system design for fiber optics pipes joints. Remote heating methods are probably inconvenient due to non-uniform heat distribution resulting in unreliable joints. The induction heating generates uniform heat distribution which can be achieved by proper designing of inductive heating coil, and power system inverter that drives the induction system. Two different shaped open jaw type heating coils were designed i.e open claw type coil (OCTC) and curved spiral rectangular coil (CSRC). The coils were designed in COMSOL simulation software to check the coil and workpiece behaviours. These coil designs were then wounded by hand and resistance and inductance of each coil were measured. The OCTC is a short loop coil, having small inductance while the CSRC has a long loop so its inductance is high. CSRC design was selected in the current application. The CSRC inductance was calculated through modified Wheeler formula and current sheet approximation. To design the power inverter, firstly the power density of heating material i.e workpiece was calculated. Then the thermal losses of the coil were calculated, these losses were due to skin effect and proximity effect; and switch losses due to drain to source resistance(RDS) of Mosfets were estimated. The Mazzilli inverter was proposed for power system inverter design which works as a parallel resonant circuit. It was designed in Mandi simulation software and then implemented on hardware. Theoretical results were compared with the practical measurements through Matlab software. Coil efficiency, power inverter efficiency and overall system efficiency were also calculated. This induction heating method for fiber optics joints is repeatable, consistent, generates uniform heat and is more convenient for site-specific heat generated on workpiece. It is portable, user friendly and environmental friendly as well.

This term paper is focused on theory and calculation of an induction motor with solid rotor. It is divided into six chapters, the first one being an introduction and the last being a conclusion. Second chapter is dedicated to magnetism. There is briefly description of a skin depth of a conductor and calculation method for impedance of a conductive solid. Third chapter is focused on theory of an induction machines, their construction, equivalent circuit and some of their properties. Fourth chapter is dedicated to calculation of an induction motor with solid rotor and its parameters. Fifth chapter is comparing results of calculation done in fourth chapter for an already existing motor with measured values.

This master thesis deals with the suppression of the skin and proximity effects in high-speed machines. The first part summarizes the general knowledge of high-speed machines. The second part is devoted to the principle and possible suppression of consequences caused by skin and proximity effects. The third part shows the simulation results of models of a synchronous machine with permanent magnets. The results of these simulations reveal the consequences of skin and proximity effects. In addition, design measures are proposed to limit these and other undesirable phenomena to achieve the highest possible efficiency.

The aim of the project was to prepare the given model of the current path in the environment of the SolidWorks programme, in order to simulate the flow path in the environment of the Ansys programme, where there was calculated the distribution of current density,voltage drops and heat loss on the the specified current track according to specified conditions. The obtained results are analyzed at the conclusion of this work.

This master’s thesis deals with the calculation of electrodynamic forces breaker BD250NE305. Main tasks in this semester project is to study the theoretical analysis of individual parts specified breakers. Processing theoretical analysis of these forces. Creating a 3D model current path and sheets quenching chamber single phase circuit breaker in Autodesk Inventor Professional 2012. Another challenge is the subsequent export the model into the simulation program ANSYS Maxwell. After simulation, the specified conditions must be processed and the results of the present work is to evaluate.

An electrical bushing is one of the most important elements in a power transformer. Steep front surges such as transient impulse voltage from lightning strikes is an inevitable electromagnetic transient mostly happening in power transmission and distribution system. The bushing might lead to be degraded due to such kind of surge. This project deals with overvoltage stress distribution on the transformer bushing under the effect of electromagnetic transient response such as lightning impulse.  To understand the behavior of transient response on the bushing, a proper model of power transformer bushing is built-in Comsol multiphysics to authenticate the stress distribution. The electromagnetic wave of impulse propagates onto the overhead line that connects with the transformer. Some understanding of the transient behavior of a conductor bushing has been achieved through studying the influence of inductance property and the skin effect characteristics of a multi-layer coaxial cable on the wave propagation, which has been structured in this project to simplify the model. On the other hand, the skin effect analysis on the conductor of the bushing has been taken also into account in this project using real conductor simulation in the Comsol model. Thus, it will be interesting to compare the real conductor model with the perfect conductor of the bushing through analyzing the current density effect on it.  In this project, multi-layer of coaxial cable and transformer bushing are simulated. The simulation is carried out for time domain and frequency domain in Comsol based on the model characteristics. / En elektrisk genomföring är ett av de viktigaste elementen i en transformator. Spänningsvågor med branta fronter som impulsspänningar från blixtnedslag är ett oundvikligt elektromagnetiskt övergående fenomen som oftast sker i kraftöverförings- och distributionssystem. Genomföringen kan leda till att degraderas på grund av en sådan våg. Detta projekt handlar om fördelning av överspännings på transformatorgenomföringen under påverkan av elektromagnetisk transient respons, såsom blixtimpuls.  För att förstå beteendet hos övergående respons på genomföringen är en korrekt modell av transformatorgenomföring inbyggd Comsol-flerfysik för att autentisera spänningsfördelningen. Den elektromagnetiska impulsvågen fortplantas från luftledningen som ansluter till transformatorn. Viss förståelse för det övergående beteendet hos en ledargenomföring har uppnåtts genom att studera påverkan av induktansegenskaper och hudeffektegenskaperna hos en flerskikts koaxialkabel på vågutbredningen, vilket har strukturerats i detta projekt för att förenkla modellen. Å andra sidan har hudeffektanalysen på genomföringens ledare beaktats i detta projekt med användning av verklig ledarsimulering i Comsol-modellen. Således blir det intressant att jämföra den riktiga ledarmodellen med den perfekta ledaren för genomföringen genom att analysera strömtäthetseffekten på den.  I detta projekt simuleras flerskikt av koaxialkabel och transformatorgenomföring. Simuleringen utförs för tidsdomän och frekvensdomän i Comsol baserat på modellegenskaperna.