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Electrodynamic forces acting on moving contact of electrical apparatus
Šic, Pavel ; Valenta, Jiří (referee) ; Bušov, Bohuslav (advisor)
This master’s thesis is focused on calculation, simulation and experimental verification of electrodynamic forces acting upon movable contact piece of MCCB and experimental current carrying path. A short description of low voltage circuit breakers is briefly discussed in first chapter. Second chapter is focused upon contact system analysis of particular MCCB with thermomagnetic trigger. A hardness of contact materials is briefly described. A detailed analytical calculations were used to determine electrodynamic forces in MCCB. A FEM simulation in ANSYS Maxwell was carried out for comparison with analytical results. An experimental apparatus was designed and built for verification of constriction repulsion force, so called Holm’s force. A series of measurements is subsequently performed on proposed apparatus and results are compared with results from previous chapters.
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Switching mechanism in the molded case circuit breaker
Mejzlík, Tomáš ; Valenta, Jiří (referee) ; Dostál, Lukáš (advisor)
This paper deals with mechanical switch in circuit breaker designed for low voltage. The goal of this thesis was to analyze switching mechanism both theoretically and practically. Theoretical analysis consist of study different types of switching mechanism and analytical calculations of acceleration speed and trajectory. Practical analysis has been made taking a video with high speed camera of real switching mechanism of a circuit breaker and software analysis of the data. The next part of a thesis is about 3D modeling, animating and simulating of a switchgear switching mechanism.
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Analysis of electrodynamic forces in electrcal apparatus
Dobrovolný, Jan ; Valenta, Jiří (referee) ; Šimek, David (advisor)
The master thesis deals with the phenomena called electro-dynamic force in the electrical apparatus. Nowadays, there are high requirements for electrical devices. The devices and especially their contacts are subject to high demands on reliability, reliability and mechanical durability. The electro-dynamic forces caused by the passage of electric current mechanically deform the current path. The design of the electrical apparatus must take these forces into account. Equations for electro-dynamic forces calculation are presented. In master thesis, individual parts of the current path are derived and described. Various configurations and designs of the current path are solved. The thesis also deals with the issue of forces in electrical contacts. Individual theoretical equations are then applied to a particular disconnector QAK, made by company IVEP, a.s. Parts of the disconnector were redrawn into 3D program SolidWorks. The model was analysed in program ANSYS Maxwell. The thesis compares the achieved results of analytical equations and numerical simulations.
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Arc optical diagnostics
Čermák, Jiří ; Valenta, Jiří (referee) ; Dohnal, Petr (advisor)
The aim of this bachelor thesis is to sort out the individual types of electric discharges, explain the ionization inside the plazma of the electric arc and the elucidation of the energetic balance inside the plazma. The electric arc is an undesirable and hardly predictable phenomenon occurring in switching devices during switching on and switching off the electric circuit. Some older methods of image processing obtained by a high-speed camera are also mentioned. Based on the images obtained from the camera, it is possible to make an equidensity or an equidensitogram that is used to monitor the arc in a quenching chamber. The second part includes the description of an experiment performed in a laboratory and the description of the high-speed camera used during this experiment. A modern method of the image processing using software Matlab is also described. An equidensitogram showing different levels of radioation was made in Matlab from the obtained images.
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Analysis of the stator and rotor pack termination effect on the synchronous machine by FEM
Michailidis, Petr ; Valenta, Jiří (referee) ; Skalka, Miroslav (advisor)
This thesis deals with simulation’s possibilities of the electromagnetic fields in electrical machines. A finite element method is the final element technique. The content of this thesis is a model and mesh creation and electromagnetic simulation of synchronous machine. The stator and rotor pack termination effect on the synchronous machine.is analyzed by finite element method in ANSYS program. The type of the stator termination pack is described by four segments. The magnetic field distribution is deformed due to the material properties of used segments. In the next part a methodics of mesh creation is shown. The mesh quality (in term of elements number and elements shape) is important due to the solution accuracy and speed.
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Simulation of circuit-breaker trip unit
Dostál, Lukáš ; Augusta, Zbyněk (referee) ; Valenta, Jiří (advisor)
Securing of electrical devices is important not only to protect against destruction under the effects of electric current, but also for protection of people or animals against electric shock. With increasing of living standards goes hand in hand increasing of the electricity consumption. Therefore In the grid of low voltage, there are increasing short-circuit currents. With improving technology is posed considerable demand on the performance, security and switching capacity of circuit breakers. This thesis is oriented on development of thermal and electromagnetic switch of circuit breaker on which is put a big demand in development of new types of circuit breakers. The thesis is interesting because of comprehensive use of circuits’ breakers since it can be used in AC and DC networks with frequency of 50 Hz and 400 Hz.
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Stress-strain Analysis of Dental Veneers
Valenta, Jiří ; Valášek, Jiří (referee) ; Marcián, Petr (advisor)
This thesis focuses on stress-strain analysis of the upper central incisor with applied veneer and its variations with proximal fillings and endodontic treatment. The basic materials and veneer types are introduced at the beginning. Next chapter describes the creation of geometric models of a healthy tooth, veneers and fillings. The veneer geometry model has been done in several variants, taking different thickness values, veneer ranges and used materials into account. A finite element mesh was applied to the models. The computation model was solved using the finite element method using the ANSYS 14.0 software in the Workbench graphics environment. The results of the analysis show that the composite material is more suitable for veneers placed partially in the dentin - either with proximal fillings or without them. The ceramic material is a better option for endodontic treatment. Veneers located in the enamel are not significantly affected by the choice of material and the ceramic material is more appropriate only when proximal fillings are applied.
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Selection of protective equipment for works done under voltage in low-voltage distribution grid
Kadlčík, Matěj ; Dadák, Petr (referee) ; Valenta, Jiří (advisor)
This bachelor thesis deals with the selection of suitable class of protective equipment for working under voltage in the low voltage distribution network. Working under voltage poses a serious safety risk for workers, especially in terms of the effects of an electric arc. Therefore, it is important to use appropriate protective equipment. In the theoretical part, this thesis deals with the risks of working under voltage in terms of the effects of an electric arc, describes available personal protective equipment, and explores available standards for protection against the effects of an electric arc. In the practical part, the thesis focuses on calculating the arc energy at various points in the low voltage distribution network and selecting the appropriate class of thermal protection for personal protective equipment.
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New requirements of photovoltaic system for family houses
Mička, Marek ; Valenta, Jiří (referee) ; Dostál, Lukáš (advisor)
The bachelor's thesis deals with the requirements for a photovoltaic system in a family house. Its aim is to summarize all important information when selecting a photovoltaic system. The first part of the semester project summarizes all used topologies of photovoltaic systems in family houses. The second part is devoted to the conditions for safe operation, which include normative requirements, design of lightning protection and connection to the distribution system. And the last third part deals with the process of enabling the parallel connection of the PV power plant to the distribution grid, development of project documentation and installation of PV technology.
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Morphology of the Abdominal Aortic Aneurysm
Eberlová, Lada ; Valenta, Jiří (advisor) ; Stingl, Josef (referee) ; Šebesta, Pavel (referee)
Dissertation Abstract Abdominalaortic aneurysm (AAA) is a serious disease. Its prevalence is in the developed countries about 3%. As an aneurysm is considered a dilatation of all layers of a vessel wall over 3 cm. Majority of AAA are small and asymptomatic, and although the risk of rupture increases with the size of aneurysm sack, even the small aneurysms rupture. The rupture mortaliry ranges about 70 %. Surgical treatment is indicated in the asymptomatic patients in diameter of AAA over 5 cm. The average speed of growth of AAA is 0.3 cm per year, e.g. in the early diagnosed patients there is a several years interval for a pharmacolocical influencing of the progression of this disease. Knowledge of pathogenesis is essential for any targeted pharmacological treatment. Our prospective, non-randomised studies are based on the application of the stereological methods for the histopathological assessment of the AAA samples. The acquired data enable the statistical analysis, including the null hypothesis testing. In our study analyzing the histopathology of AAA aortae of 65 patients (65 walls and 55 thrombi) and 6 normal abdominal aortae from the organ donors we assessed the following parameters: the area fractions of collagen and elastin, and the length density of elastin in intima and media, the area...
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