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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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Simulation of temperature-rise in MV switchgear assemblies
Kapalla, Alexej ; Bušov, Bohuslav (referee) ; Valenta, Jiří (advisor)
This thesis focuses on the issue of heating of medium-voltage switchgears. The paper contains descriptions of the individual devices which the switchgear consists of. Furthermore, the paper examine the theoretical relations which describe the heating of the conductor. It also present the normative regulations regarding the heading of MV switchgears as well as specific impacts which influence the final temperature-rise. This is followed by chapters that describe the refining of a 3D model of specific switchgear for purposes of simulating temperature-rise, further followed by chapters that look at the actual simulation environment. The thesis further focuses on the actual simulation of MV switchgear temperature-rise and it will compare the results of the simulation with measurements taken under real conditions. The thesis also includes results of simulated temperature-rise while taking into consideration the forced cooling of the switchgear. In the last part, it focuses on the creation of an excel file, which enables the prediction of final results for the temperature-rise of disconnector based on its contact resistance.
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Design of MV contactor for railway application
Pala, Lukáš ; Šimek, David (referee) ; Valenta, Jiří (advisor)
In the introduction a traction circuit is analyzed with different types of electric devices. The thesis describes power railway electric circuits, their loads and types of used contactors. Railway standards chapter summarizes requirements of standards for railway contactors. Follows literature focusing on power current switching and power switching devices design. Based on previous, a design procedure is developed for railway MV contactor in accordance with end-user and standards requirements. Thesis closes with pre-designing a railway contactor by calculating electrodynamic forces, heatflow and mechanical components.
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Measurement of mechanical and electrical quantities of bimetals
Kocian, Štěpán ; Bušov, Bohuslav (referee) ; Valenta, Jiří (advisor)
This bachelor thesis focuses on bimetals. In the theoretical part is described the principle of operation of bimetals, then important parameters of bimetal, including mathematical equations. Furthermore, methods of heating bimetals are mentioned and mathematically described. The last part in theory concentrates on the standards related to the use of bimetals as circuit breakers and the corresponding agreed breaking currents. The practical part deals with measurements on bimetal. This is measurement of free deflection and the force generated by the bimetal depending on the temperature change. From the measured data, the characteristics and the dependences of the properties for bimetal were processed. The last chapter was devoted to the creation of laboratory work.
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Electrodynamic forces in low voltage switchgear assembly
Moravec, Štěpán ; Bušov, Bohuslav (referee) ; Valenta, Jiří (advisor)
This bachelor thesis is focusd on issues of forces which are consecquences of an electrical current in an electric low-voltage switchboards. These forces are an effect of the magnetic fields arised from the electric current flowing in a circuit. We have to design electric switchboards which are in the process of use with emhasis on their safety, because the arisen forces are very high especially in a short-circuit. Each of new construction of an electric switchboard has to pass the type test in a testing laboratory for garanting their safety in operation. This thesis also examines the simulation on 3D model of an electric switch board by OEZ.
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Assessment of the design of a small photovoltaic power plant for a family house and elaboration of its revision process
Vozárik, Michal ; Valenta, Jiří (referee) ; Veselka, František (advisor)
This bachelor thesis includes the issue of photovoltaics with a specific photovoltaic power plant, supplemented by basic measurements during inspection activities. In the first part, the author deals theoretically with solar radiation and the photovoltaic field. In the second part of the work, the author deals with the issue of revision activities. Within the work, a specific design of a small photovoltaic power plant on the roof of a family house is assessed. Various sizing software were used to analyze and assess the object. Part of the work is also the procedure of verifying the parameters of the PV plant and the inspection report of the revised electrical equipment.
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