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Evaluation of a switching device behaviour during short-circuit current
Fendrych, Martin ; Dostál, Lukáš (referee) ; Valenta, Jiří (advisor)
At work, I focused on the principle of electric arc extinction in low voltage devices. I particularly focused on the issue of magnetic switches. Next, I processed by the theory site issue of contact system in magnetic switches. In the practical part of my work, I was testing modular low voltage circuit breaker type of 2B and 10B. Testing was carried out in the laboratory of switchgear. I observed the movement of the contact and electric arc, which was burned between them and conductor wall. Observation was recorded by using a high-speed camera and an oscilloscope. Of acquired waveforms, I evaluated the dynamics of contacts, electric arc length and the value of the arc voltage for different moments.
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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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Static analysis of one joint of timber structure
Sedlák, Petr ; Gratza, Roman (referee) ; Kytýr, Jiří (advisor)
This diploma thesis deals with the numerical modeling of the nail joint of the timber roof structure and it is based on the already realized physical experiment. Totally twelve various solutions, where the isotropic and ortotropic characteristics of the spruce timber and steel components change, have been created. The final values of the joint shift obtained by using of the numerical modeling are compared with results of physical experiment. Program system ANSYS is used.
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Contacts between the culture of the Lepenski Vir and the first Neolithic populations at the turn of the 7th and 6th millennium
Ćosović, Mirza ; Popelka, Miroslav (advisor) ; Tichý, Radomír (referee)
(in English): This paper focuses mainly on the problem of the Mesolithic-Neolithic contact in the Iron Gates gorge at the turn of the 7th and 6th millenniums BC. A special emphasis is put on the eponymous site of Lepenski Vir. From a geographic point of view, this area represents a natural border between countries Serbia and Romania. There, in different layers and at different locations, were excavated and explored settlements documenting activities and social contact between the Mesolithic and Neolithic populations, as well as the transition from the Mesolithic way of life to the sedentary Neolithic one. The first part of the paper is devoted to an overview of scientific research, a development of views on the process of Neolitization and all the important aspects of culture. The second part deals with the examination of the first form of contact between Mesolithic and Neolithic populations based on the results of natural and archaeological research with theoretical application of the migration model, from the American anthropologist David W. Anthony.
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Contacts and Archaeology - the Example of Avar Khaganate and Western Slavs
Michaličová Nováková, Jana ; Profantová, Naděžda (advisor) ; Štefan, Ivo (referee)
The presented work focuses on the comparison of the basic characteristics of cultures inhabitating the area of today's Czech republic and the area of the historical Avar Khaganate in the time period betweeen half of the 6th century to the beginning of 9th century. The groundwork for this comparison is the study of 10 sites - 5 settlements and 5 cemeteries. Two cemeteries and two settlements are located in the centre of Czech republic, two and two others are located in the centre of khaganate, the remaining two are located in the border area between them. These sites show us parallels between both preseneted cultures. We can observe the similarities in funerary customs and in patterns of houses and settlements as well. Movable artifacts, some of which we may describe as luxurious ones, also undeniably reflect contacts between the Khaganate and areas of today's Czech republic. Key words Slavs, Avars, Contacts, Ethnicity, Archaeology, Early Middle Ages
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Contact erosion of switching devices
Píška, Jakub ; Šimek, David (referee) ; Valenta, Jiří (advisor)
This bachelor thesis deals with the erosion of contacts, as one of the negative phenomena affecting contacts of switchgears. In its first part, it briefly summarizes the other negative influences that must be considered when designing switching devices. In the following part, the physical mechanism of erosion and the primary criterion of assessment - weight loss are approached. The last and main part of the work deals with design of the contact system for comparing this loss for for frequently used materials and testing on a real switchgear. After the tests, the results were analyzed primarily from the perspective of ignition angles, the polarities of the current pulse and the current flowing through the arc. Taking into account the influence of the material composition, the size of the contacts and the presence of the arc-runner.
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Contact erosion of switchgear under real conditions
Holoubek, Josef ; Bušov, Bohuslav (referee) ; Valenta, Jiří (advisor)
This bachelor thesis is focused on the material loss - contacts erosion during switching process of the switchgears. First part is focused on the switchgears generally, their dividing and functions. Then there is closer look on the contacts of switchgears and what is necessary to be considered during their designing a operating. In this part there is also section devoted to the theory of the contacts erosion including the formulas for material loss calculation, which I found in existing literature. Practical part is focused on the contact system model and the measuring performed on this model. Measuring was also performed on the real switchgears for common use. There is also part devoted to this measuring. In the last part of thesis the analyze of the measured values is performed.
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Possibilities of companies advertisement on fairs
Fusková, Michaela ; Klasová, Jana (referee) ; Dvořák, Jiří (advisor)
The bachelor´s thesis is focused on promotion of TONDACH Česká republika, Ltd. company on the fairs. It includes informations of different kinds of advertising on the fairs, possibilities and exhibits how efektively turn fairs into a profits. Also which forms are effective and which aren’t. Above all this the bachelor is focused on proposition of the optimal structure of advert on the fairs.
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Evaluation of a switching device behaviour during short-circuit current
Fendrych, Martin ; Dostál, Lukáš (referee) ; Valenta, Jiří (advisor)
At work, I focused on the principle of electric arc extinction in low voltage devices. I particularly focused on the issue of magnetic switches. Next, I processed by the theory site issue of contact system in magnetic switches. In the practical part of my work, I was testing modular low voltage circuit breaker type of 2B and 10B. Testing was carried out in the laboratory of switchgear. I observed the movement of the contact and electric arc, which was burned between them and conductor wall. Observation was recorded by using a high-speed camera and an oscilloscope. Of acquired waveforms, I evaluated the dynamics of contacts, electric arc length and the value of the arc voltage for different moments.
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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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