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Theoretical modes of electric arc
Vondrák, Michal ; Šenk, Josef (referee) ; Lázničková, Ilona (advisor)
This thesis deals with theoretical models of the electric arc. Plasma arc and plasma torch are explained. Basic approaches of electric arc modeling are described. The indirect method for the determination of the mean temperature and velocity at the exit of plazma jet plasmatron are discussed. Finally the simplified model with axially-cooled electric arc is described.
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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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Usage of high-speed camera in the area of switching arc
Samohejl, Matěj ; Bušov, Bohuslav (referee) ; Valenta, Jiří (advisor)
This bachelor´s thesis is focused on optimizing recording of electrical switching arc in magnetic switches by high-speed camera. Measurements were performed on the circuit breaker 10B without removed side case, which was subsequently cowled by neutral density filter. The voltage and current of the circuit breaker contacts were acquired by measuring system of the Laboratory of switching arc diagnostics. The energy source was motor-generator with a nominal power 16 MVA and test bench consisting of a capacitors and inductors, which have been tuned to the resonance frequency of 50 Hz. Evaluation of the measurements was taken with regard to the brightness distribution levels of the record. Results showed that the mean brightness value varies on the square of the current passing through. For proper localization of the arc, it is necessary to appropriately set the camera exposure. The main problem usually is to darken the scene enough. It was found that it is necessary to take into account that brightness level change depends nonlinear on the exposure offset. The thesis gives a proposal to determine the exposure shift of the record. The possibility of usage high-speed camera to determine the temperature distribution in the arc using the brightness equiintensities was also designed. There are mentioned suggestions how to improve recording of the arc in circuit breakers, especially in the arrangement of the optical parts.
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Electric arc in the switchgear
Kutal, Ondřej ; Dohnal, Petr (referee) ; Bušov, Bohuslav (advisor)
This thesis focuses on description of creation, properties and behavior of an electric arc in the switchgear. In addition, it focuses on description how an electric arc can be created and how it effects contacts in electrical switchgear. Electric arcs is divided into arc with DC or AC. Quenching of the electric arc supplied by DC is more difficult than in case of AC since the DC does not pass through zero value. For the design of quenching chamber it is important to know the characteristics of the electric arc under both conditions. The behavior of static V-A characteristic of the electric arc supplied by DC was determined with experimental measurements using the equation by Ayrton. Subsequently, measurement of the dynamic characteristics of the electric arc with AC were determined. And the limits values for the emergence of electric arc were measured of. Last, the results wereevaluated and expansion of measurement task was proposed. The numerous influences on the arc were described. In conclusion the thesis extends diagnostic of the arc under the laboratory conditions.
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The arc extinction in electrical apparatuses
Karásek, Ladislav ; Valenta, Jiří (referee) ; Bušov, Bohuslav (advisor)
My bachelor’s thesis is focused on theoretical analysis of the issues of switching arc in electrical devices, introducing successful quenching principles in present devices and the practical part of thesis is focused on innovation of lab exercises „Static V-A characteristics of DC (direct-current) arc and dynamical V-A characteristic of AC (alternating current) arc“, which is part of the course Electrical Devices. Part of the bachelor´s thesis is practical measuring of DC and AC arc, construction of static and dynamic characteristics and its subsequent reviews. The last part of my bachelor´s thesis is focused on innovation of this lab exercis
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Enhancement of optical diagnostics of the switching arc
Samohejl, Matěj ; Kloc, Petr (referee) ; Valenta, Jiří (advisor)
This master´s thesis si focused on determinig methodology of optical diagnostics of the switching arc using the high-speed camera Photron SA-X2. The thesis contains basic rules for proper setup of the measurement system and the rules to adjust the camera exposure. The experiments were performed on the prototype of a parametric switching chambre, while the majority of source materials was derived from the requirements of another study which was aimed on the movement of the electode spots. The process of the first adjustment of the camera, a record edit options for the presentation purposes and the process of the 3D model design of the switching arc in SketchUp software was stated. Paper contains a comparsion of the spectral filter effect and neutral density filter effect on the final record as well. The part of the work outputs are the 3D model of the switching arc and the supporting record editing software. The paper results show a degree of the inaccuracies in a optical diagnostics made from only one direction caused by the lack of the information about third dimension.
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Influence of welding direction on depth of penetration for MAG method
Šmak, Radim ; Mrňa, Libor (referee) ; Kubíček, Jaroslav (advisor)
This bachelor thesis deals about Influence of welding direction on depth of penetration in S 235 JR steel for MAG welding. First theoretical part of the thesis was devoted to a description and technology of the chosen method. In the second practical patr of the thesis was designed optimal welding parameters and conditions of welding. Based on them was performed an experiment. From the experiment was detected the depth penetration, heat affected zone and structure of the metal.
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Optimalization of electric arc furnace operation
Mikulinec, René ; Raček, Jiří (referee) ; Lázničková, Ilona (advisor)
The bachelor thesis deals with issues of electric arc furnaces and therefore the introductory part focuses on electric arc and its distribution according to the type of power. There is also stated the distribution of arc furnaces and heavy-current arc furnace circuit. Another part of the bachelor thesis is devoted to interferences, which operate the power network and the possibilities of reducing these interferences. The aim of this bachelor thesis is to optimize the operation of electric arc furnaces and that is the reason for the stating of the calculation of optimal parameters arc furnace with a circular diagram.
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Usage of CAD Systems in Area of Electrical apparatuses
Bojanovský, Lukáš ; Kuchyňková, Hana (referee) ; Valenta, Jiří (advisor)
This thesis presents current possibilities of parametric modelling. In the first section the new features of Autodesk Inventor Series 10 and process of designing model of arc chute cut of circuit-braker BD250 are described. A next section of the thesis describes funcionality of double contact element during switching off, creation and disappearance of electric arc. The principle of electric arc exctincion using magnetic exhaustion into arc chute with the participation of dynamic forces. The data format IGES was used for animation creation and also there is a short description of the history and origin of the format. The position animation in Autodesk Iventor 10 was used for designing animation.
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Experimental verification of properties of circuit breaker quenching chamber
Kadrnka, Petr ; Vávra, Zdeněk (referee) ; Valenta, Jiří (advisor)
The circuit breakers are able to switch on and off automatically either the short circuit currents up to the limits of their breaking capacity. While the disconnection of the contacts in the switching devices are generated by the arc then it is needed to put it out quickly. A manner of the arcing in the electrical switching devices is influenced by several different factors. It must be taken into account the dynamics of a plasma, a current flowing in the electrodes, a flowing stream in a plasma and a magnetic field generated by a flowing current. This paper is devoted to describe the manner of the arcing in the arc chamber. The experiments carried out in an experimental way attempt to explain, specify and thoroughly comprehend the movements and the characteristics of the arc in a metal arc and in a metal enclosure circuit breaker.
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