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Idea design of experimental model for LV electric arc properties investigation
Fazekas, Tibor ; Valenta, Jiří (referee) ; Vávra, Zdeněk (advisor)
The aim of the work was a planing of an experimental model for the observation of the low voltage electric arc. The opening part observes the basics of the electric network switching and the electric arc in theory. The next point is definition about the behaviour of the electric arc in the low voltage switching devices, focusing on the movement of the arc along electrodes and in the extinguish chamber. The design of the experimental model, created in Autodesk Inventor 2008, is described in the last part of the work.
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Welding of steel C45
Hála, Kamil ; Sigmund, Marian (referee) ; Kubíček, Jaroslav (advisor)
The aim of this bachelor‘s thesis is to propose a suitable welding parameters for a small part of steel C45. This steel contains a high percentage of carbon and therefore is difficult to weld. Gas shielded arc welding techniques were considered to be used, and from such techniques, the TIG method seems to be the most advantageous one. For this technique were suggested three groups of parameters and the most suitable one was chosen to be used for the production. The option chosen is of a welding power I=40 A and with preheating 200 °C. The component is made in the single-part production in SAAB Czech s.r.o.
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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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Switching arc plasma diagnostics by usage of two high-speed cameras
Buchta, Martin ; Dostál, Lukáš (referee) ; Valenta, Jiří (advisor)
This bachelor thesis deals with an electrical arc formation and its properties. The thesis also describes some of the electrical devices and principles, which are used for arc extinction. It is mainly focused on design, construction and testing of model of the LV quenching system, which allows high speed cameras to record arc movement. Recorded images are then used to create three-dimensional reconstruction of the electric arc with help of created program 3DMaker. The final reconstruction is the output of this work.
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Spectroscopic analysis of an electric arc
Hartman, Tadeáš ; Kloc, Petr (referee) ; Šimek, David (advisor)
The bachelor thesis deals with spectroscopic diagnostics of electric arcs. The first part explains the creation and properties of electric discharges, especially electric arcs. Methods for composition and temperature analysis of electric arcs are also given there. The next part deals with practical use of these methods for identification of elements contained in electrodes between which an arc discharge was happening, measurement of the arc temperature and also measurement of the temperature of the electrodes. In the last part, these methods are also used for the analysis of time progression of composition and temperature of an electric arc created on a contactor's contacts with the resistive load.
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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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The effectiveness of welding on furnace structures.
Rousová, Michaela ; Mrňa, Libor (referee) ; Kubíček, Jaroslav (advisor)
This diploma thesis is resolving all the possibilities of enhancing the efficiency of furnace structures welding. Small batch production does not offer many possibilities for implementing mechanization or automation. On the other hand, when using a big batch production, efficiency can be enhanced by means of a robotic workstation. When the production batch is big enough, we will see a costs save after a short time, mainly in labor costs. This means the return of investments will be in short time period. In the LAC company there are three types of products made. At laboratory furnaces the efficiency can be enhance by using fixtures. At other standard and atypical furnaces is very difficult to design fixtures or positioners because of their different sizes. Big complication can be also a company location on second floor. The most suitable product regarding to welding efficiency enhancement is big batch production of heaters. For this type the welding time can be shortened by means of a robotic workstation.
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Design of a welded go-cart frame
Kůřil, Michal ; Izák, Josef (referee) ; Kubíček, Jaroslav (advisor)
The work is focused on the design of a welded go-kart frame. The frame is welded from 32 mm tubes and 2 mm wall thickness. The material 25CrMo4 was chosen as it is widely used for frame structures in motorsport. The CNC CO2 laser was chosen to cut the tubes. Universal welding jigs were chosen due to the single piece production. Furthermore, metallographic tests of three samples were performed. Two were TIG welded, and one was MAG welded. There was chosen an austenitic filling material, which has good tenacity, and it is assumed to provide long lifespan while being mechanically loaded. Also, the Vickers hardness test was done.
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Testing of arc protection AFDD during normal and fault conditions
Křepela, František ; Dostál, Lukáš (referee) ; Kaser, Jakub (advisor)
The bachelor´s thesis deals with AFDD, a device that protects the low voltage electrical installations against fire caused by a serial or parallel arc fault. Although MCB and RCD can mostly disconnect the circuit when the parallel arc appears, only AFDD can detect the series arc fault. AFDD can be used only as additional protection. The theoretical part of this thesis describes the creation of electric arc, causes of house fires, and explains the principle of the Arc Fault Detection Device. The purpose of the practical part is to create real malfunctions that cause a series arc in the circuit and to test the function of AFDD. The next purpose is to repair the arc generator and to verify the function of AFDD using different materials of electrodes.
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Investigation on the Interaction between Construction Materials and Switching Arc in Low Voltage Switching Devices
Šimek, David ; Slavíček, Pavel (referee) ; Mindl,, Pavel (referee) ; Kloc, Petr (advisor)
The doctoral thesis is focused on the interaction of construction materials and the switching arc in low voltage switchgear. An issue of selected low-voltage electrical devices, electric arc in electrical devices, and its diagnostics using optical emission spectroscopy and high-speed video are discussed at the theoretical level. The main part of the work is an experimental examination of samples of selected high-performance industrial plastics. A series of tests of resistance to an electric arc were performed on these plastics. The electrical parameters of the switching process, the weight losses of the material of the quenching chambers when applying various power parameters were evaluated from the experiments. The empirical equations were determined for the calculation of the loss of individual materials in a specific configuration. Furthermore, the influence of the used material on the behavior of the electric arc in the extinguishing chamber made of these plastics was investigated. A high-speed video was recorded, the time evolution of the pressure inside the chamber, the electrical parameters of the arc, and the time-resolved evolution of the radiation spectra were measured using atomic emission spectroscopy in these measurements. The relative composition of the plasma was identified from the radiation spectra, and the time evolution of the relative contamination of the discharge area by the main contact material and the selected vapors of the used plastics was created. The last important parameter of the electric arc is its temperature, which was also calculated from the radiation spectra. A comparison of individual plastics and their applicability for applications in contact with electric arc was performed based on the obtained data.
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