National Repository of Grey Literature 35 records found  previous11 - 20nextend  jump to record: Search took 0.00 seconds. 
Electric fault arc detection in LV network
Dubský, Martin ; Fencl, Jiří (referee) ; Dostál, Lukáš (advisor)
This thesis deals with arc detection using AFDD. Here is explained the general theory of electric arc. It also describes the principle of operation of the AFDD device, a specific type of instrument from OEZ s.r.o. and describe the test procedure for this instrument according to the technical standard. In the practical part, selected tests are performed and verified the function of the AFDD device in the event of a disturbance electric arc in the circuit.
Electric arc heating
Kahoun, Karel ; Bušov, Bohuslav (referee) ; Šimek, David (advisor)
This bachelor's thesis deals with an arc heating in industrial applications. In this paper, there is described laboratory equipment for the generation of electric arc. Thesis also contains theoretical analysis of heat transfer from the arc to nearby object. The main part of the thesis is devoted to experimental measurement of heat transfer from the arc to the nearby object in relation to the electrical power and the surface finish of the object.
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.
Electric arc heating
Kahoun, Karel ; Zelenka, Michal (referee) ; Šimek, David (advisor)
This bachelor's thesis deals with an arc heating in industrial applications. In this paper, there is described laboratory equipment for the generation of electric arc. Thesis also contains theoretical analysis of heat transfer from the arc to nearby object. The main part of the thesis is devoted to experimental measurement of heat transfer from the arc to the nearby object in relation to the electrical power and the surface finish of the object.
Derating on the low voltage devices with a thermal trip unit
Dobrovolný, Jakub ; Vetiška, Vojtěch (referee) ; Dostál, Lukáš (advisor)
Electrical devices are secured as not to injure living creatures via electric current and damage or destroy machinery due to the effects of electric current. Circuit breaker is a device responsible for protection of an electrical circuit against damage. The main aim of thesis is the correct function of the thermal trip unit when it exposes to the thermal warming. The thermal trip unit is depended on heating of a bimetal before overcurrent flow. The goal of thesis is temperature and voltage drop profile from measured values. Verification of the measurement is done in SolidWorks Flow Simulation software. According to simulations are determined currents for correct function of the thermal trip unit in different temperatures of an environment. The most important result of the thesis is correct setting of the operating current in the circuit breaker.
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.
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.
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.
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.
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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