National Repository of Grey Literature 35 records found  1 - 10nextend  jump to record: Search took 0.01 seconds. 
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.
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.
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.
Thermal spray by electric arc
Eliáš, Vojtěch ; Sigmund, Marian (referee) ; Kubíček, Jaroslav (advisor)
This thesis deals with the issue of thermal spraying by means of an electric arc. First of all, a theoretical part is processed using a literary study dealing with corrosion and thermal spraying technology. The experimental part contains a description of the technological procedure and evaluation of four thermally sprayed samples. Zinacor 850, consisting of 85% zinc and 15% aluminum, was used as a coating. The evaluation involves measurements of thickness, adhesion and roughness as well as the macro-structural analysis of the coating. Two samples showed unusually low adhesion, and all samples also had a large fluctuation of the measured thicknesses. This was also confirmed by the macro-structural analysis, which showed that the sample with low adhesion also had high porosity. These defects may have multiple causes, but the recommendation for further practice is to reduce the spraying distance from the base material.
Investigation of correlation between arc voltage and arc movement
Szotkowski, Šimon ; Valenta, Jiří (referee) ; Kloc, Petr (advisor)
The electric arc burns in an ionized gas and is divided into AC and DC arc according to the power supply. The electric arc is conductive, so to turn off the electric circuit, the arc must be extinguished as soon as possible. Arc breakers are used to extinguish the arc. Arc breaker must be designed to withstand the increased pressures and temperatures caused by the arc. The purpose of the bachelor's thesis was to design and construct a arc breaker with the possibility of monitoring the movement of the arc with a high-speed camera. From the measured data, the dependence between the arc voltage and the movement of the arc root was determined by correlation analysis. Correlation analysis is used to calculate the possible existence of a dependence between two quantities with the correlation coefficient and testing.
Investigation of the durability of low voltage switching apparatuses construction parts
Dalecký, Jan ; Dostál, Lukáš (referee) ; Šimek, David (advisor)
This thesis deals with study of durability of low voltage switching devices components. It describes components of circuit breaker and low voltage contactor and contains function models of these devices in various states. Based on model analysis, components that can get worn, damaged or destroyed were selected. Further practical experiments on two samples of circuit breakers from different manufacturers were executed to verify their technical parameters and parts durability. Failure of some components can cause switching device to malfunction.
A Sample ARC Detector Panel
Pala, Lukáš ; Valenta, Jiří (referee) ; Kadlec, Radim (advisor)
In the introduction an electric arcs creation in low voltage networks is discussed, followed by evaluation of verification measurements with AFDD. A serial arc generator is designed in accordance with easy manipulation and low maintenance requirements. Technological solution for safe fault simulation is described similarly as particular function sections of demonstration panel. Schematic diagrams of power and electronic circuits are attached.
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.
Design and realisation of laboratory task for AFDD evaluation
Kaser, Jakub ; Bušov, Bohuslav (referee) ; Valenta, Jiří (advisor)
AFDD, electric arc, product for student, laboratory work
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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