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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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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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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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Plasma speaker - audio modulated electric arc
Klein, Ondřej ; Červinka, Dalibor (referee) ; Martiš, Jan (advisor)
The bachelor thesis deals with design and realization of electric arc modulated by audio signal. It is also known as plasma speaker. Absence of any mechanical components gives membranless speaker no frequency limitation. The design consist of single circuits as power sources for power and control section, control electronics, which modulates the signal, and power section, which reproduce signal in form of sound.
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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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Fibre optic tapering and shaping methods for special applications
Hruška, Andrej ; Jelínek, Michal (referee) ; Mikel, Břetislav (advisor)
The thesis deals with the tapering of optical fibres and the shaping of their ends. The thesis describes the fibre tapering and shaping methods and compares them in terms of advantages and disadvantages. It mainly focuses on methods using electric arc, flame and chemical etching. The practical part of the work describes the methodology of fibre tapering for 125 m, 400 m and 1000 m fibre diameters and the methodology of fibre end shaping for 400 m and 1000 m fibre diameters.
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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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Temporal Development Of Relative Ablation Of Plastics In Miniature Circuit Breaker During Switching Process
Simek, David
The paper is focused on an ablation of plastic materials in contact with an electric arc inside the electrical apparatus during the switching process. It is possible to obtain temporal development using method based on optical emission spectroscopy. The emission spectra were taken during the switching process. The hydrogen alpha spectral line of Balmer series was used as an indicator for evaluating of plastics ablation. Complications connected with the measurements are discussed. The main part of the paper deals with a temporal development of relative concentration of a hydrogen in plasma inside the miniature circuit breaker. Atomic spectral lines database of National Institute of Standards and Technology was used as a spectral data source for evaluation.
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