|
|
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.
|
|
|
Mathematical model of RCCB sensitive to pulsating direct currents
Kaser, Jakub ; Dostál, Lukáš (referee) ; Valenta, Jiří (advisor)
This Thesis deals with problematics of residual current circuit breaker and its eventual operation malfunction due to DC components. There are magnetic phenomena described in details which occur inside of the apparatus. Consequently, there is proposed a mathematical model of the circuit breaker in Simulink program. The comparison of B-H curves of transformer core is composed and achieved results are incorporated into the proposed model in order to verify a correct operation of the circuit breaker and its reaction to different conditions. The verification of the symmetry of the magnetic field in residual current circuit breaker in Ansys Maxwell program is also a part of the study.
|
|
|
Switching arc diagnostics in DC contactor
Píška, Jakub ; Kloc, Petr (referee) ; Valenta, Jiří (advisor)
Cílem této diplomové práce bylo provést diagnostiku vysokonapěťového stejnosměrného stykače se zaměřením na zpětnou komutaci a lepení oblouku, navrhnout a ověřit úpravy, které odstraní tyto negativní jevy. Měření obloukového napětí, tlaku a pomocí rychlokamery byly použity při diagnostice těchto jevů. Změny na arcrunnerech a jhu magnetického obvodu byly využity při jejich odstraňování. Úpravy na arcrunneru zmenšily skokové nárusty délky oblouku a úpravy na jhu navýšily sílu na oblouk mezi rozevírajícími se kontakty. Navrhnuté změny na stykači snížily časovou ztrátu v důsledku zpětné komutace, a tak zkrátily čas přenosu oblouku.
|
|
|
Analysis of electrodynamic forces in electrcal apparatus
Dobrovolný, Jan ; Valenta, Jiří (referee) ; Šimek, David (advisor)
The master thesis deals with the phenomena called electro-dynamic force in the electrical apparatus. Nowadays, there are high requirements for electrical devices. The devices and especially their contacts are subject to high demands on reliability, reliability and mechanical durability. The electro-dynamic forces caused by the passage of electric current mechanically deform the current path. The design of the electrical apparatus must take these forces into account. Equations for electro-dynamic forces calculation are presented. In master thesis, individual parts of the current path are derived and described. Various configurations and designs of the current path are solved. The thesis also deals with the issue of forces in electrical contacts. Individual theoretical equations are then applied to a particular disconnector QAK, made by company IVEP, a.s. Parts of the disconnector were redrawn into 3D program SolidWorks. The model was analysed in program ANSYS Maxwell. The thesis compares the achieved results of analytical equations and numerical simulations.
|
|
|
Development of DC arc quenching chamber
Černohorský, Petr ; Valenta, Jiří (referee) ; Šimek, David (advisor)
Seminar thesis focuses on the issues about quenching the electric direct arc by the quanching system. Teoretical part deals with action about quanching the direct arc and with another actions which happens in direc discharge. There is described proposal and construction of the insulating quenching system. Than chamber was testing in high voltage laboratory and the results from testing was evaluated.
|
|
|
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.
|
|
|
Residual current device behavior under switching of non-sinusoidal residual currents
Horký, Jakub ; Dostál, Lukáš (referee) ; Valenta, Jiří (advisor)
This bachelor deals with behaviour of a residual-current device during disconnection non-sinusoidal residual current. In the first, theoretical part, basic characteristics and properties of electrical devices are described. Attention is devoted to residual-current device, its structural part, parameters and types. Afterwards, there are described normative requirements of the residual-current device type A in the course of tests. The second part is a practical part. The residual-current device is subjected to residual currents with direct current components (according to the standard), thereby it is checked if it works correctly, it means, if the device is capable of being cut off, At the end of the bachelor, where is a sample laboratory task that demonstrates a check the behavior of the residual-current device at switching off the non-sinusoidal current.
|
|
|
Calculation of electrodynamic forces acting on current path of a switching device
Benčo, Tomáš ; Bušov, Bohuslav (referee) ; Valenta, Jiří (advisor)
The master thesis is focused on the calculation of electrodynamic forces acting on the contacts of the moulded case circuit breaker Siemens 3VA5 from OEZ Letohrad. This work is divided into ten chapters. In the introductory chapter it is described why it is important to deal with the calculation of the electrodynamic forces and the design of the current path. The second chapter describes the problem of the origin and effect of electrodynamic forces on individual parts of the electrical device. The third chapter describes the parameters, properties and design of the 3VA5 Siemens circuit breaker. The fourth chapter describes the Finite Element Methods. The fifth chapter describes how to create a 3D current path model in Solidworks. The sixth to ninth chapter is focused on the stationary calculation of moments in the program Ansys Maxwell by means of Magnetostatic Analysis and on the calculation of the total repulsive force between contacts with the influence of ferromagnetic materials. The last chapter is focused on dynamic calculation of moments and forces acting on contacts in a certain time interval.
|
|
|
Evaluation of pressure conditions in the quenching chamber of low-voltage device
Nevrzal, Filip ; Vávra, Daniel (referee) ; Valenta, Jiří (advisor)
In this master’s thesis there is firstly conducted research about pressure measurement. Next there is mathematical description of thermodynamic conditions in used testing chamber by using magnetohydrodynamic and Maxwell equations. Next chapter deals with testing chamber itself, more precisely with function, model and changes done to it. In practical part there are data measured by used sensors, which are also closer described in this chapter. In next chapter there is comparison of reaction times of used sensors and their frequency specters, obtaining using fast Fourier transformation. Second to last chapter introduces very measurement on the real device and in the last chapter these data are analyzed and more closely described.
|
|
|
Contact erosion of switching devices
Píška, Jakub ; Šimek, David (referee) ; Valenta, Jiří (advisor)
This bachelor thesis deals with the erosion of contacts, as one of the negative phenomena affecting contacts of switchgears. In its first part, it briefly summarizes the other negative influences that must be considered when designing switching devices. In the following part, the physical mechanism of erosion and the primary criterion of assessment - weight loss are approached. The last and main part of the work deals with design of the contact system for comparing this loss for for frequently used materials and testing on a real switchgear. After the tests, the results were analyzed primarily from the perspective of ignition angles, the polarities of the current pulse and the current flowing through the arc. Taking into account the influence of the material composition, the size of the contacts and the presence of the arc-runner.
|
guest ::
RSS feed.