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Reducing transformer inrush
Zoufalý, Marek ; Bušov, Bohuslav (referee) ; Šimek, David (advisor)
In this thesis is described the function and design of the transformer designed on ferromagnetic core, composed of transformer sheets. It is explained a transient inrush current of the transformer. In this work is inserted voltage and current waveforms, designed printed circuit board, serving to reduce the inrush current.
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Diagnostics of current path of high-current apparatuses
Váša, Lukáš ; Bušov, Bohuslav (referee) ; Šimek, David (advisor)
Bachelor’s thesis is focused on the theoretical analysis of methods of technical diagnostics with focus on high-current devices. An overview of the methods used in technical practice is elaborated. In addition, the thesis deals with the strain of current carrying path, subsequently the work focuses on the thermal stress of parts of the current carrying path and its temperature rise. Methods of diagnostics by measuring transient resistance and methods of measurement of temperatures are described and each of the methods’ advantages and disadvantages are stated. The practical part is focused on the diagnotics of the switch disconnector and the disconnector by measurement of the transient resistances of all contacts of the current carrying paths and the following measurement and evaluation of temperature rise of the components by thermal imaging camera. Adjustments to the disconnector leading to financial savings are suggested on basis of these measurements.
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Remanent magnetism of electromagnets of DC contactors
Horký, Jakub ; Píška, Jakub (referee) ; Šimek, David (advisor)
The master thesis is focused on a remanent magnetism of electromagnets of DC contactors. In the first part of the thesis deals with the formation of a magnetic field in different kinds of materials, description of their magnetization and sorting. The next part is focused on the principle and history of an electromagnet. Negative effects and remanent induction of the contactor are described in the end of the theoretical part. The second part is a practical part. First, the reaction times were measured on a pair of DC contactors. Using the obtained data, an electronic circuit was designed to minimize the difference in switching times of the given DC contactors.
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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.
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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.
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Electrodynamic forces in electrical apparatuses
Dobrovolný, Jan ; Bušov, Bohuslav (referee) ; Šimek, David (advisor)
The bachelor's thesis deals with phenomena caused by electrical current passing through electrical apparatuses current path. The main focus is on electrodynamic forces. These forces are created by the interaction of magnetic fields and significantly takes effect in case of short circuits because they rise with square of current. Electrodynamic forces are problematic especially in contacts, where it causes a repulsive force working against the contact force. A proposal of electrical apparatus must take into account these forces and must be sufficiently dimensioned. Selected apparatus - disconnector, is redrawn into 3D program SolidWorks. Electrodynamic forces on individual parts of current carrying path were calculated for short circuit current. Total balance of forces is created. The disconnector has been tested for a withstand current to verify an endurance against electrodynamic forces.
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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.
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Single stage amplifiers employing JFET and MOSFET for educational laboratory purposes
Šimek, Dominik ; Petržela, Jiří (referee) ; Langhammer, Lukáš (advisor)
Bachelor thesis deals with design and construction of measuring box for amplifiers with unipolar transistors, which will be used within laboratory classes. The point of the thesis is to create a complex instrument, which offers system used for measuring of essential characteristics of common-drain, common-source and/or common-gate amplifiers. It will help students to more easily understand principle of unipolar transistors. The printed circuit board will contain amplifier circuits with MOSFET and JFET transistors, with option to switch between measuring N-type or P-type channel transistor. The design itself is substantiated by analysis of essential theoretical properties of unipolar transistors, by numerical calculations, and simulations, which are also parts of the thesis.
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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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Design of earthing switch for diconnecter of generator
Petrič, Peter ; Šimek, David (referee) ; Bušov, Bohuslav (advisor)
This master thesis is focused on the design of earthing switch for the indoor three pole generator disconnector from IVEP, a.s. The main task of the theoretical part of the master thesis was mechanical and electrical calculations on the contact system and the design of two variants of earthing switch construction. It has been proposed two variants of earthing switch construction. The first variant included three earthing knives for each pole of earthing switch and the other variant included two earthing knives for each pole. The aim of the practical part of this diploma thesis was to create a model of the earthing switch for generator disconnector, to simulate the heating of the contact system by passing the short-circuit current and to prepare the production documentation. For modeling, calculations and simulations were used Autodesk Inventor 2018, Matlab and Ansys Workbench.
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