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Analysis of effects of short-circuit current in switchgear cabinet
Prokop, Jan ; Bušov, Bohuslav (referee) ; Valenta, Jiří (advisor)
The work is focusing on dynamic effects of short-circuit currents, more precisely dynamic effects of short-circuit currents on switchgear cabinet (terminal box). The work was designated to a concrete construction type of two switchgear cabinets located on rotating machines via company Siemens Electric Machines Drásov s.r.o.. The switchgear cabinets are designed for non-explosive environment where the air is used as an insulating medium. The task was to determine how the device will behave during the three-phase short-circuit and three-phase short-circuit with earth/ground connection. The following programs were used for the calculations and simulations: Ansoft Maxwell 16.0, Ansoft Maxwell 2015 and ANSYS Workbench 16.0. By using these programs the effects of forces which acts on current paths in cabinet caused by the passage of short-circuit current were simulated, statically and also dynamically. Further the effects of pressure acting on cabinet frame during the arc short-circuit have been statically and dynamically simulated. All the results are summarized in the conclusion. Conclusion also contains the final evaluation of the functionality of both switchgear cabinets.
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Analysis of a bimetal release
Zelenka, Michal ; Augusta, Zbyněk (referee) ; Valenta, Jiří (advisor)
This master‘s thesis deals with the thermal overload trip unit in automatically operated electrical switching devices. The first part of this thesis serves as a basis for a design of thermostatic bimetal element in electrical switching device. The thesis presents important parameters and calculation principles needed for the design of bimetal element. The thesis further describes the operating principle of thermal trip unit and its possible design solutions. The main part is devoted to analytical calculation and measurement of specific thermostatic bimetal type contained in thermal trip unit of molded case circuit breaker. It is measurement of force and deflection, depending on temperature change. In the next part a numerical model of the bimetallic strip was created and its deflection was simulated. The analytical results are compared with the measured and simulated results at the end of the thesis.
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Apparatus for parameter identification instrument voltage transformer
Tománek, Drahomír ; Valenta, Jiří (referee) ; Dohnal, Petr (advisor)
This master thesis describes the design and production of devices for identifying the parameters of the instrument transformer. Work is divided into seven chapters. The first part focuses on the production of instrument voltage transformer. The next section describes the measurement and description of the parameters of instrument voltage transformer and design of printed circuit boards. Another section is devoted to a program for measuring card. The final part is manufactured and tested unit conducted the first test measurements.
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The temperature profile of the power switching device of low voltage for different operating conditions
Mejzlík, Tomáš ; Valenta, Jiří (referee) ; Dostál, Lukáš (advisor)
The heat generated in a circuit breaker can be transmitted in two ways: Either through metal parts of current path to conductors outside of device or through plastic parts or air of chassis. The accuracy of the simulation depends on the accuracy of the 3D model and all his parts and it also depends on precise definition of materials with precise definition of electrical and thermal parameters. Electrical circuit breaker has various source of the heat which results in raising temperature of the device above the level of environment. Heat sources are: 1) Joule’s loss of the circuit breaker current path. 2) Heat loss in a bimetal, which is used for thermal release. 3) Resistivity of contacts. This thesis deals with static state of thermal analysis so the sources do not include transient heat source for switching OFF and switching ON. Electrical circuit breakers are made in smaller and smaller forms however their electrical parameters are not decreasing with size. There is logical conclusion that there is more heat on the same unit size which makes thermal analysis of circuit breaker one of the most important part of development.
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Calculation of electrodynamic forces in 1600 A circuit breaker
Musil, Pavel ; Bušov, Bohuslav (referee) ; Valenta, Jiří (advisor)
The thesis is focused on the calculation of electrodynamic forces that counterwork on moving contacts of compact circuit breaker BL1600 from the company OEZ Letohrad. The thesis is divided into separates chapters that build on themselves. In the introduction the reason why we deal with calculation of dynamic forces and structural arrangement of current carrying path is described. In the following chapter there is a theoretical analysis of electrodynamic forces that conterwork on individual parts of circuit breaker´s element. The third part is devoted to structural arrangement of the circuit breaker BL1600. In this part we can find an example of using the circuit broker Modeion in practice. Two next chaptures deal with adjustment of the model of current carrying path which then serves for the calculation of electrodynamic forces. The rest of the thesis is devoted to my own calculations. These calculations are mainly stationary where we try to find the forces that conterwork on the contacts in a steady current and in a point in time. There are also dynamics calculation when we can watch the forces that counterwork on contacts in a certain time interval. The last chapter is devoted to a stationary calculation of forces that counterwork on the electrical arc which arises while turning the short-circuit current off. The obtained results are evaluated in partial conclusions of this thesis.
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Calculation of DC electromagnet and its experimental verification
Steidl, Adam ; Vetiška, Vojtěch (referee) ; Valenta, Jiří (advisor)
Content of this thesis deals with electromagnets as operating elements in electric machines. Thesis is divided in two main parts, theoretical and practical. The theoretical part describes electromagnets as an electric machine, usage of electromagnets in electrical devices as operating element. Electromagnets are further divided in groups on the basis of different criteria. Next, the theory of electromagnetic fields and methods of assesment of static pull and dynamic characteristics are described. Construction and function analysis of researched type of electromagnet from OEZ company with permanent magnets, which serves as trigger in compact circuit breaker, is also included in this part. Practical part includes measurement of force quantities of an electromagnet in different operating states and its evaluation. For analysis of dynamic quantities with finite element method was created suitable three-dimensional model of electromgnet. Model is used for simulation ofdifferent operating states.The last part describes measurement of dynamic characteristics of the electromganetic system. This part is closed with comparation of results.
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Calculation of DC electromagnet and its experimental verification
Steidl, Adam ; Vetiška, Vojtěch (referee) ; Valenta, Jiří (advisor)
Content of this thesis deals with electromagnets as operating elements in electric machines. Thesis is divided in two main parts, theoretical and practical. The theoretical part describes electromagnets as electric machine , usage of electromagnets in electrical devices as operating element. Electromagnets are further divided in groups on basis of different criteria. Next, the theory of electromagnetic fields and methods of assesment of static pull and dynamic characteristics is described. Construction and function analysis of researched electromagnet with permanent magnets, which serves as trigger in compact circuit breaker, is also included in this part. Practical part includes measurement of force quantities of researched electromagnet in different operating states an its evaluation. For analysis of dynamic quantities with finite element method were created two-dimensional and three-dimensional models. Evaluation of analysis follows. After that is described simplified design of electromagnet, based onoperating states of researched electromagnet. This part is closed with comparation between results of analysis and designed values of electromagnets.
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CVVOZE Short circuit lab description
Brdečko, Aleš ; Valenta, Jiří (referee) ; Dohnal, Petr (advisor)
This diploma thesis deals with the analysis and description of high power laboratory CVVOZE. In the text we can find a description of the individual elements high power laboratory stating their parameters and their analysis from the perspective of impedance. The practical concern of this work is the creation of program for calculating the adjustment burdens and creating utilities helpful for operation and interpretation of laboratory function laity and technical employees.
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3D CAD systems used in the field of electrical apparatuses
Makki, Zbyněk ; Krejčí, Jan (referee) ; Valenta, Jiří (advisor)
The aim of this project is to describe and compare individual 3D CAD systems and data format used in the area of construction and technical support in agreement with factual needs of project submitter company OEZ, Ltd. Fulfilment of 3D CAD systems background research which are used in the area of design of the electrical switchboards LV. Description of the main possibilities, that the particular system offers. Supported data format for export and import are mentioned too.
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