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Analysis and evaluation of technical systems of motor operators of circuit breakers
Hurbanič, Jakub ; Valenta, Jiří (referee) ; Dostál, Lukáš (advisor)
This bachelor thesis was created as a overview and analysis of drive systems for moulded case power circuit breakers. There si an introduction to motor operators and their possible use with remote control and use in future in name of digitalization and elektrification. Also there is listed an analysis of opertors depending on the method of installation, switching power and the operator itself i.e. electric motor or electromagnet. There is mentioned the possibilities of controll and power supply of these operators and the positions of circuit breaker. In the end a small market analysis is executed and a short chapter dealing with measurment of electric motor operator in OEZ s.r.o. company.
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Derating on the low voltage devices with a thermal trip unit
Dobrovolný, Jakub ; Vetiška, Vojtěch (referee) ; Dostál, Lukáš (advisor)
Electrical devices are secured as not to injure living creatures via electric current and damage or destroy machinery due to the effects of electric current. Circuit breaker is a device responsible for protection of an electrical circuit against damage. The main aim of thesis is the correct function of the thermal trip unit when it exposes to the thermal warming. The thermal trip unit is depended on heating of a bimetal before overcurrent flow. The goal of thesis is temperature and voltage drop profile from measured values. Verification of the measurement is done in SolidWorks Flow Simulation software. According to simulations are determined currents for correct function of the thermal trip unit in different temperatures of an environment. The most important result of the thesis is correct setting of the operating current in the circuit breaker.
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Optimization of the cooling of induction machines
Halfar, Ivo ; Dostál, Lukáš (referee) ; Janda, Marcel (advisor)
This master‘s thesis deals with problems of optimization of cooling in electrical machines. This work includes introduction to the theory of mathematical optimization and brief introduction to optimization problems. This thesis deals with using of program Ansys Workbench for the thermal analysis in electrical machines and optimization of their cooling. Thesis contains thermal analyse of specific asynchronous motor with the squirrel cage and optimization of its cooling.
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Vibrodiagnostics of induction motor
Mašin, Dominik ; Dostál, Lukáš (referee) ; Janda, Marcel (advisor)
This thesis is dealing with measuring and evaluation of vibration signal. Vibration measurement is one of the most important operation for correct and fluent machinery service, not only from economical point of view but also because of security. Status monitoring of electric machine is a key to detect damaged parts and it is giving us an opportunity to avoid unexpected outages and failures in production. My work describes basic concepts and principals of vibration measurement. Asynchronous motor measurement and its evaluation is performed in practical part.
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Rerating on the low voltage devices with a thermal trip unit
Trubák, Vojtěch ; Valenta, Jiří (referee) ; Dostál, Lukáš (advisor)
This work is about bimetal trip unit used in circuit breakers. It focuses on how ambient temperature affects function of this tripping unit. In second chapter of this work, there are described thermal and dynamic effects of electric current. You can find there equations for calculation of temperature rise caused by electric current, its max temperature change and its process, also equations describing force, caused by electric current. In third chapter is short introduction of circuit breakers. There is description of their function, classification and construction. Finally there is description of residual current device. Fourth chapter of this work is focused on bimetals. There is described their function principle, ways of manufacture, used materials and its tripping characteristic. In fifth chapter, the circuit breaker 3VA12 is introduced, its electrical characteristics and its applications. Also, there is described principal of bimetal application as thermal trip unit. Sixth chapter is about procedure used to create model in CAD program Solidworks. You can find there individual pieces of current path and its addons connected together and forming model of circuit breaker. There are also showed modifications of the model, using thermal and conduction resistances. Last chapter is dedicated to results of rerating. There is final table showing correction koeficients of rated operational current and their comparison to real ones.
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Applying SolidWorks Flow Simulation for cooling system of the power converter
Matoušek, Patrik ; Vetiška, Vojtěch (referee) ; Dostál, Lukáš (advisor)
Thesis deals with the issue of cooling power converters. It describes the disposition of power converter M50, produced by ELCOM, a.s., and the distribution and origin of heat losses in the converter. The thesis then describes the process of creating a 3D CAD model of the converter in Solidworks and the procedure for heat simulation of the converter in default state and with cooling fan failures using Solidworks Flow Simulation. The thesis then evaluates the results of these simulations, and on their basis it suggests possible improvements in the design of converter‘s cooling system. These improvements are then evaluated in further simulations. The thesis then describes the verification of performed simulations by comparison with a temperature-rise test.
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Affecting the function of thermal release of circuit-breakers for different connection systems
Lednický, Ján ; Vetiška, Vojtěch (referee) ; Dostál, Lukáš (advisor)
Right function of securing electrical installations is one of the most important factors preventing people, animals and electrical devices themselves from being electrocuted. Circuit breakers with an overcurrent tripping unit work with bimetal. When the bimetal is warmed up enough, it causes disconnection of circuit. This prevents people and animals from being harmed. To make overcurrent tripping unit work the right way, we have to minimise unnecessary disfunction factors caused by thermal thaw and Joule´s heat. This thesis is aimed at gaining general knowledge of heat transmission and transition of electrical current into heat. There are going to be made temperature-rise curves using all available connection sets to evaluate the impact of each one on the tripping unit. Then, a temperature profile of the circuit breaker will be made using a simulation made using SoildWorks Flow Simulation program. Finally, critical places of the current path will be observed.
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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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Analysis of effect of the switching system of low voltage breaker on the thermal tripping unit
Liščák, Jiří ; Šimek, David (referee) ; Dostál, Lukáš (advisor)
Main aims of this master’s thesis are executing measurements and simulations on low voltage circuit breaker and analyzing effect of the switching mechanism on the thermal tripping unit. There are two programs used for simulations in this thesis ANSYS and SolidWorks Flow Simulation. As another part of the thesis were done two types of tests. First was electrical durability test and second one was warming test. In this thesis were measured values of warming on whole current path not only on thermal tripping unit.
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