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Lead-acid battery charger with a pulse converter
Mihályi, Róbert ; Martiš, Jan (referee) ; Vorel, Pavel (advisor)
This master´s thesis discusses on complete designing of a lead-acid accumulator charger. Charger operates with the principle of a two-switch forward converter. It contains the design and manufacturing of all the proposed winding subcomponents, the semiconductor components, the control circuit board and the power circuit board. This thesis includes also the design and description of the individual parts of the power circuit and control circuit. The revival of the charger, including a description of the individual adjustments that were necessary for proper and reliable operation is also in the content. This thesis contains too a series of measurement performed to verify the correct function of the charger.
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Application of Ultracapacitors in Traffic Systems
Kalina, Emil ; Vorel, Pavel (advisor)
The work deals with relatively new components allowing electric energy accumulation – ultracapacitors. It focuses on their application in traffic systems – in independent electric vehicles. Design and verification of a system with ultracapacitor and DC/DC adaptive converter was done. Control of the adaptive converter modifies very positively the time wafeform of the traction accumulator current during the drive cycle. The designed connection of ultracapacitor and DC/DC converter implemented in the drive structure of experimental electric vehicle with induction machine contributes to increment the action radius of the vehicle by 16% (determined by experimental verification). This result was achived particularly by limitation of traction accumulator current peaks, And by more effective storage of energy gained by recuperative braking of the vehicle as well. The core of the system is a control of the adaptive converter in order to provide an active filtration of the accumulator’s current to its long-period mean value, i.e. elimination of current (power) peaks. These are caused by acceleration from non-zero initial vehicle speed or by recuperative braking. This is done by a subsidiary current loop. The converter has a superior voltage regulation loop, which sets in long-time period the voltage of ultracapacitors to the proper value – indirectly dependent on the speed of the vehicle. This ensures the appropriate energy management of the ultracapacitor. In the following, properties of test set of ultracapacitors were verified. Finally, methods of suppression of capacity variability influence in series connection of these components were compiled and critically reviewed.
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DC/DC converter 2,5kW/1500A for resistive heating of iron components
Martiš, Jan ; Knobloch, Jan (referee) ; Vorel, Pavel (advisor)
This thesis deals with the design and construction of a single-phase switching power supply, which is intended for direct resistive heating of iron components. The power supply is especially intended for resistive heating of horse-shoes. The supply is able to deliver an output current of up to 1500 A at a power of up to 2500 W. The first part of this work deals with the design of individual parts of the unit, the second part is focused on construction and testing of the supply and the last part contains technical documentation. The power supply was successfully tested and the required output parameters were met. However some problems do exist, especially with overheating of the output rectifier and with contacting the heated component to the output leads of the supply. These problems will be discussed in the work. The power supply can be used as an alternative solution to classic means of iron heating. The methods and ideas presented in this work can be applied in a design of a similar power supply with high output current, but most of the design rules are valid generally for the given topology.
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Low-frequency Amplifiers
Doležel, Tomáš ; Vorel, Pavel (referee) ; Patočka, Miroslav (advisor)
The bachelor thesis deals with the involvement of the audio amplifier, design printed circuit boards, implementation and verification of measuring amplifiers. The proposed amplifier has an output of 100 W at nominal load 4 at a supply voltage of ± 30 V. The bandwidth of the amplifier is 550 kHz.
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Electric bike with a combustion-engine-powered generator
Mička, Dominik ; Červinka, Dalibor (referee) ; Vorel, Pavel (advisor)
A conceptual design and realization of a motor bike using combustion engine and electrical power transfer is the objective of this master´s thesis. Control strategy that allows combustion engine to reach maximal efficiency cooperating with wide range speed and torque operating area electromotor was created. All function blocks were realized. Also hardware of all needed parts was developed. The last part was a design and debugging of control software. Finally the functionality was documented by test drives and measurements.
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Switching Power Supply with Planar Transformer
Pawlas, Andrzej ; Vorel, Pavel (referee) ; Šebesta, Jiří (advisor)
This master's thesis describes the development of switching power supply with planar transformer. Deals with selection of a suitable integrated circuit together with the topology, a purchase of prototype for the reference measurements and debugging its own power supply. Further design and implementation of planar transformer and in the final implementation, debugging, and measurment's its own prototype. Power supply was fully functional and reached the expected parameters.
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Efficiency Improvement and Optimization of High Power Switching Converters
Martiš, Jan ; Dudrik,, Jaroslav (referee) ; Peroutka,, Zdeněk (referee) ; Vorel, Pavel (advisor)
This thesis focuses on optimization and increasing the efficiency of high-power DC/DC switching converters with transformer (switching power supplies). The work focuses mainly on using converters with flyback topology for high power, even though it is a common belief that this type of converter is not suitable for high power. This topology was selected because of potentially better achievable parameters, especially the efficiency, in comparison to a commonly used forward converter – in a flyback converter, losses are produced only in one magnetic component (transformer) in contrast to two components (transformer and inductor) in the forward converter. Compared to resonant and quasi-resonant converters, the flyback converter is easily controllable in the whole output voltage and current range. To make the flyback converter favorable for a high-power use, some innovative circuit modifications were made and modern semiconductor and passive components were used. Theoretical part of the work deals with efficiency optimization of the flyback converter, based on analytical solution. Operating parameters of the converter – switching frequency and parameters of the transformer (flux density and numbers of turns) are commonly only guessed or chosen from experience. The objective of this part is a mathematically exact determination of these parameters to achieve lowest total losses of the converter for given input parameters. In a certain case, it was possible to obtain the final solution analytically, in other cases the final solution step had to be done with a help of software. A prototype of a 12-kW switching power supply with a flyback converter was constructed to validate the proposed solutions and methods. The power supply fits into a space of only 33x33x16 cm. Modern semiconductors based on the silicon-carbide (SiC) technology (MOS-FET transistors and diodes) were used. After bringing the converter to a full-power operation, an efficiency of 96.8 % of the DC/DC converter was measured. High efficiency was obtained for a wide range of output parameters. A certain comparison with a forward converter with the same output parameters is done in the work. Not only from an efficiency point of view, the flyback converter seems very perspective.
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Laboratory test equipment for IGBT transistors
Chvátlina, Pavel ; Vorel, Pavel (referee) ; Patočka, Miroslav (advisor)
This master’s thesis describes the function and realization of the laboratory test equipment designed for measuring and analysing of collector current iC and voltage uCE courses during the opening and closing process of a power IGBT transistor. The opening and closing times toff and ton of the new power transistor IGBT are changing in the range from tenths to the ones s, so the reading of current iC and voltage uCE proceeds in a very short time. The measuring circuit of this test equipment is based on a short-time discharging of a condenser battery to the inductive load over the measured transistor. Consequently it is possible to replace the power supply whose maximum output power would otherwise have to be in the range of ones MW. In the final part of this thesis there are described properties and design of a high-frequency sensor with the Rogowski coil, which can be used for reading collector current course during opening and closing time of the measured transistor IGBT. Collector current iC and voltage uCE courses can be analysed with a storage oscilloscope.
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Drivers for power switching transistors GaN MOSFET
Fiala, Zbyněk ; Pazdera, Ivo (referee) ; Vorel, Pavel (advisor)
The thesis describes the procedure during the proposal of the driver circuits for the GaN MOSFET transistors, which are known for their fast switching especially. In the first instance of this thesis the issue of GaN MOSFET transistors is described and also the thesis describes the different types of MOSFET transistors in the way of their electrical and mechanical attributes. The specific type driver circuit is stated in the thesis, which was selected in the semestral thesis. For this circuit the boost converter with an output power 600W and high switching frequency 800kHz was proposed as an attempt measurement circuit. This boost converter was measured after its construction was done. The waveforms captured by the oscilloscope are commented also. In the conclusion the assessment is done about this new technology of power switching transistors.
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