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Power Inverter Online Diagnostics
Knobloch, Jan ; Chlebiš,, Petr (referee) ; Drábek,, Pavel (referee) ; Klíma, Bohumil (advisor)
This doctoral thesis focuses on the problems of IGBT failure prediction in pulse converters using measurable changes of selected parameters (so--called trending variables) being influenced of transistor degradation during aging. Firstly the state--of--the--art in this field is presented in the dizertation. The description of designed and constructed automated measurement stand follows, enabling monitoring and recording of switching processes during accelerated aging. Further the problems of high--bandwidth measurement of electrical quantities during IGBT switching are described. Especially the problems of current sensing are analyzed and the most suitable sensor is selected. The data recorded using the developed apparatus served to identify potential trending variables allowing the failure prediction. Here the dependence of trending variables on aging and on parasitic influences (current, temperature, voltage) had to be distinguished. Finally the evaluation of trending variables is performed. Their insignificant sensitivity on accelerated aging is shown which complicates their practical implementation for the purpose of failure prediction.
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Draft sources 1000A AC current sensors for calibration
Klimeš, Jan ; Vetiška, Vojtěch (referee) ; Dohnal, Petr (advisor)
This bachelor thesis deals with design and construction of device for precise measurement of 1000 A alternate current. This thesis theoretically discusses the possibilities of conventional solutions, such as current transformers, as well as modern methods in the form of current sensors. The output of this thesis is a solution of problems with accuracy and discussion of other possible ways to reduce systematic error. The thesis discusses structure of the current transformer, the digitalizing of the signal and its usage as an input for engineering units. The device is then tested for final accuracy.
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Contactless Wiegand Effect DC and AC current sensor
Štefánek, Martin ; Szabó, Zoltán (referee) ; Kubásek, Radek (advisor)
The paper describes the types of magnetic sensors, which are used for measuring magnetic fields. The document is divided into chapters, which describe Wiegandův sensor and its implementation into the magnetic sensor in this document is designed magnetic circuit design for this sensor. The work evaluates the progress in the design of contactless ammeter that measures AC and DC current via Wiegand effect. Experimental verification principle and its function for DC current is described in the penultimate chapter.
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Measuring and recordes electrical electrical quantities
Vít, Tomáš ; Čejka, Miloslav (referee) ; Havlíková, Marie (advisor)
The aim of this Bachelor's thesis is the design and realisation of a device able to measure and record electrical quantities - voltage, current and resistance. The part of design is a theoretical description of measurement methods with the selection of suitable components. Based on these components is designed hardware design of the device, followed by its practical assembly. The final device is able to be measured electric variables at centain intervals, which are then stored on the SD card. The final element is the CSV file containing the measured data and time of each measurement.
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Dual channel bench power supply
Stehlík, Ota ; Brančík, Lubomír (referee) ; Kubíček, Michal (advisor)
The aim of this thesis is to design and construct a two-channel bench power supply with variable output voltage in range from 0 V to 25 V with a maximum output current of 2 A. At the beginning of the thesis a general principles of power supplies are summarized. In the following section a detailed design description and simulation results of the main power supply are given. Afterwards, the design and description of auxiliary power supply with electronically controlled fan is presented. Finally, measured characteristics of the bench power supply are given.
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Wireless Telemetry System for RC Model
Čamaj, Peter ; Prokopec, Jan (referee) ; Šebesta, Jiří (advisor)
This project deals with design and realization of wireless telemetry system, which is special used in model of plane on remote control. It solves software and hardware realization of the telemetry system, which is able to wirelessly transmit the measured cockpit values, which are clearly displayed on LCD and also represented by sound.
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Current sensing with Hall-effect sensors
Štindl, Daniel ; Kovář, Jan (referee) ; Šotner, Roman (advisor)
This master's thesis deals with integrated Hall-effect current sensors. The thesis contains summary of manufacturers of current sensors suitable for low current measurement and comparison of their important parameters. Next objective of the thesis is a design of test board used for evaluation of temperature depedent accuracy of several sensors simultaneously. The device can be connected with PC through USB interface for saving measured values or automated control with other instruments.
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Coaxial multiplexer for automatic measurement of AC current
Boštík, Ondřej ; Klusáček, Stanislav (referee) ; Havlíková, Marie (advisor)
Master’s thesis in the theoretical part deals with literature review on the topic of measurement errors and measurement uncertainties. The practical part deals with the simulation of additional capacitive and resistive load on the amplitude and phase error during shunts based measurement. For this simulation is used mathematical apparatus of cascade matrix of two-ports and their connections. For the actual simulation is used script for MATLAB. Furthermore, the work deals with the design of voltage follower to eliminate simulated errors and its practical realization. The last part deals with the design of the coaxial multiplexer for switching current shunts developed in the Czech Metrological Institute in Brno.
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Current Transformers and Current Sensors Confrontation
Popek, Jiří ; Bok, Jaromír (referee) ; Topolánek, David (advisor)
Current transformers and current sensors are devices which are mostly used for current measurement in high voltage systems. This devices transform measured currents to range which are workable for measurement and protection devices. Current transformers have been using for current measurement since electric system was built. Current sensors are using for measurement after applying digital devices in their secondary circuits. Theoretical part includes fourth and fifth chapter. These chapters contain construction analysis and characteristic points for both devices. Practical part is in chapter six. This chapter consists results from laboratory measurement. Results are used for verification with theoretical part of the thesis. Accuracy class in nominal range and progress for measurement error in overcurrent range was verified for tested devices. Conclusion of this thesis comparing properties and summarises results from laboratory measurement.
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Accurate AC Current Measurements
Nováková Zachovalová, Věra ; Vrabček,, Peter (referee) ; Draxler,, Karel (referee) ; Beneš, Petr (advisor)
In recent years precision measurement of alternating currents goes through large progress especially because of improvements in metrology of electric power, which is related to reduction of electricity consumption. Therefore, more precise measurement of electric energy, power and power quality is required. Measurement range is extending and number of measured frequency points is growing up to 100 kHz. Development of current to voltage transducer with normalized output voltage (0,5 V - 1 V) is in progress because of their easy integration in different measuring systems.. From big area of alternating current metrology this dissertation focuses on development of improved cage shunts for measurement of alternating currents in range 10 mA - 100 A, 10 Hz - 100 kHz. Main objective of this dissertation is to develop theoretical model of existing cage shunts, which will assist design of new improved cage shunts construction. In this dissertation the analytical model of CMI’s cage shunts was established, based on calculating of trans-impedance from cascade matrix of passive two-port which is representing the shunt. Trans-impedance can be used for AC-DC difference and phase error calculation, which are two basic parameters of shunts. Uncertainty analysis of the model was done by means of Monte Carlo method. Next, this dissertation also concentrates on suitable measurement methods of phase error, AC-DC difference, and power a temperature coefficient of resistance. These measurements method were used for calibration of existing CMI’s cage shunts and so the model’s verification was made. Finally, theoretical optimization of existing CMI’s cage shunts constructions and theoretical designs of 20A, 50A and 100A shunts were done using sensitivity analysis results.
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