Расчет трансформатора -Transformer power calculation

 In this article I will try to tell you how to calculate a transformer for a welding machine.

EMC Aspects of PWM Controlled Loads in Vehicles Sabine Marksell-Department of Industrial Electrical Engineering and Automation Lund University-Licentiate Thesis

EMC Aspects of PWM Controlled Loads in Vehicles Sabine Marksell-Department of Industrial Electrical Engineering and Automation Lund University-Licentiate Thesis

Abstract The number of electrically driven loads in a modern vehicle is constantly increasing. Many loads that former were mechanically driven will in the future be driven by electricity. This implies that a number of electronic systems have to be packed together in the limited space in a vehicle. When different electronic systems are placed close to each other, there is always a risk for electromagnetic interference between the different systems causing malfunction or even failure. It is important to ensure that this does not happen, and this concept is called electromagnetic compatibility, EMC. EMC implies that different electrical systems should be able to work in close proximity without affecting each other. From the EMC point of view, integration of electric traction drives in present vehicles represents a considerable challenge. In order to save energy, many electrical loads can be controlled on demand. A common and energy efficient way to do this is to use a method called pulse width modulation, PWM, where the load voltage is pulsed in order to create the desired average output voltage. When this method is employed, the voltage pulses are present on the conductors between the power electronic converter and the load. Since the space in a vehicle is limited, it is often not possible to place the power electronic converter close to the load. Consequently, long conductors are often required between the power electronic converter and the load. The steep edges of the voltage pulses and the fundamental of the square wave, called the switching frequency, together with the long conductors cause electromagnetic interference problems. These disturbances could interfere with, for example, the radio in the vehicle. In this thesis, different electromagnetic compatibility aspects of a pulse width modulated system are investigated. Some solutions are proposed in order to mitigate the disturbances. The solutions involve increasing the rise and fall times of the voltage pulses and employing a randomly varying switching frequency. Also the effects from different conductor layouts, such as using the vehicle body sheet metal as a current return path or having the lead-in and return conductor close to each other, are investigated. In order to evaluate the results from the different setups, the voltage across the load and the radiated magnetic field are measured. The experimental results in this thesis show that a conductor should be used for current return and that this conductor should be placed as close to the lead-in conductor as possible in order to suppress electromagnetic noise. It is also shown that a randomly varying switching frequency will give a more broadband noise in the switching frequency range. Increasing the resistance of the gate resistor mitigates the disturbance in the higher frequency areas at the expense of increased switching losses.

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https://www.iea.lth.se/publications/Theses/LTH-IEA-1041.pdf

Electromagnetic compatibility of voltage source inverters for uninterruptible power supply system depending on the pulse-width modulation scheme-Krzysztof Bernacki, Zbigniew Rymarski ✉ Institute of Electronics, Faculty of Automatic Control and Computer Science of the Silesian University of Technology, Akademicka 16, 44-100 Gliwice, Poland

 IET Power Electronics Research Article Electromagnetic compatibility of voltage source inverters for uninterruptible power supply system depending on the pulse-width modulation scheme ISSN 1755-4535 Received on 22nd August 2014 Accepted on 6th January 2015 doi: 10.1049/iet-pel.2014.0637 www.ietdl.org Krzysztof Bernacki, Zbigniew Rymarski ✉ Institute of Electronics, Faculty of Automatic Control and Computer Science of the Silesian University of Technology, Akademicka 16, 44-100 Gliwice, Poland ✉ E-mail: zbigniew.rymarski@polsl.pl 

Abstract: The pulse-width modulation (PWM) scheme is an algorithm for inverter switch control. A two-leg bridge and three-level PWM are typical solutions in voltage source inverters in uninterruptible power supply systems. The three PWM schemes that are used in inverters are compared herein. Each scheme has different features, including the level of noise generated and interference in the different frequency ranges. The aim of this study is to analyse the characteristics and electromagnetic interference that is generated by an inverter using different PWM schemes. 

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https://ietresearch.onlinelibrary.wiley.com/doi/epdf/10.1049/iet-pel.2014.0637

Design and Implementation of Hybrid Active Power Filter (Hapf) for UPS System Mahendar Kumar1*, Zubair .A Memon1, M .Aslam Uqaili1-1Institute of Information & Communication Technologies (IICT) Mehran University of Engineering & Technology (MUET), Jamshoro Sindh, 76090, PAKISTAN

Design and Implementation of Hybrid Active Power Filter (Hapf) for UPS System Mahendar Kumar*, Zubair .A Memon, M .Aslam Uqaili 

Abstract: 

Hybrid Active Power Filter (HAPF) is designed and applied for Uninterrupted Power Supply (UPS) System to mitigate harmonic currents in UPS during the power conversion from rectifiers to inverters (AC-DC-AC Converters). Various UPS types and topologies are used for continuous power supply without delay and protection to connected loads. In spite of the fact that UPS is one of the power quality apparatus but it has also drawback of disturbing the power system quality of system by current harmonics and voltage distortion during conversion of power. Passive and EMI Filters could not eliminate harmonics effectively from UPS system therefore it requires modern, rapid filtering method as well combination of Active and Passive Filters. Proposed model of HAPF for UPS System could mitigate current harmonics for optimal power transfer and minimize losses, increase overall efficiency, reliability and life span of equipment. Higher harmonic current and higher voltage distortion leads to greater power loss. In this paper the (d-q) theorem is applied for the identification of harmonic currents. The d-q theorem and calculation creates the signal of reference compensation current and this produced signal of current is tracked by the yield current of the voltage source converter.. Hysteresis based controller for HAPF is applied to create the switching signals to regulate and maintain the voltage source converter output currents. Harmonics and efficiencies are analyzed at different loads and on charging and discharging of batteries of various UPS System in different industries and sectors on the basis of experimental investigation then HAPF is designed and implemented. In simulation results, it is observed that THD reduced from 46 to 10%, the harmonic currents were compensated and eliminated effectively which improved power quality of UPS System. Furthermore, addition of proposed HAPF could save the power up to 15 % which lost due to poor power quality of UPS System.

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https://publisher.uthm.edu.my/ojs/index.php/ijie/article/download/6727/3715/

Pulse Circuits by V.T. Frolkin; L.N. Popov

 

Pulse Circuits by V.T. Frolkin; L.N. Popov 

 This book explains the analysis and operation of all the most frequently used pulse circuits. It covers solid-state circuits, including their IC forms. The text contains a large number of problems and review questions that will help the reader to get better insight into the subject-matter. The authors start with pulse waveforms, move through RS-networks, to diode and transistor switching, logic gates, various forms of multivibrators, and flipflops as building blocks for the more complex networks. The material also covers sawtooth voltage and current generators, relaxation oscillators, and their applications.

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https://archive.org/details/v.-t.-frolkin-l.-n.-popov-pulse-circuits-mir-1982