Wyniki 1-5 spośród 5 dla zapytania: authorDesc:"Stanislav KOCMAN"

Filtration of harmonics in traction transformer substations, positive side effects on the additional harmonics

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The article deals with harmonics filtration in railway traction transformer substations. In traction transforms substations in the Czech Republic there are filters of 3rd and 5th harmonics. The article discuses side effect of these filters - suppression of additional harmonics. The article is based on measurement and simulation results. Streszczenie. Przedstawiono metodę filtracji harmonicznych w trakcyjnej podstacji transformatorowej. Przedfstawiono wyniki symulacji i pomiarów. (Filtracja harmonicznych w trakcyjnej podstacji transformatorowej). Keywords: traction, railway, harmonics, filtration Słowa kluczowe: trakcja, filtracja harmonicznych. Introduction With their rated power within tens of MW, electric railway substations are one of the biggest appliances in the electrical network. At the same time, they represent a potential source of huge interferences that can be transmitted into feeding network and irradiate into their surroundings. These interferences can also have negative impact on railway safety devices, which is unacceptable. These interfering influences include harmonic current distortion and, consequently, voltage distortion, as well as irradiation of a high frequency field [1] and high, fast current changes. In the case of AC electric railways, another effect is also unbalance, because it is one phase appliance in three-phase network. Of course, the electric railways have a number of advantages, and in the course of the 20th century, most of the important railways in Europe and elsewhere were electrified. As the importance of electric traction in the world is growing, it is also important to deal with the interferences that it brings. The authors of this article have studied this problem for many years, and they have also carried out a number of measurements on different traction substations. This article deals with harmonic distortion created by AC electric railways. Thanks to their high voltage (25kV) they [...]

Influence of Supply Voltage Quality on Harmonics Generated by AC Adjustable Speed Drives

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The paper presents results of computer simulations and experimental measurements for several topologies of AC adjustable speed drives fitted with selected devices for harmonics mitigation. Simulation models of the drive topologies have been developed using the program EMTP-ATP and tested under adjusted levels of supply voltage distortion. Both experimental measurements and simulations demonstrate high harmonic mitigation effectiveness of broad-band harmonic filter and active front end rectifier. Streszczenie. Artykuł prezentuje wyniki symulacji komputerowych oraz pomiarów doświadczalnych przeprowadzonych dla kilku układów napędowych prądu przemiennego o regulowanej prędkości, wyposażonych w wybrane urządzenia do łagodzenia wpływu harmonicznych. Modele symulacyjne badanych topologii układów napędowych zostały opracowane z wykorzystaniem oprogramowania EMTP-ATP i przetestowane w warunkach umożliwiających regulowanie stopnia odkształcenia napięcia zasilającego. Pomiary laboratoryjne jak również symulacje wykazały wysoką efektywność łagodzenia wpływu harmonicznych poprzez stosowanie szerokopasmowych filtrów harmonicznych oraz aktywnych prostowników. (Wpływ jakości napięcia zasilającego na wyższe harmoniczne generowane przez układu napędowe prądu przemiennego o regulowanej prędkości). Keywords: adjustable speed drives, current distortion, harmonics, voltage distortion. Słowa kluczowe: układy napędowe o regulowanej prędkości, odkształcenia prądu, harmoniczne, odkształcenia napięcia. Introduction Semiconductor converters in structures of such devices as adjustable speed drives, UPS or data processing and electronics devices used in various technical applications represent sources of harmonic currents generated into the power network to which they are connected [1-4]. Standard AC adjustable speed drives utilize the input three phase sixpulse diode rectifier for the AC-DC conversion, therefore the drawn current is n[...]

Efficiency determination of inverter-fed induction motor for low power applications

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The paper presents the measurement results of the efficiency of an induction motor, the new high efficiency class IE2 based on the direct efficiency measurement. For comparison purposes, the motor under test was fed by both a programmable three-phase AC power source and a frequency converter under the same conditions. The influence of the non-sinusoidal feeding and the harmonic power on the motor efficiency decreasing was investigated. T-model of the induction motor was used for computer simulations. Streszczenie. Artykuł prezentuje wyniki badań sprawnościowych silnika indukcyjnego klasy IE2 o wysokiej sprawności znamionowej, opartych na bezpośrednich pomiarach współczynnika sprawności. Dla celów porównawczych badany silnik zasilany był z trójfazowego, programowalnego źródła prądu przemiennego oraz przemiennika częstotliwości, w tych samych warunkach laboratoryjnych. Przeanalizowano wpływ zasilania niesinusoidalnego oraz wyższych harmonicznych na spadek sprawności badanego silnika. Podczas przeprowadzania symulacji komputerowych wykorzystano model T silnika indukcyjnego. (Badania sprawności silnika indukcyjnego zasilanego przekształtnikowo w układach małej mocy). Keywords: efficiency, induction motor, efficiency class, non-sinusoidal feeding. Słowa kluczowe: współczynnik sprawności, silnik indukcyjny, klasa sprawności, zasilanie niesinusoidalne. Introduction More and more public attention is now being focused on reducing energy consumption. New energy efficiency legislation has been drawn up in the EU in recent years to protect our environment [1] with an impact on the design of new induction motors as well. The EU has established mandatory minimum efficiency levels of induction motors for low power applications [2-4], which are going to come into force this year. The legislative changes have also caused modification of IEC standard methods for determining electrical machine efficiency [5] to be consistent with the majority of the wo[...]

Analyses of Behaviour of Induction Motor Supplied from Unbalanced Source

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The paper presents results of experimental measurements and computer simulations of an induction motor supplied from a programmable power source enabling an arbitrary adjusting of voltage quality on its output terminals. The tested motor was supplied under chosen levels of voltage unbalance to analyse some of its parameters. Motor simulation model has been also developed using the program EMTP-ATP to compare some its results to results obtained from experimental measurements. Streszczenie. W artykule zaprezentowano wyniki badań eksperymentalnych oraz rezultaty symulacji komputerowej silnika indukcyjnego zasilanego z programowanego źródła mocy umożliwiającego ustawianie dowolnej jakości napięcia. (Analiza właściwości silnika indukcyjnego zasilanego ze źródła o niezrównoważonych napięciach) Keywords: current unbalance, distortion, efficiency, induction motor, voltage unbalance Słowa kluczowe: silnik indukcyjny, nierównowaga napięć Introduction Three-phase squirrel cage induction motors are frequently used for both non-adjustable and adjustable electrical drives. Their large-scale using in various technical applications is given by their simple construction, reliability, low maintenance and relatively low cost. Induction motors implemented into non-adjustable speed drives not using frequency converters for their speed controlling draw current with a low level of distortion primarily depending on quality of the supply voltage, unlike the heavily distorted current drawn by the adjustable speed ones if no filtering technique is used. If the supply voltage is sinusoidal and balanced, the drawn motor current has only very low level of distortion. In this paper, the influence of voltage unbalance on motor current unbalance, motor current distortion, motor speed and motor efficiency is investigated for an induction motor supplied directly from a programmable power source. Voltage unbalance is one of the voltage characteristics of electric[...]

Simulation Models of Power Rectifiers in the EMTP-ATP Software DOI:10.12915/pe.2014.08.017

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The paper presents results of computer simulations of 6-pulse, 12-pulse and 18-pulse power rectifiers and their comparison to results from experimental measurements. To analyze their behaviour under various voltage quality conditions, simulation models have been developed using program EMTP-ATP. Performed simulations and measurements demonstrate a high effectiveness of the harmonic elimination of multi-pulse rectifiers. Nevertheless, it is affected by the quality of the supply voltage at the point of rectifier coupling as it is shown in the paper. Streszczenie. Zaprezentowano rezultaty komputerowej symulacji 6-, 12- i 18-pulsowego prostownika mocy oraz przedstawiono porównanie wyników symulacji z eksperymentem. Do symulacji yżto program EMTP-ATP. Symulacja prostownika mocy z wykorzystaniem programu EMTPATP Keywords: EMTP-ATP, harmonics, power rectifier, simulation. Słowa kluczowe: prostownik mocy, EMTP-ATP, symulacja. doi:10.12915/pe.2014.08.17 Introduction Power semiconductor converters are widely used in structures of variable speed drives to control their speed and torque. The most common type of these drives is AC drive with induction motor fed by frequency converter. The converter utilizes an input rectifier, most often as three phase 6-pulse diode. Rectifiers produce harmonic currents, which are generated into the power network with a negative impact on it and connected devices. In this case the current drawn by the drive is non-sinusoidal with a high level of distortion [1-4]. To determine its spectrum, harmonic analysis is applied. It enables to resolve a periodic nonsinusoidal function into a sum of sinusoidal waves - the Fourier series of the function: (1) [...]

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