Wyniki 1-10 spośród 22 dla zapytania: authorDesc:"Grzegorz KOMARZYNIEC"

Damping of inrush current in superconducting transformer DOI:10.12915/pe.2014.12.56

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W pracy dokonano analizy zjawisk prądu włączania transformatorów z uzwojeniami wykonanymi z nadprzewodników wysokotemperaturowych. Przeanalizowano zjawisko tłumienia prądu włączania transformatora nadprzewodnikowego. Rezultaty analizy teoretycznej odniesiono do wyników otrzymanych z pomiarów jednofazowego transformatora HTS o mocy 8,5 kVA. Zwrócono uwagę na różnice występujące w przebiegu prądów włączania transformatorów nadprzewodnikowych i transformatorów konwencjonalnych. Wyjaśniono mechanizm tłumienia prądu transformatora HTS gdy jego uzwojenia znajdują się w stanie nadprzewodzenia i w stanie rezystywnym. Tłumienie prądu włączania transformatora nadprzewodnikowego. Abstract. In present study we analyze the inrush current in transformers with windings made of high-temperature superconducting materials. We analyze the phenomenon of damping the inrush current in superconducting transformers. Theoretical analysis results are compared with results of measurements of one-phase HTS 8,5 kVA transformer. We discuss differences in inrush current waveform in superconducting and conventional transformers. We also explain the damping mechanism of inrush current in HTS transformer when its windings are in superconductive, and in resistive states. S􀃡owa kluczowe: transformator, nadprzewodnictwo, transformator HTS, pr􀄅d w􀃡􀄅czania Keywords: transformer, superconductivity, HTS transformer, inrush current doi:10.12915/pe.2014.12.56 Introduction Transformers with windings made of superconductive materials are one of the most promising applications of high-temperature superconductors (HTS). The basic problem with exploitation of HTS transformers is keeping their windings in superconductive state. Loss of supercondu[...]

Increase in losses in a superconducting transformer due to inrush current DOI:10.15199/48.2015.04.09

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W pewnych okolicznościach, włączeniu nieobciążonego transformatora nadprzewodnikowego do sieci towarzyszyć może prąd włączania o dużej wartości. Na skutek nasycenia rdzenia, pole magnetyczne w kolumnie wielokrotnie przekracza wartość obliczeniową. W efekcie może mieć miejsce przekroczenie krytycznych wartości prądu oraz natężenia pola materiału nadprzewodnikowego, uzwojenia transformatora przechodzą ze stanu nadprzewodzenia do stanu rezystywnego. Wzrost strat przekłada się na wzrost temperatury nadprzewodnika, mogący prowadzić do termicznego uszkodzenia uzwojeń. W pracy poddano analizie wzrost strat w uzwojeniu transformatora HTS na skutek przepływu prądu włączania. Wzrost strat w transformatorze nadprzewodnikowym w skutek przepływu prądu włączania. Abstract. In some cases after the superconducting transformer is switched into the energetic network, core saturation occurs. Magnetic field is many times greater than the calculated field. The outer magnetic field causes increase in losses in superconducting transformer's windings. The effect is getting the windings from superconducting to resistive state. Increase in windings temperature in the resistive state can lead to irreversible superconductor degradation. Słowa kluczowe: prąd włączania, transformator, nadprzewodnik, straty. Keywords: inrush current, transfromers, superconductor, losses. Introduction The most useful feature of superconductors, with different practical applications in mind, is their ability to conduct great currents with minimal energetic losses. In a no load superconductive transformer (HTS) total losses are 50% and in full load 10% of losses a transformer with copper windings. The basic problem with exploitation of HTS transformers is maintaining their windings in superconductive state. Crossing any critical value of superconductor like critical temperature Tc, critical magnetic field rate Hc and critical current density Jc causes getting the superconductor[...]

Impact of critical current values in HTS transformer winding on decay time of inrush current DOI:10.15199/48.2016.02.47

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This paper presents mathematical analysis of the first inrush current pulse for transformers with windings made of superconducting materials. Formulas are derived hereby, allowing for calculation of pulse duration. Moreover, dependences are shown which allow for specifying the time when transformer’s primary winding is in the resistive state. Streszczenie. W artykule przedstawiono analizę matematyczną pierwszego impulsu prądu włączania transformatora z uzwojeniami wykonanymi z materiału nadprzewodnikowego. Wyprowadzono wzory umożliwiające wyliczenie czasu trwania impulsu. Podano również zależności umożliwiające określenie czasu przez jaki uzwojenie pierwotne transformatora znajduje się w stanie rezystywnym. (Wpływ wartości prądu krytycznego uzwojenia transformatora HTS na czas zaniku prądu włączania) Keywords: inrush current, transformers, superconductor. Słowa kluczowe: prąd włączania, transformator, nadprzewodnik. Introduction Transformers with windings made of superconducting materials are one of the most promising applications of high-temperature superconductors. The main process- and operations-related problem pertains to the method for maintaining their windings in the superconducting state. The inrush current phenomenon has been identified as an important issue here. On attempt to activate a superconducting transformer, due to the fact that the inrush current exceeds the value of superconductor’s critical current Ic, transition of windings from the superconducting to the resistive state takes place. This transition is accompanied by thermal effects in windings, related to the inrush current by means of the Joule’s law. They can lead to a thermal damage of the superconducting winding. The source of the transformer’s inrush current is a transient state in the electrical circuit coupled with the magnetic circuit [1]. Under certain conditions this state can result in transformer’s core saturation [...]

Determination of the amount of heat generated by the inrush current in the windings of a superconducting transformer DOI:10.15199/48.2016.03.18

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W pracy dokonano analizy ilości ciepła jaka wydziela się przy przepływie prądu włączania przez uzwojenie pierwotne transformatora nadprzewodnikowego. Wyprowadzono wzór na prąd włączania w stanie rezystywnym uzwojenia oraz na podstawie prawa Joule'a wyprowadzono wzór na ilość ciepła wydzielanego w uzwojeniu pierwotnym transformatora. Na tej podstawie wyznaczono charakterystyki zmienność ilości ciepła dla wybranych parametrów pracy transformatora. (Wyznaczanie ilości ciepła wydzielanego przez prąd włączania w uzwojeniach transformatora nadprzewodnikowego) Abstract. The text presents an analysis of the amounts of heat generated by the inrush current flowing through the primary winding of a superconducting transformer. A formula to describe the inrush current for the winding in the resistive state is derived. Then, a formula to describe the amount of heat generated in the primary winding of the transformer is derived on the basis of Joule's first law. This formed a basis for determining the characteristics of heat amount variability for selected transformer operation parameters. Słowa kluczowe: prąd włączania, transformator, nadprzewodnictwo, ciepło. Keywords: inrush current, transformer, superconductivity, heat. Introduction Transformers with windings made of superconducting materials constitute one of the most promising applications of high-temperature superconductors (HTS). In the case of a failure, replacement or repair of these devices is extremely expensive, due to high prices of superconducting materials. Therefore, a lot of care is taken to ensure protection of superconducting transformers, aimed at minimizing the risk of failure events. The basic problem - both technological and related to device service - consists in maintaining the windings of superconducting transformers in the superconducting state. The superconducting state will get destroyed if current of excessive density - referred to as the critical current density Jc[...]

Determination of the amount of heat generated by the inrush current in the windings of a superconducting transformer DOI:10.15199/48.2016.03.18

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W pracy dokonano analizy ilości ciepła jaka wydziela się przy przepływie prądu włączania przez uzwojenie pierwotne transformatora nadprzewodnikowego. Wyprowadzono wzór na prąd włączania w stanie rezystywnym uzwojenia oraz na podstawie prawa Joule'a wyprowadzono wzór na ilość ciepła wydzielanego w uzwojeniu pierwotnym transformatora. Na tej podstawie wyznaczono charakterystyki zmienność ilości ciepła dla wybranych parametrów pracy transformatora. (Wyznaczanie ilości ciepła wydzielanego przez prąd włączania w uzwojeniach transformatora nadprzewodnikowego) Abstract. The text presents an analysis of the amounts of heat generated by the inrush current flowing through the primary winding of a superconducting transformer. A formula to describe the inrush current for the winding in the resistive state is derived. Then, a formula to describe the amount of heat generated in the primary winding of the transformer is derived on the basis of Joule's first law. This formed a basis for determining the characteristics of heat amount variability for selected transformer operation parameters. Słowa kluczowe: prąd włączania, transformator, nadprzewodnictwo, ciepło. Keywords: inrush current, transformer, superconductivity, heat. Introduction Transformers with windings made of superconducting materials constitute one of the most promising applications of high-temperature superconductors (HTS). In the case of a failure, replacement or repair of these devices is extremely expensive, due to high prices of superconducting materials. Therefore, a lot of care is taken to ensure protection of superconducting transformers, aimed at minimizing the risk of failure events. The basic problem - both technological and related to device service - consists in maintaining the windings of superconducting transformers in the superconducting state. The superconducting state will get destroyed if current of excessive density - referred to as the critical current density Jc[...]

Temperature increase of the primary winding of a 14 kVA HTS transformer during the flow of the switching current DOI:10.15199/48.2018.04.19

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Transformer windings can conduct high currents, not only when short-circuited or overloaded, but under certain circumstances even after switching on the transformer to the energy grid. When the no load transformer is switched on, inrush current can reach 20÷40 times the rated current. The disappearing time of the inrush current wave can be up to several thousand periods of the supply voltage. The main exploitation problem of HTS transformers is the maintenance of the superconducting state of the windings. This is only possible when the point of operation of the superconducting wire P (Fig. 1) is below the critical area determined by absolute critical parameters [1]: critical temperature Tc, critical current Ic, critical magnetic field strength Hc. Exceeding the critical value of any of the parameters Tcp, Icp, Hcp causes instantaneous loss of superconductivity, as shown in Figure 2 [2]. Fig. 1. Critical area of the superconductor A switching current whose value is higher than the critical Icp for the high voltage winding of the transformer causes the loss of superconductivity in this winding. According to Joule's law, an increase in wire resistance results in an increase in its temperature, which may be higher than the critical Tcp. As a result of the temperature increase, the high voltage winding of the HTS transformer may lose its superconducting state for a long time. Longterm significant temperature rise can lead to thermal damage to the superconducting wire. Fig. 2. Simplified characteristics of superconductor transition HTS Transformer The tests were performed on a 13.8 kVA transformer (Fig. 3). An overview of the transformer’s structure is given in Fig. 4. Table 1 lists the rated characteristics of the transformer. Fig. 3. 14 kVA superconducting transformer The windings of the transformer were made from superconducting tape by SuperPower Inc. The high voltage winding used tape of the SCS4050-AP type, with a [...]

The influence of power supply network inductance on the HTS transformer inrush current DOI:10.15199/48.2018.12.55

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One of the problems associated with the operation of superconducting transformers (HTS) is the phenomenon of inrush currents occurring with sudden surges of voltage at the transformer terminals. The basic operational problem of HTS transformers is the necessity of uninterrupted maintenance of superconducting windings (HTS) at cryogenic temperature and preventing the loss of superconducting state in them. A high inrush current with a sufficiently long duration may cause the HTS windings to move to a resistive state. A state in which the HTS windings leave the superconductivity should be treated as an emergency condition of the HTS transformer's operation, hindering its switching on and creating a risk of possible interruption of winding continuity as a result of their thermal damage. The high density of currents in the second-generation high-temperature superconductor wires (HTS 2G) and the small area of heat exchange with the cooling medium make these conductors very susceptible to thermal damage [1] [2]. Inrush current The problems related to the occurrence of the inrush current of HTS transformers are: high amplitude of unidirectional current impulses, long decay time of the current wave and high content of higher harmonics [3]. The first impulse of the transformer inrush current may reach values 20÷40 times higher than the value of its rated current [4][5]. High prices of superconducting winding wires impose critical values of transformer winding currents being only slightly higher than their rated currents. As such, the occurrence of the HTS transformer inrush current leads to the loss of the superconducting state of its windings a large number of cases. The time of decay of the inrush current wave can range from several periods of supply voltage, for low power transformers, to several thousand periods for large units. It can be associated with long-term loss of the superconducting state of the transformer windings. [...]

Redukcja zakłóceń zapłonowych w reaktorach Gliding Arc

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W tekście omówiono system zapłonowy reaktora plazmowego GlidArc wykorzystujący elektrodę zapłonową. Zwrócono uwagę na jego wady i zaproponowano modyfikację sposobu realizacji zapłonu. Realizacja zapłonu z użyciem dwóch elektrod zapłonowych istotnie zmniejsza ilość zaburzeń przewodzonych do obwodów zasilania elektrod roboczych. Przedstawiono wady zaproponowanego rozwiązania i możliwości ich eliminacji. Abstract. The text discusses the GlidArc plasma reactor's ignition system that uses an ignition electrode. Attention was drawn to its defects and was proposed the modification of the ignition system. Implementation of the ignition with two electrodes significantly reduces the conducted disturbances to power circuitry of working electrodes. Disadvantages of the proposed solution are presented and possibilities of their elimination. (Noise ignition reduction in the Gliding Arc plasma reactor) Słowa kluczowe: reaktor plazmowy, układ zapłonowy, układ zasilania. Keywords: plasma reactor, ignition system, power system. Wstęp Podstawą prawidłowej pracy reaktorów Gliding Arc jest cykliczne występowanie wyładowań elektrycznych ślizgających się wzdłuż elektrod roboczych. Pojedynczy cykl pracy składa się z procesu zapłonu wyładowania, procesu rozwoju wyładowania i procesu gaszenia. By reaktor pracował cyklicznie z chwilą zgaszenia wyładowania (w tzw. strefie gaszenia) powinien natychmiast nastąpić zapłon wyładowania (w tzw. strefie zapłonu). W praktyce martwy czas może zawierać się od kilku mili sekund do kilku okresów napięcia zasilającego. Zależnie od parametrów zasilania w energię elektryczną (wartości napięcia, prądu i częstotliwości), parametrów panujących wewnątrz komory wyładowczej (temperatury, ciśnienia), składu chemicznego gazów procesowych. Zbyt długi czas martwy istotnie pogarsza warunki dla prowadzonych procesów plazmowych, dlatego jego wyeliminowanie jest pods[...]

13,8 kVA transformer with windings made of YBCO HTS tapes DOI:10.15199/48.2016.12.18

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W pracy przedstawiono konstrukcję jednofazowego transformatora z uzwojeniami wykonanymi z taśmy nadprzewodnikowej drugiej generacji. Wykreślono uzyskane z pomiarów charakterystyki stanu jałowego pracy i stanu zwarcia pomiarowego transformatora. Podano wartości impedancji zwarcia i jej składowych oraz starty mocy. We wnioskach końcowych podano uwagi do projektowania transformatorów nadprzewodnikowych oraz konkluzje wynikające z ich eksploatacji. (Transformator o mocy 13,8 kVA z uzwojeniami wykonanymi z taśmy nadprzewodnikowej YBCO). Abstract. This paper presents the design of one-phase transformer with the windings made of second generation of HTS tapes. The no-load operation and transformer short-circuit measurement characteristics were deleted from the measurements. The values of short-circuit impedance, its components and power losses were specified. In closing remarks comments were made on the designing of superconductor transformers and operational conclusions. Słowa kluczowe: transformator, nadprzewodnictwo, taśma nadprzewodnikowa. Keywords: transformer, superconductivity, HTS tapes. Introduction The first attempts to design superconductor transformers were taken in 1960s, when superconductors, at that time still low temperature, became easily available. High prices of superconductors and necessity to cool them down to temperature of 4.2K led to economic and technical problems. These problems were limited by the discovery of high temperature conductivity in 1986. At present the superconducting transformers are one of the most promising applications of superconductors [1] [2]. The most useful property of superconductors, from the perspective of their use in transformer windings, is the ability to conduct high currents at very low power losses [3]. The replacement of the conventional transformers in the power grid with superconducting transformers allows to reduce transmission losses by more than 60%. Small sections of HTS tap[...]

The influence of the geometry and resistance of the high voltage winding of the HTS transformer on the inrush current parameters DOI:10.15199/48.2018.01.14

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The inrush current of conventional transformers is a relatively well-known phenomenon. As regards superconducting transformers, there is comparatively little information on this subject. It is known that the inrush current of the superconducting transformers achieves higher values and longer decay times compared to the current of the conventional transformers. This is due to the different characteristics of superconducting windings, smaller dimensions of these windings and smaller magnetic cores of superconducting transformers. The study investigates the influence of the geometry and resistance of superconducting transformer windings on the values and decay time of inrush current on the basis of measurements of transformers of the power of 8.5 kVA and 13.8 kVA. Effect of winding geometry For the calculation of the maximum value of the first current pulse, the formula given by Specht [1] [2] is used: (1)           m m r n a m M B B B B L I E 2  where La is the inductance of the ring coil without iron, given by the relation: (2) l L z A a 0  2 in which A is the cross-section area of the high voltage winding (HV) (Fig. 1): (3) 4 D2 A   where D is the average diameter of the coil of the high voltage winding. The symbol l, occurring in formula (2), is the average length of the magnetic field lines that penetrate the coil. Other designations in the formulas: Em  maximum voltage of the source,   pulsation,   phase angle of the voltage, A  cross-section area of the winding, z  the number of coils, Bm  the maximum induction in the normal operation of the transformer, Br  induction of residual magnetism, Bn  induction of core saturation. From formula (1) it follows that with [...]

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