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Tytuł:
The modeling of centrifugal pump transients
Autorzy:
Szymczyk, J.
Karaśkiewicz, K.
Powiązania:
https://bibliotekanauki.pl/articles/175255.pdf
Data publikacji:
2015
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
rotodynamic pumps
complete pump characteristics
transients
Opis:
Centrifugal pumps are part of larger hydraulic systems. These hydraulic machines can work not only in the pumping mode but in a number of other modes whose job description is possible using complete characteristics. Some of these modes, such as the turbine mode and the reversed turbine mode, may have practical significance. Knowledge of the transition from one steady state to another state allows to estimate instantaneous values such as, e.g., flow current and torque, which may be even a few times higher than nominal. The principal issues in these transients are amplitudes of parameters of these pumps and the time constants associated with the characteristics of the system.
Źródło:
Transactions of the Institute of Fluid-Flow Machinery; 2015, 130; 83-92
0079-3205
Pojawia się w:
Transactions of the Institute of Fluid-Flow Machinery
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Improved method for simulating transients of turbulent pipe flow
Autorzy:
Zarzycki, Z.
Kudźma, S.
Urbanowicz, K.
Powiązania:
https://bibliotekanauki.pl/articles/280935.pdf
Data publikacji:
2011
Wydawca:
Polskie Towarzystwo Mechaniki Teoretycznej i Stosowanej
Tematy:
unsteady pipe flow
transients
waterhammer
efficient numerical simulation
Opis:
The paper presents the problem of modelling and simulation of transients during turbulent fluid flow in hydraulic pipes. The instantaneous wall shear stress on a pipe wall is presented in the form of integral convolution of a weighting function and local acceleration of the liquid. This weighting function depends on the dimensionless time and Reynolds number. Its original, very complicated mathematical structure is approximated to a simpler form which is useful for practical engineering calculations. The paper presents an efficient way to solve the integral convolution based on the method given by Trikha (1975) for laminar flow. An application of an improved method with the use of the Method of Characteristic for the case of unsteady flow (water hammer) is presented. This method is characterised by high efficiency compared to traditional numerical schemes.
Artykuł przedstawia zagadnienie modelowania i symulacji przebiegów przejściowych podczas turbulentnego przepływu cieczy w przewodach ciśnieniowych. Chwilowe naprężenie styczne na ściance przewodu przedstawiono w postaci całki splotowej z funkcji wagi i przyspieszenia cieczy. Funkcja wagi dla naprężenia stycznego na ściance przewodu zależy od czasu bezwymiarowego i liczby Reynoldsa. Ma ona zawiłą postać matematyczną, dlatego aproksymowano ją do prostszej postaci, przydatnej do praktycznych obliczeń inżynierskich. Przedstawiono efektywny sposób rozwiązania całki splotowej, opierając się na metodzie podanej przez Trikha (1975) dla przepływu laminarnego. Podano zastosowanie ulepszonej metody symulacji naprężenia stycznego do metody charakterystyk podczas uderzenia hydraulicznego. Charakteryzuje się ona dużą efektywnością w stosunku do metody tradycyjnej.
Źródło:
Journal of Theoretical and Applied Mechanics; 2011, 49, 1; 135-158
1429-2955
Pojawia się w:
Journal of Theoretical and Applied Mechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Comparison of transformer modeling on riser pole arresters behavior during switching transients
Autorzy:
Abbaszadeh, A.
Abedi, M.
Doustmohammadi, A.
Powiązania:
https://bibliotekanauki.pl/articles/140474.pdf
Data publikacji:
2017
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
arresters
ATP software
ferroresonance
transformer
power system transients
Opis:
Arresters are widely used in power systems to protect other equipment against overvoltages. However, in some conditions, they can’t operate successfully. One of the disturbances leading to the failure of the riser pole arresters is the ferroresonance overvoltages. In this paper, at first the influence of different transformer simulation models of ATP software on the occurrence of ferroresonance is studied and then the effect of ferroresonance on the riser pole arrester has been scrutinized through the thermal and electrical performance of the arrester in an underground distribution system. The results show that the arrester temperature rises due to energy dissipation in a ferroresonance circumstance, which indeed may result into the explosion of the arrester. Also, applying different models of the transformer in the ATP software and comparing the results, it is shown that the available models do not show the same effect on the arrester.
Źródło:
Archives of Electrical Engineering; 2017, 66, 4; 717-730
1427-4221
2300-2506
Pojawia się w:
Archives of Electrical Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Modeling transients in MV resonantly grounded industrial grid during single line to ground faults
Autorzy:
Warecki, Jurij
Gajdzica, Michał
Powiązania:
https://bibliotekanauki.pl/articles/377060.pdf
Data publikacji:
2019
Wydawca:
Politechnika Poznańska. Wydawnictwo Politechniki Poznańskiej
Tematy:
electrical grid
grounding methods
transients overvoltage
transient intermittent faults
Opis:
Medium voltage distribution power grids mostly operate with ungrounded neutral points of transformer. The philosophy about these power supply systems based on the assumption that the electrical grid is more reliable. However the practice of operation showed that currents of single phase or multiple faults to ground depend mostly on the earth capacitances of cables connected to power grid and configuration and structure in relation to the main substation buses. Moreover, this kind of arcing ground faults on the ungrounded system causes transient overvoltages several times than nominal value. In the consequence, it may be dangerous for the electrical devices connected to the power system. The article focuses on the transient impact the equipment insulation due to faults in the middle voltage industrial grid with adjustable speed drives. The examination results of transient voltages across the system was presented. The Matlab/ Simulink Software was used to modeling system behavior during intermittent faults.
Źródło:
Poznan University of Technology Academic Journals. Electrical Engineering; 2019, 98; 65-75
1897-0737
Pojawia się w:
Poznan University of Technology Academic Journals. Electrical Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Effect of Hydraulic Characteristics on Fluid Transients Analysis under Different Types of Control Valves
Autorzy:
Al-Zaidi, Basim M.
Ismaeel, Abaas J.
Powiązania:
https://bibliotekanauki.pl/articles/2202314.pdf
Data publikacji:
2022
Wydawca:
Polskie Towarzystwo Inżynierii Ekologicznej
Tematy:
hydraulic characteristics
fluid transients
valve
Opis:
In this study, several types of valves were used to study the impact of the valves types and closure characteristics on fluid transients. The valve closure curves, which are the variation of the effective valve opening as a function of percentage opening area, were derived for different selected valves. Six different types of valves were selected to study the effect of the valves types on fluid transient conditions. For simplification, a very simple pipeline system was assumed and presented in this study. The system is about two pipes connected in a series junction and they take the water from a constant-level reservoir at upstream and a valve at downstream. The duration of valve closure was taken as six seconds which plays an important role in the pressure development in the system. A method of characteristics is applied to compute the transient conditions under gradual closure of the valves. Valve data of various forms were compiled and reported as discharge and headloss coefficients as a function of valve opening. The effect of valve geometry and operation on the relative valve opening were compared. Discharge and headloss coefficients were also compared between valve types. The study concluded that transient conditions depend on the valve type. The comparison between the results of all valve types indicated that the changes in pressure and discharges depend on valve type where there is a difference in effective valve opening. It can be concluded that the valve with the highest value of valve effective opening has less effect on transient conditions, i.e., the faster changes of effective valve opening the larger the effect on transient conditions (discharge and the greater the magnitude of the pressure wave). This study would help to select the property valve in pipeline design.
Źródło:
Journal of Ecological Engineering; 2022, 23, 12; 111--123
2299-8993
Pojawia się w:
Journal of Ecological Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Hydraulic transients analysis in pipe networks by the method of characteristics (MOC)
Autorzy:
Wichowski, R.
Powiązania:
https://bibliotekanauki.pl/articles/240954.pdf
Data publikacji:
2006
Wydawca:
Polska Akademia Nauk. Instytut Budownictwa Wodnego PAN
Tematy:
hydraulic transients
method of characteristics
single pipe
experimental measurement
pipe networks
numerical simulations
Opis:
The paper presents results of an experimental and theoretical study of the hydraulic transients in straight pipes and numerical simulations of unsteady flow in pipe networks. A mathematical model consists of a set of partial differential equations of hyperbolic type, which have been transformed by the method of characteristics into ordinary differential equations which are solved by the predictor-corrector method. Experimental tests have been performed, in order to examine the hydraulic transients phenomenon, in a single straight steel pipe. The experiments were carried out in the hydraulic laboratory of the Institute of Water Supply and Water Engineering, Environmental Engineering Faculty, Warsaw University of Technology. The numerical results show that the presented one dimensional model for a single pipe correctly describes the phenomenon since there is a good agreement with experimental maximum and minimum oscillations. In the paper, selected exemplary equations in a difference form for the pipe networks are also presented. One calculation example is given relating to the complex water-pipe network consisting of 17 loops, 48 pipelines and 33 nodes, supplied by two independent sources. Water-hammer throughout the whole pipeline network was caused by closing the gate valve at mid-point of one selected pipe. The results of the numerical calculations are presented in graphic form with respect to the final cross-sections of pipes.
Źródło:
Archives of Hydro-Engineering and Environmental Mechanics; 2006, 53, 3; 267-291
1231-3726
Pojawia się w:
Archives of Hydro-Engineering and Environmental Mechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Transients under energizing multiple power filter circuits
Autorzy:
Warecki, J.
Gajdzica, M.
Powiązania:
https://bibliotekanauki.pl/articles/97327.pdf
Data publikacji:
2016
Wydawca:
Politechnika Poznańska. Wydawnictwo Politechniki Poznańskiej
Tematy:
capacitor
reactor
harmonic filter
C–type filter
Static Var Compensator
transient overcurrent
transient overvoltage
dynamic overcurrent
dynamic overvoltage
switching transients
Opis:
The practice of operating reactive power compensation systems involving passive multiple filter circuits (FC) configured by single–tuned filters has shown, that it’s energizing can cause damage of the filter components. Impact of feasible FC configurations, including FC with a C–type filter, on switching overvoltages and overcurrents under the harmonic filters energizing were analyzed. Influence of the filters tuning on transient behavior has been shown. The transient analysis has been carried out by simulating of the FC within Matlab/Simulink software.
Źródło:
Computer Applications in Electrical Engineering; 2016, 14; 89-100
1508-4248
Pojawia się w:
Computer Applications in Electrical Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Transients in Transformers with Non-Uniform Inductance and Capacitance Distributions
Autorzy:
Saied, M. M.
Powiązania:
https://bibliotekanauki.pl/articles/262695.pdf
Data publikacji:
2017
Wydawca:
Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie
Tematy:
distributed parameter circuits
electromagnetic transients
integro-differential equations
modeling
mutual parameters
non-uniform
power transformers
transient response
winding
Opis:
The electromagnetic transients in transformer windings exhibiting location–dependent inductances and capacitances are investigated in the time domain. Analytical functions describing this dependence are assumed and incorporated in the two integro–differential equations governing the transient voltage and current distributions. The boundary conditions are available from the source initiating the transients and the winding’s end termination. A numerical procedure is applied in order to get frequency domain solutions for the voltage and current in the form of Interpolating and Parametric Functions. The numerical Laplace inversion is then applied to these s–domain expressions. Results pertinent to transients initiated by step- and double-exponential impulse sources are presented and discussed. All possible transformers’ neutral connections are considered. The possible error introduced by neglecting either or both of the inductance and capacitance non-uniformities is addressed. Results indicate that the main error is attributed to neglecting the inductance non-uniformity, whereas the impact of the capacitance non-uniformity is relatively small. In most cases, the winding’s copper and insulation losses have a small effect on the transient response.
Źródło:
Electrical Power Quality and Utilisation. Journal; 2017, 20, 1; 7-14
1896-4672
Pojawia się w:
Electrical Power Quality and Utilisation. Journal
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Numerical criterion for the duration of non-chaotic transients in ODEs
Autorzy:
Szczebiot, Ryszard
Kaczyński, Roman
Gołdyn, Leszek
Powiązania:
https://bibliotekanauki.pl/articles/2204683.pdf
Data publikacji:
2022
Wydawca:
Politechnika Białostocka. Oficyna Wydawnicza Politechniki Białostockiej
Tematy:
numerical criterion
non-chaotic transients
limit cycle
ODEs systems
Van der Pol oscillator
Opis:
The paper proposes an original numerical criterion for the duration analysis of non-chaotic transients based on the Euclidean norm of a properly defined vector. For this purpose, transient trajectories, prior to their entering a small neighbourhood of the limit cycle, are used. The vector has been defined with its components constituting the lengths of the sections, which connect the origin of the coordinate system with appropriately determined transient trajectory points. The norm of the vector for the analysis of non-chaotic transients has also been applied. As an assessment criterion of transients, the convergence of the norm to small neighbourhood of the limit cycle with the assumed accuracy is used. The paper also provides examples of the application of this criterion to the Van der Pol oscillators in the case of periodic oscillations.
Źródło:
Acta Mechanica et Automatica; 2022, 16, 4; 388--392
1898-4088
2300-5319
Pojawia się w:
Acta Mechanica et Automatica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A Study on the Low Frequency Transients in Power Transformers and Some Protection-Related Issues
Autorzy:
Saied, M. M.
Powiązania:
https://bibliotekanauki.pl/articles/1203944.pdf
Data publikacji:
2014
Wydawca:
Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie
Tematy:
transformer cores
inrush current
protection
transients
modeling
equivalent circuit
low frequency
nonlinear model
simulation
Opis:
This paper presents typical results for the non-linear low frequency transients following the energization of power transformers. The three operating conditions of no-load, full-load and internal faults are considered. A direct analytical procedure is applied for solving the corresponding set of differential equations describing the transformers equivalent circuit. The core representation is based on the use of curve fitting applied to their magnetization curves. The results include plots versus time for the supply current, the core flux, the magnetizing current as well as the internal induced voltage. Moreover, graphs for the hysteresis loops relating the instantaneous values of both the excitation current and the core flux are given. An approach is also presented for the numerical determination of the amplitudes of the different harmonics existing in any of these signals utilizing the corresponding equidistant samples. As examples, the DC offset as well as harmonics up to the fourth order are considered. It is shown that several useful features can be extracted from the results in both the time and harmonic domains that can assist in differentiating between overcurrents resulting from short-circuits or inrush phenomena.
Źródło:
Electrical Power Quality and Utilisation. Journal; 2014, 17, 2; 9-16
1896-4672
Pojawia się w:
Electrical Power Quality and Utilisation. Journal
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Analysis of Transients in a 4-Level Flying Capacitor Converter: Time Domain Approach. Part 2: Small Normalised Voltage Command
Autorzy:
Reznikov, Boris
Ruderman, Alex
Galanina, Valentina
Powiązania:
https://bibliotekanauki.pl/articles/1193863.pdf
Data publikacji:
2020
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
4-level DC–DC converter
flying capacitor
natural balancing
transients
Opis:
A 4-level flying capacitor converter (FCC) operation is considered on a base of discrete state-space model. A transition matrix is obtained for a pulse width modulation (PWM) period for small normalised voltage command values [0, 1/3]. The transition matrix elements are expanded into power series by small parameters. The matrix eigenvalues are presented in the form of power series as well. Six separate transients are constructed for six possible initial FCC states on a PWM period. Inductor current and capacitors’ voltage transients are found for the voltage source power-up as the arithmetic average of the six separate transients. Finally, the discrete solutions are replaced by equivalent continuous ones. Simple and accurate formulas for inductor current and capacitors’ voltage transients demonstrate good agreement with simulation results.
Źródło:
Power Electronics and Drives; 2020, 5, 40; 41-57
2451-0262
2543-4292
Pojawia się w:
Power Electronics and Drives
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Analysis of Transients in a 4-Level Flying Capacitor Converter: Time Domain Approach. Part 1: Large Normalised Voltage Command
Autorzy:
Reznikov, Boris
Ruderman, Alex
Galanina, Valentina
Powiązania:
https://bibliotekanauki.pl/articles/1193906.pdf
Data publikacji:
2020
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
4-level DC-DC converter
flying capacitor
natural balancing
transients
Opis:
A 4-level flying capacitor converter (FCC) operation is considered on a base of discrete state-space model. A transition matrix is obtained for a pulse width modulation (PWM) period for large normalised voltage command values [1/3, 1). The transition matrix elements are expanded into power series by small parameters. The matrix eigenvalues are presented in the form of power series as well. Six separate transients are constructed for six possible initial FCC states on a PWM period. Inductor current and capacitors’ voltage transients are found for the voltage source power-up as the arithmetic average of the six separate transients. Finally, the discrete solutions are replaced by equivalent continuous ones. Simple and accurate formulas for inductor current and capacitors’ voltage transients demonstrate good agreement with simulation results.
Źródło:
Power Electronics and Drives; 2020, 5, 40; 27-40
2451-0262
2543-4292
Pojawia się w:
Power Electronics and Drives
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Vibration transients of reservoir-pipe-valve system caused by water hammer
Autorzy:
Miao, Yang
Jiang, Yuncheng
Qiu, Zaihui
Pan, Jun
Wang, Lu
Han, Zhenrong
Li, Kun
Zhang, Li
Zhang, Xiaolu
Powiązania:
https://bibliotekanauki.pl/articles/1839616.pdf
Data publikacji:
2020
Wydawca:
Polskie Towarzystwo Mechaniki Teoretycznej i Stosowanej
Tematy:
reservoir-pipe-valve system (RPV system)
water hammer
vibration
transients
Opis:
A severe oscillation, accompanied with an abnormal “click” sound, of a fuel feeding pipe system during valve closing, when the feeding flowrate reaches a certain value, is observed experimentally. A fluctuation model in which stiffness and damping coefficients of the vibration system are time varying is proposed. Each coefficient is composed of two parts, one of which is constant and the other is time varying. Based on this model, simulation transients of the vibration displacement, velocity and pressure in the pipe are presented. Simulations of the pressure transients are compared with experimental data detected by pressure transducer, which shows that both have fluctuations in the transient process at a large flowrate.
Źródło:
Journal of Theoretical and Applied Mechanics; 2020, 58, 4; 1037-1048
1429-2955
Pojawia się w:
Journal of Theoretical and Applied Mechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Analysis of IGCT turn-on transients in circuit configurations with series connected diodes
Autorzy:
Tschirley, S.
Bernet, S.
Powiązania:
https://bibliotekanauki.pl/articles/262745.pdf
Data publikacji:
2006
Wydawca:
Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie
Opis:
This paper describes the effect of series connected diodes and their balancing networks m the clamp circuit in IGCT converters. It is shown, that the balancing of the clamp diodes has other requirements than the balancing of the series connected freewheeling diodes in the switch cell. The dynamic and static balancing of the clamp diodes is analyzed in detail.
Źródło:
Electrical Power Quality and Utilisation. Journal; 2006, 12, 2; 33-39
1896-4672
Pojawia się w:
Electrical Power Quality and Utilisation. Journal
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Double Injection Current Transients in a-Si:H
Autorzy:
Nekrašas, N.
Genevičius, K.
Juška, G.
Powiązania:
https://bibliotekanauki.pl/articles/1813197.pdf
Data publikacji:
2008-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
73.50.Gr
Opis:
In this work we present results of both computer modelling and experimental studies of double injection current transients in amorphous hydrogenated silicon thin layers.
Źródło:
Acta Physica Polonica A; 2008, 113, 3; 845-849
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Long lasting transients in power filter circuits
Autorzy:
Warecki, J.
Gajdzica, M.
Powiązania:
https://bibliotekanauki.pl/articles/97714.pdf
Data publikacji:
2014
Wydawca:
Politechnika Poznańska. Wydawnictwo Politechniki Poznańskiej
Tematy:
inrush current
arc fumace transformer
harmonic filter
switching transient
Opis:
The practice of operating AC electrical arc fumace power supply systems has shown that energizing unloaded fumace transformer can cause long lasting transients in filter circuits of static VAR compensators used in the supply systems. Examination of the supply system configuration impact on switching transient behaviour has been carried out by example of a 50 MVA arc fumace unit. The transient analysis has been carried out through simulating by Matlab/Simulink software.
Źródło:
Computer Applications in Electrical Engineering; 2014, 12; 324-333
1508-4248
Pojawia się w:
Computer Applications in Electrical Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Output characteristics of step-down (Buck) power converter
Autorzy:
Janke, W.
Bączek, M.
Walczak, M.
Powiązania:
https://bibliotekanauki.pl/articles/201669.pdf
Data publikacji:
2012
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
DC-DC converters
output characteristics
load transients
Opis:
The output characteristics of switched-mode dc-dc buck power converter are discussed. The shape of output characteristics is especially important for converters used for supplying modern processors. An output impedance is usually used for description of output characteristics. Many efforts are described in the literature to obtain the satisfastory features of closed-loop output impedance. Another approach, presented in the paper, is based on the concept of the output voltage response corresponding to the load conductance change, and is expressed by hr transmittance. Simulations of output characteristics of the buck converter in frequency and in time-domain have been performed for the ideal case as well as for a more realistic situation, with the parasitic resistances of converter elements included. The measurement results differ substantially from characteristics calculated for an ideal converter and are in good consistency with simulations including parasitics.
Źródło:
Bulletin of the Polish Academy of Sciences. Technical Sciences; 2012, 60, 4; 751-755
0239-7528
Pojawia się w:
Bulletin of the Polish Academy of Sciences. Technical Sciences
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Simulation of the magnetostrictive actuator transients
Autorzy:
Idziak, P.
Kowalski, K.
Nowak, L.
Barlak, M.
Pochrybniak, C.
Powiązania:
https://bibliotekanauki.pl/articles/377166.pdf
Data publikacji:
2015
Wydawca:
Politechnika Poznańska. Wydawnictwo Politechniki Poznańskiej
Tematy:
actuators
magnetostriction
electromagnetic field
transient analysis
Opis:
The paper deals with a magnetostrictive fast-acting actuator applied as a driving device for plasma valve. The actuator is characterized by a relatively small displacement (les then 0.1 mm), but with a very short response time – below 0.1 ms. System is designed for so called “high intensity plasma pulses gun” which is applied in the area of plasma physics and material engineering [1]. A structure with an axisymmetrical actuator energised by discharged pulses of a capacitor has been proposed. The field-circuit mathematical model of the dynamic operation of the actuator has been applied. The model includes: the equation of transient electromagnetic field in a non-linear ferromagnetic material and equation of electric circuit. Using the Borland Delphi 9.0 environment, the computer software has been elaborated. Results of simulation are presented.
Źródło:
Poznan University of Technology Academic Journals. Electrical Engineering; 2015, 83; 23-30
1897-0737
Pojawia się w:
Poznan University of Technology Academic Journals. Electrical Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Comparison of different methods for excitation of synchronous machines
Autorzy:
Schmuelling, S.
Kreischer, Ch.
Gołȩbiowski, M.
Powiązania:
https://bibliotekanauki.pl/articles/1367718.pdf
Data publikacji:
2015
Wydawca:
Sieć Badawcza Łukasiewicz - Instytut Napędów i Maszyn Elektrycznych Komel
Tematy:
AC machines
Brushless machines
Electromagnetic transients
Excitation system
Power system simulation
Opis:
The energy turnaround in Germany leads to new operating conditions for small and medium synchronous generators. Since the electricity generation through renewable energy sources, such as wind or photovoltaic, is highly volatile, generators have to run up from standstill into rated operation within several minutes. Hence, it is necessary to compensate a lack of electricity generation caused by wrong weather forecasts. Usually, gas turbine systems provide this possibility. The generator is used as a starter engine due to the connection to a frequency inverter. The excitation current is often provided by static excitation systems. Thus, it is possible to start from standstill and run up the drive until the gas turbine is able to generate a positive torque. A new excitation concept, based on an induction machine with a 3-phase rotor winding, is able to provide an excitation current at 0 rpm and eliminates the need for brushes. To verify the applicability for power systems, both systems are compared under different aspects. The control of the excitation current at different speeds and the possibility to settle shaft oscillations after electrical faults are aspects researched in the paper at hand. A power system simulation is performed with a synchronous machine connected to a grid. Both excitation systems are modeled by equivalent circuit diagrams in Matlab Simscape.
Źródło:
Maszyny Elektryczne: zeszyty problemowe; 2015, 3, 107; 89-93
0239-3646
2084-5618
Pojawia się w:
Maszyny Elektryczne: zeszyty problemowe
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Accidents of loss of flow for the ETTR-2 reactor: deterministic analysis
Autorzy:
El-Messiry, M.
Powiązania:
https://bibliotekanauki.pl/articles/146728.pdf
Data publikacji:
2000
Wydawca:
Instytut Chemii i Techniki Jądrowej
Tematy:
design base accidents
LOFA
loss of flow
pump coastdown
reactor transients
Opis:
The main objective for reactor safety is to keep the fuel in a thermally safe condition with adequate safety margins during all operational modes (normal-abnormal and accidental states). To achieve this purpose an accident analysis of different design base accident (DBA) as loss of flow accident (LOFA), is required for assessing reactor safety. The present work concerns this transients applied to Egypt Test and Research Reactor ETRR-2 (new reactor). An accident analysis code FLOWTR is developed to investigate the thermal behaviour of the core during such flow transients. The active core is simulated by two channels: 1 - hot channel (HC), and 2 - average channel (AC) representing the remainder of the core. Each channel is divided into four axial sections. The external loop, core plene, and core chimney are simulated by different dynamic lumps. The code includes modules for pump coast down, flow regimes, decay heat, temperature distributions, and feedback coefficients. FLOWTR is verified against results from RETRAN code, THERMIC code and commissioning tests for null transient case. The comparison shows a good agreement. The study indicates that for LOFA transients, provided the scram system is available, the core is shutdown safely by low flow signal (496.6 kg/s) at 1.4 s where the HC temperature reaches the maximum value of 45.64°C after shutdown. On the other hand, if the scram system is unavailable, and at t=47.33 s, the core flow decreases to 67.41 kg/s, the HC temperature increases to 164.02°C, and the HC clad surface heat flux exceeds its critical value of 400.00 W/cm2 resulting from the fuel burnout.
Źródło:
Nukleonika; 2000, 45, 4; 229-233
0029-5922
1508-5791
Pojawia się w:
Nukleonika
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Transients impact on power filter circuit sizing
Autorzy:
Warecki, J.
Gajdzica, M.
Powiązania:
https://bibliotekanauki.pl/articles/97523.pdf
Data publikacji:
2015
Wydawca:
Politechnika Poznańska. Wydawnictwo Politechniki Poznańskiej
Tematy:
capacitor
reactor
harmonic filter
transient and dynamic overvoltage
transient and dynamic overcurrent
equipment ratings
Opis:
The practice of operating multiple single-tuned filters in AC electrical arc furnace power supply systems has shown, that frequent energizing unloaded furnace transformer can cause damage of the filters. To examination of supply and filter system configuration impact on switching transient and dynamic overvoltages and overcurrents, an example of 50 MVA arc furnace unit was chosen. The transient analysis has been carried out by simulating within Matlab/Simulink Software. Using ANSI/IEEE Standards paper focuses on the selections of ratings for capacitors and air-core reactors used in multiple single-tuned harmonic filters configurations. Comparison of filter reactor and capacitor bank design based on steady state operation and transformer energizing was shown.
Źródło:
Computer Applications in Electrical Engineering; 2015, 13; 111-119
1508-4248
Pojawia się w:
Computer Applications in Electrical Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Parks Transformation Based Formulation For Power Systems Transients Detection
Autorzy:
Ferraz, R. G.
Iurinic, L. U.
Filomena, A. D.
Bretas, A. S.
Powiązania:
https://bibliotekanauki.pl/articles/410529.pdf
Data publikacji:
2013
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
Park's transformation
transient detection
power systems
Opis:
This paper presents proposed developments of a new formulation and a full algorithm for transient detection by applying Parks transformation. This approach consist in transforming three-phase voltage or current signals into Parks components known as direct, quadrature, and zero axes components. The input signals are local measurements of a power transmission or distribution system. Then, transients are superimposed in three-phase signals that can be detected in Parks components through the finite difference between samples. A full algorithm for the transient detection is presented and envisions the possibility of being applied in real time. In order to demonstrate the proposed algorithms performance, four case studies are considered: capacitor energizing, distribution transformer energizing, permanent resistive fault, and high impedance fault. These cases were simulated on a typical Brazilian sub-transmission line using Alternative Transient Program. As demonstrated by the case studies, the proposed formulation introduces further improvements for transient detection in power systems.
Źródło:
Present Problems of Power System Control; 2013, 4; 5-23
2084-2201
Pojawia się w:
Present Problems of Power System Control
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Obrazowanie termiczne stanów przejściowych przy załączaniu tyrystora
Thermal imaging of thyristor turn-on transients
Autorzy:
Kałuża, M.
Napiórkowski, K.
Powiązania:
https://bibliotekanauki.pl/articles/154464.pdf
Data publikacji:
2011
Wydawca:
Stowarzyszenie Inżynierów i Techników Mechaników Polskich
Tematy:
termowizja
przyrządy półprzewodnikowe mocy
thermovision
power semiconductor devices
Opis:
W artykule przedstawiono wyniki badań dotyczące możliwości zastosowania kamery termowizyjnej do rejestracji termogramów szybkich procesów przejściowych generacji ciepła w czasie załączania otwartej struktury półprzewodnikowej tyrystora. Badania wykazały możliwość rejestracji termogramów w czasie załączania przyrządu półprzewodnikowego mocy przy odpowiednim doborze niestandardowych ustawień pracy kamery termowizyjnej.
The paper presents the results of investigations on possible use of a thermal imaging camera for the recording of fast transient processes of heat generation during the switching of semiconductor structures in semiconductor power devices, based on measurements of a thyristor semiconductor structure. Using a measurement setup consisting of an IR camera and of a purpose build current pulse generator, the thermal behaviour of the T00-80 thyristor semiconductor structure during turn on was investigated. The thermograms were recorded at speeds reaching 1400 frames per second. Studies of the semiconductor structure of the thyristor mounted in a special holder showed the possibility of using a thermal camera for analyzing the behaviour of power semiconductor devices, however further increase in the temporal resolution of the recording process will be needed. One of the solutions will be to synchronize operation of a pulse generator and a thermal camera, including a controlled, variable time delay between current pulse generation and image acquisition.
Źródło:
Pomiary Automatyka Kontrola; 2011, R. 57, nr 10, 10; 1199-1201
0032-4140
Pojawia się w:
Pomiary Automatyka Kontrola
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Określanie charakterystyk drganiowych silników turbinowych w stanach nieustalonych
Determining vibration characteristics in marine turbine engines in transients conditions
Autorzy:
Grządziela, A.
Powiązania:
https://bibliotekanauki.pl/articles/223192.pdf
Data publikacji:
2011
Wydawca:
Akademia Marynarki Wojennej. Wydział Dowodzenia i Operacji Morskich
Tematy:
silnik turbinowy
charakterystyki
drgania
turbine engine
characteristics
vibrations
Opis:
W artykule przedstawiono metodę wyznaczania charakterystyk drganiowych okrętowych turbinowych silników spalinowych. Zaproponowano sposób akwizycji danych z pomiarów w stanach nieustalonych oraz metodykę badań procesów drganiowych zachodzących w procesach zimnego i gorącego rozruchu oraz wybiegu wirnika wytwornicy spalin.
The paper presents a method for determining vibration characteristics in marine turbine engines. It proposes a way of data acquisition from measurements in transient conditions, as well as methodology for investigating vibration processes occurring under run-up and shut-down engine processes and rotor coasting of gas generator.
Źródło:
Zeszyty Naukowe Akademii Marynarki Wojennej; 2011, R. 52 nr 3 (186), 3 (186); 57-64
0860-889X
Pojawia się w:
Zeszyty Naukowe Akademii Marynarki Wojennej
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
On the Interaction Between Theory, Experiments, and Simulation in Developing Practical Learning Control Algorithms
Autorzy:
Longman, R. W.
Powiązania:
https://bibliotekanauki.pl/articles/908249.pdf
Data publikacji:
2003
Wydawca:
Uniwersytet Zielonogórski. Oficyna Wydawnicza
Tematy:
automatyka
robotyka
iterative learning control
ILC
2D systems
learning transients
Opis:
Iterative learning control (ILC) develops controllers that iteratively adjust the command to a feedback control system in order to converge to zero tracking error following a specific desired trajectory. Unlike optimal control and other control methods, the iterations are made using the real world in place of a computer model. If desired, the learning process can be conducted both in the time domain during each iteration and in repetitions, making ILC a 2D system. Because ILC iterates with the real world, and aims for zero error, the field pushes the limits of theory, modeling, and simulation, to predict the behavior when applied in the real world. It is the thesis of this paper that in order to make significant progress in this field it is essential that the research effort employ a coordinated simultaneous synergistic effort involving theory, experiments, and serious simulations. Otherwise, one very easily expends effort on something that seems fundamental from the theoretical perspective, but in fact has very little relevance to the performance in real world applications.
Źródło:
International Journal of Applied Mathematics and Computer Science; 2003, 13, 1; 101-111
1641-876X
2083-8492
Pojawia się w:
International Journal of Applied Mathematics and Computer Science
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-25 z 70

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