Wyniki wyszukiwania - BazTech

1

Mathematical modeling of starting modes and static characteristics of a wound-rotor induction motor in phase coordinates

Malyar Vasyl, Hamola Orest, Maday Volodymyr, Vasylchyshyn Ivanna

Przegląd Elektrotechniczny

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2023

|

R. 99, nr 10

114--119

EN

The algorithms for calculating steady-state modes, static characteristics, and transients in an asynchronous drive based on a wound-rotor induction motor and a starter in a rotor circuit are presented. The calculation is based on a mathematical model of an induction motor that takes into account the saturation of the magnetic circuit. The electromagnetic processes are described by a nonlinear system of equations of electrical equilibrium composed in a fixed three-phase coordinate system, the coefficients of which are the differential inductances of the circuits. The steadystate modes and static characteristics are calculated by solving the boundary value problem using the continuation method in the parameter.

PL

Przedstawiono algorytmy obliczania trybów pracy w stanie ustalonym, charakterystyk statycznych i stanów nieustalonych w napędzie opartym na silniku indukcyjnym z wirnikiem fazowym i rozrusznikiem obwodu wirnikowego. Obliczenia oparte są na modelu matematycznym silnika indukcyjnego uwzględniającym nasycenie obwodu magnetycznego. Procesy elektromagnetyczne opisane są nieliniowym układem równań równowagi elektrycznej w ustalonym trójfazowym układzie współrzędnych, z indukcyjnościami różnicowymi obwodów jako współczynnikami. Tryby pracy w stanie ustalonym i charakterystyki statyczne oblicza się rozwiązując problem wartości granicznych metodą kontynuacji w parametrze.

2

Simulating transient flow in unsaturated porous media using finite-difference modeling

Chetti Ahmed

Geomatics, Landmanagement and Landscape

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2023

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no. 4

247--258

EN

The purpose of this study concerns the establishment of numerical model of transient flow in a variably saturated porous medium. Groundwater flow can only be studied adequately if one considers the fluxes between the saturated and the unsaturated zones through the free surface. However, this water table undergoes variations in level resulting either from losses of mass by gravity drainage or evaporation or from an excess of mass by infiltration from the surface of the porous medium. This describes the various phenomena that groundwater flow can undergo, such as gravity drainage, infiltration and evaporation. The adopted model is based on the Richards equation, which is a parabolic and strongly non-linear equation. The h-based form of the Richards equation is solved numerically by using the 1D upwind finite difference method. Referring to published experimental work and comparing our numerical results with their results, we have obtained a good fit. The importance of this model lies in its simplicity and its generality in treating the different flow states in a variably saturated porous medium, and therefore its usefulness in practice for a wide range of applications, contributing significantly to the understanding of transient flow phenomena in variably saturated porous media. Its capacity to address the complexities of groundwater movement, including gravity-driven drainage, infiltration, and evaporation, underlines its versatility and its potential to make meaningful contributions to various scientific and engineering fields.

3

Mathematical modeling of processes and characteristics of wound-rotor induction motor

Malyar Vasyl, Hamola Orest, Maday Volodymyr, Vasylchyshyn Ivanna

Przegląd Elektrotechniczny

|

2022

|

R. 98, nr 4

90--93

EN

A mathematical model and algorithm to calculating electromechanical transients and starting static characteristics of wound-rotor induction motor have been developed. The calculation is based on a mathematical model of an induction motor, which considers the saturation of the magnetic circuit and the differential method of calculating the static characteristics. The electromagnetic processes in the motor are described by a system of nonlinear electric equilibrium equations written in transformed to orthogonal coordinate axes, which are solved by the parameter continuation differential method and Newton's iterative method. Calculation of loop fluxes and differential inductances is performed using the magnetization characteristic of the main magnetic flux and the stator and rotor leakage fluxes.

PL

Opracowano model matematyczny i algorytm do obliczania przebiegów elektromechanicznych i rozruchowych charakterystyk statycznych silnika indukcyjnego z wirnikiem uzwojonym. Obliczenia opierają się na modelu matematycznym silnika indukcyjnego, który uwzględnia nasycenie obwodu magnetycznego oraz różnicową metodę obliczania charakterystyk statycznych. Procesy elektromagnetyczne w silniku opisane są układem nieliniowych równań równowagi elektrycznej, zapisanych w postaci przekształconej na osie ortogonalne, które są rozwiązywane metodą różniczkową z kontynuacją parametrów oraz metodą iteracyjną Newtona. Obliczanie strumieni pętli i indukcyjności różnicowych odbywa się na podstawie charakterystyki magnetyzacji głównego strumienia magnetycznego oraz strumieni rozproszenia stojana i wirnika.

4

Automatic identification of malfunctions of large turbomachinery during transient states with genetic algorithm optimization

Barszcz Tomasz, Zabaryłło Mateusz

Metrology and Measurement Systems

|

2022

|

Vol. 29, nr 1

175--190

EN

Turbines and generators operating in the power generation industry are a major source of electrical energy worldwide. These are critical machines and their malfunctions should be detected in advance in order to avoid catastrophic failures and unplanned shutdowns. A maintenance strategy which enables to detect malfunctions at early stages of their existence plays a crucial role in facilities using such types of machinery. The best source of data applied for assessment of the technical condition are the transient data measured during start-ups and coast-downs. Most of the proposed methods using signal decomposition are applied to small machines with a rolling element bearing in steady-state operation with a shaft considered as a rigid body. The machines examined in the authors’ research operate above their first critical rotational speed interval and thus their shafts are considered to be flexible and are equipped with a hydrodynamic sliding bearing. Such an arrangement introduces significant complexity to the analysis of the machine behavior, and consequently, analyzing such data requires a highly skilled human expert. The main novelty proposed in the paper is the decomposition of transient vibration data into components responsible for particular failure modes. The method is automated and can be used for identification of turbogenerator malfunctions. Each parameter of a particular decomposed function has its physical representation and can help the maintenance staff to operate the machine properly. The parameters can also be used by the managing personnel to plan overhauls more precisely. The method has been validated on real-life data originating from a 200 MW class turbine. The real-life field data, along with the data generated by means of the commercial software utilized in GE’s engineering department for this particular class of machines, was used as the reference data set for an unbalanced response during the transients in question.

5

Analysis of transient natural convective flow of a nanofluid in a vertical tube

Jha Basant K., Chitumu Ali J., Oni Michael O.

International Journal of Applied Mechanics and Engineering

|

2021

|

Vol. 26, no. 2

31--46

EN

An analysis into the transient natural convective flow of a nanofluid in a vertical tube is made. The governing equations of momentum, heat transfer and nanoparticle volume fraction are deduced, and the influence of the thermophoresis parameter and Brownian motion is incorporated. By direct integration and variation of the parameter, analytical solutions are obtained for flow formation and heat/mass transfer at steady-state. On the other hand, due to the complexity of same problem at transient state, a numerical solution is used to solve the discretized equations of motion using the implicit finite difference technique. The influence of the thermophoresis parameter and Brownian motion is noted and well discussed. For accuracy check, a numerical comparison is made between the steady state and transient state solution at large time; this comparison gives an excellent agreement. The role of various principal parameters on velocity profile, temperature, concentration of nanoparticles, Sherwood and Nusselt numbers are presented graphically and well discussed. It is noted that the buoyancy ratio decreases the fluid velocity significantly.

6

The transient analysis of the hydrogenerator of Nurek HPP subject to automatic excitation control action

Safaraliev Murodbek, Rasulzoda Khusrav Nazir, Otashbekov Rajabbek Ayombekovich, Rahimov Jamshed Bobomurodovich, Pavlyuchenko Dmitry Anatolievich

Przegląd Elektrotechniczny

|

2020

|

R. 96, nr 8

35--38

EN

At present time, the task of studying the operating conditions of synchronous generators operating in parallel with the power system taking into account the introduction of new capacities in the system and increasing their stability provokes interest for research. An effective mean of the stability of power plants, as part of the power system, is automatic excitation control. The simulation environment MATLAB / Simulink is widely used in the calculation and analysis of normal steady-state and transient conditions of electrical systems. The article presents the results of the study and the comparison of operating parameters on the example of the Nurek hydropower plant. The results obtained will be useful in studying the use of modern types of AEC in the excitation system of the generators of Nurek HPP.

PL

Skutecznym środkiem stabilności elektrowni, jako części systemu elektroenergetycznego, jest automatyczna kontrola wzbudzenia. Środowisko symulacyjne MATLAB / Simulink jest szeroko stosowane w obliczeniach i analizach normalnych stanów ustalonych i stanów nieustalonych układów elektrycznych. W artykule przedstawiono wyniki badań i porównanie parametrów eksploatacyjnych na przykładzie elektrowni wodnej Nurek. Uzyskane wyniki będą przydatne w badaniu wykorzystania nowoczesnych typów AEC w układzie wzbudzenia generatorów Nurek HPP.

7

Dobór wartości znamionowych filtrów przemysłowych

Varetsky Yuriy, Gajdzica Michał

Przegląd Elektrotechniczny

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2020

|

R. 96, nr 3

77--81

PL

Parametry znamionowe układów kompensacyjno-filtrujących wyznaczane są w oparciu o harmoniczne prądów i napięć w stanach ustalonych co tyczy się głównie jednostek filtrujących o prostej topologii. Jednak w przypadku bardziej złożonych układów wymaga się, aby elementy były dostosowane do pracy zarówno w warunkach ustalonych, jak i przejściowych. Korzystając ze standardów oraz norm, w artykule omówiono procedurę doboru parametrów baterii kondensatorów i dławików układów filtrujących z pozycji ich bezawaryjnej pracy w sieciach przemysłowych.

EN

The component ratings of single-tuned or single branch harmonic filter applications are often specified based solely on a combination of steady state fundamental and harmonic voltages and currents. Although for more complex harmonic filter circuits are required to be adapted to operate as well in steady state and transient conditions. Using the standards and norms, the article discusses the procedure for selecting the ratings of capacitor banks and reactors of the filtering systems from the point of view of their trouble-free operation in industrial grids.

8

Analysis and modelling of failure states in electric vehicle charging infrastructure

Stosur Mariusz, Kuniewski Maciej, Sowa Kacper, Blaszczyk Paweł, Uramek Andrzej

Przegląd Elektrotechniczny

|

2020

|

R. 96, nr 7

13--18

EN

This paper presents modeling methodology and simulation results of failure states and transients in electric vehicle (EV) charging infrastructure for investigation a potentially dangerous phenomenon that might appear during a typical operation. Transients can occur during normal work and during faults in EV Chargers. The trend in the electric cars suggests that in the future ultra-fast chargers would be the dominant one, therefore the focus is put-on high-power chargers (> 50 kW). During failure states of EV chargers’ transients occurred in network can impact on other chargers or can propagate along power lines and affect other electrical power equipment. Studies and simulations have been carried out using EMTP-ATP software package on the test model circuit especially prepared for this paper purpose.

PL

W pracy przedstawiono metodologię modelowania i wyniki symulacji stanów awaryjnych oraz stanów nieustalonych w infrastrukturze ładowania pojazdów elektrycznych (EV) w celu zbadania potencjalnie niebezpiecznego zjawiska, które może wystąpić podczas eksploatacji. Trend rozwoju pojazdów elektrycznych sugeruje, że w przyszłości będą dominowały ultraszybkie ładowarki, dlatego w artykule nacisk położony jest na analizę ładowarek dużej mocy (> 50 kW). Podczas awarii ładowarki stany przejściowe występujące w sieci, mogą oddziaływać na inne ładowarki lub mogą rozchodzić się wzdłuż linii zasilania i wpływać na inne urządzenia elektryczne. Badania i symulacje przeprowadzono przy użyciu pakietu oprogramowania EMTP-ATP w modelowym układzie stacji ładowarek.

9

Analysis of Transients in a Three-Level DC–DC Flying Capacitor Converter. Time Domain Approach

Reznikov Boris, Ruderman Alexander, Galanina Valentina

Power Electronics and Drives

|

2019

|

Vol. 4 (39)

33--45

EN

The paper considers a discrete state-space model for transients in a three-level flying capacitor DC–DC converter. A transition matrix is obtained for a pulse width modulation (PWM) period. The matrix elements are expanded into a power series using a selected small parameter. The matrix eigenvalues that determine the natural balancing dynamics transients are presented in the form of power series as well. Four separate transients are constructed based on four possible PWM period initial states (topologies). Inductor current and capacitor voltage transients are found for the voltage source power-up as the arithmetic average of the four separate transients. The discrete solutions are replaced by continuous ones. The resulting transients that are elementary functions of the circuit parameters, PWM period, and voltage reference demonstrate good agreement with the simulation results.

10

Hall effect on MHD transient flow past an impulsively started infinite horizontal porous plate in a rotating system

Prabhakar Reddy B.

International Journal of Applied Mechanics and Engineering

|

2018

|

Vol. 23, no. 2

471--483

EN

In this paper, the effect of Hall current on an unsteady MHD transient three dimensional flow of an electrically conducting viscous incompressible fluid past an impulsively started infinite horizontal porous plate relative to a rotating system has been studied. It is assumed that the entire system rotates with a constant angular velocity about the normal to the plate and a uniform magnetic field is applied along the normal to the plate and directed into the fluid region. The magnetic Reynolds number is assumed to be so small that the induced magnetic field can be neglected. The expressions for the primary and secondary fields and shearing stress at the plate due to primary and secondary velocity fields are obtained in a non-dimensional form. The non-dimensional governing equations of the flow are solved by using the Galerkin FEM. The effects of the physical parameters, such as the Hartmann number (M), rotation parameter (Ω), porosity parameter (K) and Hall parameter (m) on primary and secondary velocities and shearing stresses τx and τy due to primary and secondary velocities are discussed through graphs and tables, and results are physically interpreted.

11

On the accuracy of detailed model inductance matrix estimation for air core winding

Ahour J. N., Seyedtabaii S., Gharehpetian G. B.

Archives of Electrical Engineering

|

2017

|

Vol. 66, nr 4

787--799

EN

Researchers have used various methods to determine the parameters of transformer- equivalent circuits in transient studies. But most of these previous algorithms had difficulty finding the equivalent circuit parameters in a bigger model. This paper presents a new method to extract the inductance matrix of a detailed model for an air core winding for transient studies using frequency-response measurement data. This matrix can be determined with acceptable accuracy by using the proposed method. The biggest advantage of the proposed method is a reduction in the search space, and thus, speedier problemsolving. Simulations showed that the use of the proposed method leads to better behavioural quality of a transformer winding. The simulation results of the previous and proposed methods were compared with the help of a 20/0.4 kV, 1600 kVA transformer. This comparison showed the accuracy and superiority of the proposed method.

12

Computer aided analysis of transient states in linear circuits

Trojnar M.

Prace Naukowe Politechniki Śląskiej. Elektryka

|

2016

|

z. 1

19--29

EN

The article presents examples of application of chosen computer Programs in the analysis of transient states in linear circuits. Analytical solution of two Circuits (calculation of currents and voltage) has been presented on the basis of classical method and Laplace transform method. The circuits were then subjected to computer simulation in multisim and pspice programs. moreover, Mathcad program was used to solve one of the calculation examples. each of the computer programs mentioned can be successfully applied to analysis of transient states in electrical circuits, both for educational purposes and in scientific research.

PL

W artykule przedstawiono przykłady zastosowania wybranych programów komputerowych w analizie stanów nieustalonych w obwodach liniowych. w oparciu o metodę klasyczną oraz metodę operatorową zilustrowano analityczne rozwiązanie dwóch obwodów (obliczanie prądów i napięcia), które następnie poddano symulacji komputerowej w programach Multisim oraz pspice. Do rozwiązania jednego z przykładów obliczeniowych wykorzystano także program Mathcad. Każdy z wymienionych programów komputerowych z powodzeniem może znaleźć zastosowanie w analizach stanów nieustalonych w obwodach elektrycznych, zarówno w aspekcie dydaktycznym, jak i naukowym.

13

Optimization of start-up conditions to reduce thermal loads in cooled components of a supercritical steam turbine

Kosman W.

Journal of Power Technologies

|

2015

|

Vol. 95, spec.

47--53

EN

The paper describes the analysis of a start-up process of supercritical steam turbines. The problem under the investigation is the decrease of thermal loads due to the designs that are specific to this type of machines. The analysis focuses on the main components - the rotor and the inner casing that operate under the highest level of the thermal loads. The analysis involves the determination of the temperature and the stress fields and the behavior in the response to transient loading (thermal elongations). The obtained results allow to compare various cases of the transient loading.

14

Numerical study of the heat transfer phenomenon of a rectangular plate including void, notch using finite difference technique

Deb Nath S. K., Peyada N. K.

International Journal of Applied Mechanics and Engineering

|

2015

|

Vol. 20, no. 4

733--756

EN

In the present study, we have developed a code using Matlab software for solving a rectangular aluminum plate having void, notch, at different boundary conditions discretizing a two dimensional (2D) heat conduction equation by the finite difference technique. We have solved a 2D mixed boundary heat conduction problem analytically using Fourier integrals (Deb Nath et al., 2006; 2007; 2007; Deb Nath and Ahmed, 2008; Deb Nath, 2008; Deb Nath and Afsar, 2009; Deb Nath and Ahmed, 2009; 2009; Deb Nath et al., 2010; Deb Nath, 2013) and the same problem is also solved using the present code developed by the finite difference technique (Ahmed et al., 2005; Deb Nath, 2002; Deb Nath et al., 2008; Ahmed and Deb Nath, 2009; Deb Nath et al., 2011; Mohiuddin et al., 2012). To verify the soundness of the present heat conduction code results using the finite difference method, the distribution of temperature at some sections of a 2D heated plate obtained by the analytical method is compared with those of the plate obtained by the present finite difference method. Interpolation technique is used as an example when the boundary of the plate does not pass through the discretized grid points of the plate. Sometimes hot and cold fluids are passed through rectangular channels in industries and many types of technical equipment. The distribution of temperature of plates including notches, slots with different temperature boundary conditions are studied. Transient heat transfer in several pure metallic plates is also studied to find out the required time to reach equilibrium temperature. So, this study will help find design parameters of such structures.

15

Symulacja chaosu ferrorezonansowego za pomocą programu MicroTran

Łuszcz K, Sowa P.

Przegląd Elektrotechniczny

|

2014

|

R. 90, nr 8

116-121

PL

W artykule omówiono wyniki badań dotyczących powstawania zjawiska chaosu ferrorezonansowego w układzie elektroenergetycznym, przeprowadzonych za pomocą programu symulacyjnego MicroTran. Celem badań było rozeznanie możliwości modelowania układu dla celów chaosu ferrorezonansowego oraz rozpatrzenie warunków wystąpienia tego zjawiska w systemie elektroenergetycznym. Wnioski uzyskane z rezultatów takich badań stanowić jednak mogą podstawę do stworzenia procedur postępowania podczas planowania rozwoju systemu elektroenergetycznego, również w zakresie przyłączania nowych odbiorów do istniejących struktur zmieniających w istotny sposób warunki pracy badanego układu.

EN

This paper presents the results of investigations of the nonlinear dynamic ferroresonance phenomena in a power system, when taking into consideration the chaotic behavior. The basic tool for numerical investigations was the MicroTran program. The aim of the study was to explore the possibility of modeling system for the chaos ferroresonance and consideration of the occurrence of this phenomenon in the power system. Conclusions received from the results of investigation, can create the basis for the procedures for the planning of development the power system, even for the connection of new customers to existing structures.

16

Identyfikacja zakłóceń w wielotorowych różnopoziomowych napięciowo liniach elektroenergetycznych

Kumala R., Sowa P.

Przegląd Elektrotechniczny

|

2014

|

R. 90, nr 8

113-115

PL

W artykule omówione zostały skutki występowania zakłóceń zwarciowych niejednoczesnych w wielotorowych liniach przesyłowych. Analizę przeprowadzono na podstawie wyników obliczeń otrzymanych dla układu pracującego w warunkach rzeczywistych - wykorzystanego w analizie weryfikacyjnej.

EN

In the paper are discussed effects of complex shortcuts in multilines transmission lines. The analysis is performed on the basis of calculation of results obtained in real conditions.

17

One-dimensional uniform and time varying solute dispersion along transient groundwater flow in a semi-infinite aquifer

Singh M., Ahamad S., Singh V.

Acta Geophysica

|

2014

|

Vol. 62, no. 4

872--892

EN

An analytical solution for the space-time variation of contaminant concentration in one-dimensional transient groundwater flow in a homogenous semi-infinite aquifer, subjected to time-dependent source contamination, is derived. The uniform and time varying dispersion along transient groundwater flow is investigated under two conditions. First, the flow velocity distribution in the aquifer is considered as a sinusoidally varying function, and second, the flow velocity distribution is treated as an exponentially increasing function of time. It is assumed that initially the aquifer is not solute free, so the initial background concentration is considered as an exponentially decreasing function of the space variable which is tending to zero at infinity. It is assumed that dispersion is directly proportional to the square of the velocity, noting that experimental observations indicate that dispersion is directly proportional to the velocity with a power ranging from 1 to 2. The analytical solution is illustrated using an example and may help benchmark numerical codes and solutions.

18

Stany dynamiczne w rozruszniku samochodowym z magnesami neodymowymi

Ciurys M., Dudzikowski I.

Przegląd Elektrotechniczny

|

2013

|

R. 89, nr 9

10-14

PL

Opracowano rozrusznik samochodowy z magnesami neodymowymi i przekładnią planetarną. Za pomocą opracowanego algorytmu i programu obliczono przebiegi czasowe wielkości elektrycznych i mechanicznych w układzie: akumulator – rozrusznik samochodowy – silnik spalinowy. Zastosowano metodę obwodowo-polową. Wyznaczono przebiegi czasowe w analizowanym układzie w różnej temperaturze otoczenia. Porównano parametry opracowanego rozrusznika wzbudzanego magnesami neodymowymi z parametrami rozrusznika o magnesach ferrytowych.

EN

A car starter with neodymium magnets and planetary gear was designed. With the help of the developed algorithm and software transients of the electrical and mechanical quantities in the system: battery – car starter – combustion engine were computed. Circuit-field method was used. Transients in the analyzed system at different ambient temperature were determined. The parameters of the developed car starter excited by neodymium magnets were compared with the parameters of the car starter with ferrite magnets.

19

New approach to protecting transformers against high frequency transients – wind turbine case study

Smugała D., Piasecki W., Ostrogórska M., Florkowski M., Fulczyk M., Granhaug O.

Przegląd Elektrotechniczny

|

2013

|

R. 89, nr 10

186-190

EN

Novel protection method of wind turbine transformers against high frequency transients occurring during switchgear operation is described in this paper. Presented results are continuation of research on Very Fast Transients mitigation methods previously published in literature [8]. Principles of novel suppressing device parameters optimization for windmill transformers are also included. ATP-EMTP simulations results for wind farm application were verified by full scale functional tests.

PL

W artykule przedstawiono nową metodę ochrony transformatorów turbin wiatrowych przed wysokoczęstotliwościowymi przepięciami mogącymi wystąpić w trakcie ich pracy. Przedstawione rezultaty są wynikiem kontynuacji wcześniejszych badań prowadzonych nad ochroną transformatorów dystrybucyjnych przed zakłóceniami o wysokokiej częstotliwości mogącymi wystąpić w sieci SN [8, 9]. Wyniki symulacji przepięć oraz doboru parametrów urządzeń ochronnych, zostały zweryfikowane w trakcie testów funkcjonalnych.

20

Application of integral equations for analysis of electric circuit transients

Hamola O.

Przegląd Elektrotechniczny

|

2013

|

R. 89, nr 2a

256--258

EN

This paper discusses the particularities of integral equations for calculating the electric circuits transients with multiple switching. Each switching in some way affects constraining forces that is taken into account in certain correction of the right side of integral equation. The numerical method is used to solve integral equations.

PL

W pracy zbadano właściwości równań całkowych opisujących stan nieustalony w obwodach z wielokrotnym przełączaniem. Każde przełączenie powoduje modyfikację prawej strony równań. Pokazano metodę numeryczną rozwiązywania równań całkowych opisujących obwody.