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Wyświetlanie 1-6 z 6
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:
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 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:
Transformer Modelling for the Frequency and Transient Analyses, with Non-Uniform Inductance Emulating the Inter-Turn Magnetic Coupling
Autorzy:
Saied, M. M.
Powiązania:
https://bibliotekanauki.pl/articles/262677.pdf
Data publikacji:
2014
Wydawca:
Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie
Tematy:
distributed parameter circuits
frequency response
modeling
power system transients
power transformers
resonance
non-uniform
Opis:
A new procedure for analyzing power transformer windings with location-dependent circuit parameters, such as the series inductance, is presented. This dependence is introduced in order to take the inter-turn mutual inductive coupling into consideration. It can be expressed either by analytical expressions or even in a tabulated form. The paper addresses both the frequency and time domain analyses. They are based on replacing the winding by an adequate number of equivalent cascade connected two-ports. In contrast to the usual practice of applying the simple medium line representation, each of these two-ports is treated as a long transmission line. Their A, B, C, D generalized circuit constants will be therefore generally location-and frequency-dependent. The analyses will be conducted in the complex s-domain. The corresponding time-domain results can then be obtained by applying a numerical inverse Laplace transform. Expressions for the winding’s input impedance with different treatments of the transformer’s neutral point will be derived for any assumed number of the equivalent two-ports. Results pertinent to the frequency characteristics including the resonance frequencies are presented. The paper also describes the winding’s transient response to the application of two standard voltage stimuli. The suggested approach is validated by its application to a case study for which an analytical closed-form solution is available. The analysis of windings exhibiting nonuniformities in more than one equivalent.
Źródło:
Electrical Power Quality and Utilisation. Journal; 2014, 17, 1; 1-11
1896-4672
Pojawia się w:
Electrical Power Quality and Utilisation. Journal
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Transient Performance of Partially-Undergrounded Overhead Lines in the Presence of Corona
Autorzy:
Saied, Mohamed M.
Powiązania:
https://bibliotekanauki.pl/articles/262791.pdf
Data publikacji:
2019
Wydawca:
Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie
Tematy:
distributed parameter circuits
non-uniform lines
power transmission lines
line modeling
transients
power networks
mixed
overhead-cable lines
partial undergrounding
distributions
mathematica
Opis:
The paper presents a method for investigating the electromagnetic transients of partially under-grounded high voltage overhead transmission lines in the presence of corona. It is based on a time domain model in which the corona is simulated by distributed voltage-dependent shunt current sources. The line segments and the inserted cable section are represented by a single equivalent transmission element having location-dependent circuit parameters per unit length. The numerical solution of the resulting set of differential equations yields the distributions of the voltage, the longitudinal current and the shunt corona current (per unit length) as functions of location and time. The presented two-, three-dimensional and contour plots proved to be helpful in discussing these distributions and in identifying any eventual current and/or voltage concentrations. The developed computer code in Mathematica can handle any time waveform of the source initiating the transients, any line termination as well as any lengths of the overhead line and cable section.
Źródło:
Electrical Power Quality and Utilisation. Journal; 2019, 21, 1; 1-8
1896-4672
Pojawia się w:
Electrical Power Quality and Utilisation. Journal
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A new closed loop speed control strategy for a vector controlled three-phase induction motor drive
Autorzy:
Tripathi, A.
Dey, A.
Dwivedi, B.
Singh, B.
Chandra, D.
Powiązania:
https://bibliotekanauki.pl/articles/262777.pdf
Data publikacji:
2008
Wydawca:
Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie
Tematy:
space vector modulation
VSI
induction motor model
transients
steady state value
Opis:
This paper presents a completely mathematical equations based model on control of torque and speed of a three-phase indirect vector controlled VSI fed cage induction motor drive that is controlled through the space vector modulated method. This enables a wide range of acceptability of the model for various values of load and for various types and ratings of induction motors. The uniqueness of the model lies in the fact that the deviations in the torque and speed on sudden application of reference step change in speed values are minimum i.e. when any sudden change in the speed reference is desired, the speed and torque waveforms reveal that the time taken in coming back to their final steady state values is very less and the motor overcomes the perturbation with negligible transients. The same is verified through the simulated results.
Źródło:
Electrical Power Quality and Utilisation. Journal; 2008, 14, 1; 67-72
1896-4672
Pojawia się w:
Electrical Power Quality and Utilisation. Journal
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-6 z 6

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