STM Journals Peer-reviewed research from Consortium e-Learning Network

26 publications

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    Analysis of Six-Pulse Bridge Circuits Including Zener and Semiconductor Diodes – Part Two

    By Mohamed Mostafa Saied

    Abstract: The present study offers a generic method for simulating and modelling six-pulse rectifier bridge circuits in the time domain. These circuits can include Zener and/or semi-conductor type diodes or even a mixture of them. The governing system of simultaneous algebraic and differential equations are listed and solved numerically using a computer code written in Mathematica. The flexibly written program can handle voltage sources of any time waveform, frequency or internal …

    Published in Journal of VLSI Design Tools and Technology · Vol. 12, Issue 2, 2022 · pp. 13–21 Read article

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    Transient Analysis of Electronic Circuits Including Zener Diodes

    By Mohamed Mostafa Saied

    Abstract: This paper addresses the transient analysis of the electronic circuits incorporating Zener diodes. It starts with suggesting a new Zener diode model. The model is based on efficiently utilized step functions of the applied voltage. It includes also the diode’s main technical parameters such as its resistances in both the forward and reverse current directions as well as its Zener’s breakdown voltage. The sharp discontinuities of the step-functions are dealt …

    Published in Journal of VLSI Design Tools and Technology · Vol. 11, Issue 3, 2021 · pp. 1–9 Read article

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    Transient Analysis of Non-Uniform Windings or Lines with Non-Linear Termination

    By Mohamed Mostafa Saied

    Abstract: The paper deals with the transient analysis of non-uniform transmission lines and machine windings with non-linear terminations. The proposed time-domain technique is characterized by a relatively small computational burden. The analytical solution of the derived system of simultaneous differential and algebraic equations is done in Mathematica. The procedure is applied to several representative case studies involving line and winding non-uniformity and/or the non-linearity of the load termination, such as diodes …

    Published in Journal of VLSI Design Tools and Technology · Vol. 11, Issue 2, 2021 · pp. 42–50 Read article

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    Efficient Technique for Analyzing Non-Uniform Transformer Windings

    By Mohamed Mostafa Saied

    Abstract: This paper addresses the electromagnetic transients and the frequency characteristics of non-uniform transformer windings exhibiting inter-winding mutual circuit parameters. The dependence of the winding inductances and capacitances on the location along the winding is incorporated in the governing Kirchhoff’s voltage and current equations with the voltages and currents as unknowns. These unknowns will then be determined through the application of algebraic solution techniques in order to get closed-form analytical voltage …

    Published in Journal of Power Electronics and Power Systems · Vol. 11, Issue 3, 2021 · pp. 1–8 Read article

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    Analysis of the Current Chopping and Breaker Stresses in Electric Power Networks

    By Mohamed Mostafa Saied

    Abstract: This paper addresses the phenomenon of current chopping in electric power networks and the resulting circuit breaker transient recovery voltage. Its dependence on the pre-interruption loading conditions and the data of the power network is demonstrated. A Laplace-domain model with normalized network circuit parameters is adopted and a closed-form expression for the recovery voltage is derived. A numerical Laplace inversion technique using Mathematica is implemented in order to get its …

    Published in Trends in Electrical Engineering · Vol. 11, Issue 2, 2021 · pp. 1–11 Read article

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    Circuit Breakers’ Recovery Voltage Transients: Impact of Composite Loads and Power Network’s Configuration

    By Mohamed Mostafa Saied

    Abstract: The paper addresses the identification of the circuit breaker transient recovery voltage and its dependence on the loading conditions and the data of the power network, such as its rated power frequency and short-circuit level. A Laplace-domain approach is adopted and a closed-form expression for the recovery voltage is derived. A numerical inversion technique using Mathematica is implemented in order to get its time waveform. The proposed technique is applied …

    Published in Journal of Power Electronics and Power Systems · Vol. 11, Issue 2, 2021 · pp. 18–26 Read article

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    On The Energization and Steady-State Performance of 6-Pulse Diode Bridge Rectifiers Supplying Constant Voltage Loads

    By Mohamed Mostafa Saied

    Abstract: The paper addresses the analysis of 3-phase 6-pule diode bridge rectifier circuits supplying a special load category representable by constant voltage sources. The applied Mathematica-based solution technique can handle symmetrical and unsymmetrical 3-phase voltages. The presented results include the phase currents on the AC side as well as the magnitude and wave shape of the output current on the DC side. Several case studies demonstrating the impact of the source’s …

    Published in Trends in Electrical Engineering · Vol. 11, Issue 1, 2021 · pp. 14–23 Read article

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    Modeling and Simulation of a Chaotic Oscillator Using Mathematica

    By Mohamed Mostafa Saied

    Abstract: This paper suggests a modified methodology for the modeling and simulation of a chaotic oscillator. Its analysis and the pertinent results of an efficient Mathematica simulation program dealing with a typical Chua's circuit are presented and discussed. The derived computer code is based on the application of state-variables in the time domain. The program yields the circuit’s currents and voltages and indicates their sensitivities to changes in the numerical values …

    Published in Journal of Power Electronics and Power Systems · Vol. 11, Issue 1, 2021 · pp. 28–37 Read article

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    Steady State and Transient Analysis of 6-Pulse Rectifier Bridges Including Faulty Diodes

    By Mohamed Mostafa Saied

    Abstract: This paper addresses the steady-state and transient responses of un-controlled faulty 6-pulse diode rectifier bridge circuits. The faulty bridges can include several simultaneous diode valves’ open- or short-circuits. An efficient representation of the diodes is adopted in order to describe their performance in both the forward and reverse directions. A set of simultaneous differential and algebraic equations simulating the faulty rectifier bridge is presented. Its numerical solution is obtained through …

    Published in Journal of Power Electronics and Power Systems · Vol. 10, Issue 3, 2020 · pp. 19–31 Read article

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    Transients of Short-Circuits and Fault Clearance in 6-Pulse Diode Rectifiers

    By Mohamed Mostafa Saied

    Abstract: The paper addresses the short-circuit transients in 6-pulse diode rectifier bridges. It includes also an investigation into the transients resulting from the subsequent fault clearance. Unit-step functions are efficiently used for representing the diode characteristics and emulating the fault switching actions. The short-circuit fault and its subsequent clearance are simulated by means of a time-dependent shunt resistance at the rectifier terminals. The governing set of simultaneous algebraic and differential equations …

    Published in Trends in Electrical Engineering · Vol. 10, Issue 3, 2020 · pp. 6–14 Read article

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    Harmonic Analysis of 6-Pulse Diode Bridge Rectifier Circuits

    By Mohamed Mostafa Saied

    Abstract: This paper analyzes the steady-state harmonic performance of the six-diode, 3-phase rectifier bridge circuits. A procedure for determining the frequency spectra of the different voltages and currents within the bridge circuit, resulting from a 60-Hz 3-phase supply, is presented. The effect of the smoothing shunt-capacitor is also demonstrated. Based on a Mathematica code, the paper presents the results of a comprehensive list of case studies. The procedure can handle unsymmetrical …

    Published in Journal of Power Electronics and Power Systems · Vol. 10, Issue 2, 2020 · pp. 1–10 Read article

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    Harmonic Analysis of Full-Wave Diode Bridge Rectifier Circuits

    By Mohamed Mostafa Saied

    Abstract: This paper analyzes the steady-state harmonic performance of four-diode, single-phase full-wave rectifier bridge circuits. The frequency spectra of the source and load currents are presented. The effect of the load resistance, the source inductance, the smoothing shunt- capacitor as well as the waveform of the supply voltage is illustrated. The approach can also handle cases involving non-sinusoidal sources and non-linear loads. Based on a Mathematica code, the paper presents the …

    Published in Trends in Electrical Engineering · Vol. 10, Issue 1, 2020 · pp. 7–21 Read article

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    The Analysis of Bridge Rectifier Circuits using Mathematica

    By Mohamed Mostafa Saied

    Abstract: This paper addresses the steady-state and transient analysis of bridge rectifiers. It starts withsuggesting an efficient representation of the diodes. A single equation that describes thediode’s performance in both the forward and reverse directions is presented. It implicitlytakes the voltage polarity into account. Without any loss of generality, the suggested method isapplied to the classical uncontrolled four-valve full-wave rectifier bridge configureuration.The effect of the load resistance and the eventual presence …

    Published in Trends in Electrical Engineering · Vol. 10, Issue 1, 2020 · pp. 30–42 Read article

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    The Energization Transients of 6-Pulse Rectifier Circuits

    By Mohamed Mostafa Saied

    Abstract: This paper addresses the energization transients of 6-pulse rectifier circuits. It applies anefficient representation of the diodes in order to describe their performance in both theforward and reverse directions. Without any loss of generality, the suggested method isapplied to the classical un-controlled six-valve full-wave rectifier bridge configuration. Theeffect of the load resistance, the eventual presence of smoothing shunt-capacitors and seriesinductors as well as the waveform of the supply voltage is …

    Published in Journal of Power Electronics and Power Systems · Vol. 10, Issue 1, 2020 · pp. 18–30 Read article

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    A New Approach to the Laplace-Domain Transient Analysis of Non-Uniform Lines with Application to Power Line Towers

    By Mohamed Mostafa Saied

    Abstract: Abstract:This paper presents a new technique for the Laplace-domain analysis ofthe electromagnetic transients in non-uniform lines with special consideration of high voltage power line towers. The derived partial differential equations governing the voltage and current distributions, as functions of both the location and time, are solved by an efficient Mathematica computercode based on parametric functions. The applicability of the proposed direct distributed-parameter simulation is demonstrated. Theresults are in good agreement …

    Published in Trends in Electrical Engineering · Vol. 9, Issue 3, 2019 · pp. 1–10 Read article

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    Frequency Characteristics and Transient Response of Transmission Lines with Longitudinally Varying Ambient Temperature

    By Mohamed Mostafa Saied

    Abstract: This paper addresses the steady state, the frequency characteristics and the transient response ofpower lines in the presence of longitudinally varying ambient temperature. This variation willlead to location-dependent line circuit parameters and to a changing equivalent circuit. Thederived models, which are based on the exact long line theory, can incorporate the impact of thedifferent patterns of the temperature distribution in terms of location and magnitude. Severalcase studies of the resulting …

    Published in Journal of Power Electronics and Power Systems · Vol. 9, Issue 3, 2019 · pp. 19–30 Read article

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    New Method for the Transient Analysis of Lines with Corona

    By Mohamed Mostafa Saied

    Abstract: Abstract-- A new direct procedure for the transient analysis of overhead lines under corona is suggested.The governing partial differential equations are derived taking into consideration the possiblevariations in the line’s equivalent conductance and capacitance. A noniterative solution ofthese equations can be found in terms of interpolating functions resulting from a Mathematicacomputer code. The developed program can handle any time waveform of the sourcesinitiating the transients, any line length, design and …

    Published in Journal of Power Electronics and Power Systems · Vol. 9, Issue 3, 2019 · pp. 1–9 Read article

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    Modeling of Transformer Windings having Non-uniform Inductance Distribution

    By Mohamed Mostafa Saied

    Abstract: A direct analytical procedure for analyzing power transformer windings with location-dependent series inductance is presented. This dependence is typically introduced in order to take the inter-turn mutual inductive coupling into consideration. The paper addresses the frequency domain analysis conducted in the complex s- or the jω-domains. Results for the frequency-dependent winding’s input impedance with different treatments of the transformer’s neutral point will be available. The frequency characteristics including the resonance …

    Published in Journal of Power Electronics and Power Systems · Vol. 4, Issue 3, 2014 · pp. 12–25 Read article

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    The Frequency Characteristics of Transformer Windings Considering the Separation-Dependence of the Inter-Turn Mutual Parameters

    By Mohamed Mostafa Saied

    Abstract: The paper presents a direct method for the determination of the frequency characteristics of transformer windings. The dependence of both the inter-turn mutual inductances and capacitances on the separation between these winding turns is taken into consideration. From measured data available in the literature, a formula for this dependence is derived. The voltage and current distributions along the winding will be governed by two integro-differential equations in terms of the …

    Published in Journal of Power Electronics and Power Systems · Vol. 6, Issue 3, 2016 · pp. 72–81 Read article

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    An Analytical Method for the Analysis of Transformer Windings Having Non-Uniform Capacitance Distribution

    By Mohamed Mostafa Saied

    Abstract: A direct procedure for the transient and frequency analysis of transformer windings with location-dependent inter-turn capacitance distribution is presented. This can help simulate windings with non-uniform insulation. The derived analytic solutions in the Laplace domain are based on expressing the non-uniformly-distributed series capacitance per unit length as the sum of a constant term and a variable part proportional to the square of the distance from the winding’s source terminal. The …

    Published in Journal of Power Electronics and Power Systems · Vol. 5, Issue 2, 2015 · pp. 41–54 Read article

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