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Symmetrical power factors and symmetrical reactive current components
, Article 2006 IEEE Power Engineering Society General Meeting, PES, Montreal, QC, 18 June 2006 through 22 June 2006 ; 2006 ; 1424404932 (ISBN); 9781424404933 (ISBN) ; Karimi, H ; Sharif University of Technology
IEEE Computer Society
2006
Abstract
This paper deals with the definition of power factor and reactive current component in a three-phase system. For a single-phase system, power factor and reactive current component are defined based on the phase-angle displacement between the measured voltage and current waveforms. This definition can be directly extended to balanced three-phase systems. However, this extension is not suitable when the three-phase system (voltages or currents) is unbalanced. Reason is that the conventional definition of phase-angle does not directly apply to an unbalanced three-phase system and needs further refinements. This paper defines the concept of symmetrical power factors and symmetrical reactive...
Analysis of the power transfer to a nonlinear transmission line
, Article IEEE Transactions on Microwave Theory and Techniques ; Volume 65, Issue 11 , 2017 , Pages 4073-4083 ; 00189480 (ISSN) ; Hashemi, S. M. A ; Sharif University of Technology
Abstract
The input current of a nonlinear transmission line (NLTL), driven by a step voltage pulse, was analyzed theoretically. As specific results of the analysis, two basic parameters of NLTLs were formulated for the first time: the energy injected to NLTLs and their characteristic impedance. The energy delivered to an NLTL by a square voltage source, with a series resistance of RS, is given by a closed-form formula, which depends on the NLTL parameters and the input pulse characteristics. Considering the importance of the problem of the determining the injected energy content in a wide variety of the different applications of NLTLs, the obtained result will be of great importance, facilitating the...
Direct torque control of four-switch three phase inverter fed induction motor using a modified SVM to compensate DC-link voltage imbalance
, Article 2009 International Conference on Electric Power and Energy Conversion Systems, EPECS 2009, 10 November 2009 through 12 November 2009, Sharjah ; 2009 ; 9789948427155 (ISBN) ; Zolghadri, M. R ; Sharif University of Technology
Abstract
In this paper the direct torque control (DTC) of the induction motor fed by four switch three phase inverter (FSTPI) is investigated. A modified space vector modulation (SVM) approach with optimal voltage vector sequence is proposed to compensate the effect of dc-link voltage variations caused by circulating phase current through the capacitor bank. SVMDTC scheme of FSTPI fed induction motor is based on stator flux oriented control. According to simulation results, this approach significantly reduces the effect of dc-link voltage variation on the output torque, flux and current waveforms
Desgin and Implementation of Integrated Class EM Power Amplifier at 2.4 GHz
, M.Sc. Thesis Sharif University of Technology ; Medi, Ali (Supervisor)
Abstract
This project proposes a novel design technique for implementation of class-EM power amplifier (PA). Class-EM mode of operation has been proposed as the improved version of class-E; outclasses in terms of efficiency as well as power gain. Specifically, provided that the current fall time of switch is an appreciable portion of a period; frequency of operation is high enough that the switching time of transistor can no longer be considered instantaneous in other words. A novel technique for harmonic injection required for class-EM operation is proposed. Followed by the system of equations and the design methodology governing the proposed circuit. As a proof of concept and verification of the...
Three dimensional analysis of an AC electric arc furnace
, Article IECON Proceedings (Industrial Electronics Conference), 3 November 2009 through 5 November 2009 ; 2009 , Pages 3697-3702 ; Nazari, A ; Ataei, M ; Khademhosseini Beheshti, H ; Karimi, H ; Sharif University of Technology
Abstract
AC electric arc furnaces (EAFs) highly reduce power quality of the network by generating disturbances such as flicker and harmonics. These disturbances are due to the nonlinear electromagnetic and thermal field behaviors of the AC arcs. Analysis of these nonlinear behaviors is required for improving power quality in the network. This paper presents a three-dimensional finite element modeling of the electromagnetic fields in an AC three-phase electric arc furnace. The model includes the electrodes, arcs and molten bath. Current density, voltage and magnetic field intensity in the arcs, molten bath and electrodes are predicted as a result of applying the three-phase AC voltages to the EAF....