The Experts below are selected from a list of 273 Experts worldwide ranked by ideXlab platform
A.s. Abdallah - One of the best experts on this subject based on the ideXlab platform.
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Saturated synchronous Reactances of synchronous machines
IEEE Transactions on Energy Conversion, 1992Co-Authors: A.m. El-serafi, A.s. AbdallahAbstract:The authors present a model for the d and q-axis synchronous Reactances in which the effects of both the d- and q-axis saturation factors and the cross-magnetizing phenomenon are included. The variations of the d- and q-axis mutual Reactances versus the d- and q-axis ampere-turns are also shown. The results obtained by using this model were found to be in good agreement with those measured experimentally. These results show also that the saturation effects on the d- and q-axis mutual Reactances could be large and its effect on the q-axis Reactance could be larger than that on the d-axis Reactance. The results demonstrate that the effect of the cross-magnetizing phenomenon could be appreciable and its negligence or improper representation could lead to inaccurate values for the machine Reactances. >
A.m. El-serafi - One of the best experts on this subject based on the ideXlab platform.
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Saturated synchronous Reactances of synchronous machines
IEEE Transactions on Energy Conversion, 1992Co-Authors: A.m. El-serafi, A.s. AbdallahAbstract:The authors present a model for the d and q-axis synchronous Reactances in which the effects of both the d- and q-axis saturation factors and the cross-magnetizing phenomenon are included. The variations of the d- and q-axis mutual Reactances versus the d- and q-axis ampere-turns are also shown. The results obtained by using this model were found to be in good agreement with those measured experimentally. These results show also that the saturation effects on the d- and q-axis mutual Reactances could be large and its effect on the q-axis Reactance could be larger than that on the d-axis Reactance. The results demonstrate that the effect of the cross-magnetizing phenomenon could be appreciable and its negligence or improper representation could lead to inaccurate values for the machine Reactances. >
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A new method for determining the armature leakage Reactance of synchronous machines
IEEE Power & Energy Magazine, 1991Co-Authors: A.m. El-serafiAbstract:A method for determining the armature leakage Reactance of synchronous machines is presented. In this method, the terminal voltage/armature current characteristic with the machine unloaded and unexcited is needed, together with the open-circuit characteristic of the machine. The armature leakage Reactance is derived from these two curves using an iterative technique. The armature leakage Reactances of five synchronous machines of different designs are obtained using this method. Their values are compared with those of the Potier Reactance of these machines measured at various terminal voltages. >
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A new model for the saturated synchronous machines using the intermediate-axis saturation characteristics
IEEE CCECE2002. Canadian Conference on Electrical and Computer Engineering. Conference Proceedings (Cat. No.02CH37373), 1Co-Authors: N.c. Kar, A.m. El-serafiAbstract:The effect of saturation in synchronous machines is usually represented in their two-axis frame models by using their saturated d- and q-axis synchronous Reactances. These saturated d- and q-axis synchronous Reactances are obtained by modifying their unsaturated values with appropriate saturation factors corresponding to the voltage behind the leakage Reactance. In practice, this technique fails to give good agreement to the measured values due to the fact that the cross-magnetizing effect (magnetic coupling between the direct and quadrature axes) is ignored In this paper, an innovative model for the saturated synchronous machines using the intermediate-axis saturation characteristics is proposed and, thus, the cross-magnetizing effect will be included explicitly. To verify the accuracy of this proposed approach, experimental investigations were carried out on a number of laboratory synchronous machines of different designs. The calculated field currents and load angles of these machines by the proposed approach have been compared with the measured ones.
Prabha Kundur - One of the best experts on this subject based on the ideXlab platform.
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Modeling effects of system frequency variation in long-term stability studies
IEEE Transactions on Power Systems, 1996Co-Authors: Rajiv K Varma, G J Rogers, R M Mathur, Prabha KundurAbstract:This paper describes a fundamental study into modeling the effects of frequency variation on network and shunt impedances in long term power system stability simulations. The focus is on extreme post-fault situations where significant generation-load mismatch causes wide excursions in power system frequency. A novel application of singular perturbations is presented. This method is compared with the "constant Reactance" technique, the "variable Reactance" method in which the network Reactances are varied with system frequency, and a method in which the network transients are fully simulated. Stability simulations for an interconnected two-area power system employing the different modeling techniques show that a two time scale analysis using the singular perturbation method is a feasible technique for accurate prediction of long term post fault system behaviour.
Yijun Feng - One of the best experts on this subject based on the ideXlab platform.
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Passive Metasurface for Reflectionless and Arbitary Control of Electromagnetic Wave Transmission
IEEE Transactions on Antennas and Propagation, 2015Co-Authors: Bo O. Zhu, Yijun FengAbstract:Electromagnetic (EM) wave propagation control is an important issue for both science and engineering. A metasurface is an artificial surface composed of electrically small scatterers. Of late, metasurfacing has been an emerging and promising technique for controlling wave propagation. Traditional metasurfaces mainly employ surface Reactances and generally reflect waves when manipulating wave transmission or refraction. In this paper, a passive metasurface employing both surface Reactance and positive surface resistance is proposed, which can not only manipulate wave transmission magnitude and phase independently and fully but also suppress wave reflection simultaneously. Furthermore, reflectionless refraction can also be achieved with the proposed passive metasurface. The complete design theory is established for the passive metasurface. Theoretical analysis, prototypes, simulation, and experimental validation are demonstrated. The reflectionless feature of a passive metasurface is important for avoiding multiple wave reflections and interference between stages in EM systems. It also enables novel wave transmission cascade manipulation and may have potential applications in highly directive radiation.
Li Ruo-mei - One of the best experts on this subject based on the ideXlab platform.
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Influence of Induction Motor Load Parameters on Power System Transient Voltage Stability
Power system technology, 2005Co-Authors: Li Ruo-meiAbstract:Taking simple power system as the subject investigated and using third-order model of induction motor load in which the electromechanical transient process is taken into account,the influence of the variations of transmission line Reactance,shunt capacitive Reactance on load bus and induction motor load parameters on critical clearing time of power system transient voltage stability is analyzed by time-domain simulation.The analysis results show that all of above-mentioned parameters have influence on power system transient stability,and the system transient stability is more easily influenced by transmission line Reactance,the proportion of induction motor load in total loads,stator Reactance,rotor resistance,rotor Reactance and initial rotor slip.
