Browsing by Author "Refoufi, Larbi"
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Item An adaptive threshold estimation scheme for abrupt changes detection algorithm in a cement rotary kiln(Elsevier, 2014) Kouadri, Abdelmalek; Bensmail, Abderazak; Kheldoun, Aissa; Refoufi, LarbiItem Analysis of the self-excited induction generator steady state performance using a new efficient algorithm(Elsevier, 2012) Kheldoun, Aissa; Refoufi, Larbi; Khodja, Djalal EddineThe paper presents the application of DIRECT algorithm to analyse the performance of the Self-excited induction generator (SEIG). To the author best knowledge, this is the first attempt to apply it to such a problem. DIRECT algorithm is used to minimize the induction generator’s admittance without the need to separate it into its real and imaginary parts. No initial guess is required as it needs only the upper and lower values of the unknown variables which are easily determined. The obtained minimum admittance yields the adequate magnetizing reactance and the frequency. These two key parameters are then used to compute the self-excitation process requirements in terms of the prime mover speed, the capacitance and the load impedance on the one hand and to predict the generator steady state performance parameters on the other. Very good agreement between predicted results and experimental measurements is achievedItem Application of new optimisation algorithm to self-excited induction generator analysis(IEEE, 2013) Kheldoun, Aissa; Refoufi, Larbi; Khodja, Djalal EddineItem An investigation into the effects of complex supply voltage unbalance on squirrel cage induction motors(2012) Refoufi, Larbi; Dekhandji, Fatma ZohraItem Large power transformer reliability modeling(Springer, 2016) Chafai, Mahfoud; Refoufi, Larbi; Bentarzi, HamidItem Large squirrel cage induction motor reliability modelling(2007) Chafai, Mahfoud; Refoufi, LarbiIn this study a simplified reliability model is developed on the basis of knowledge, from field data, of the dominating failure modes and mechanisms of large power squirrel cage induction motors operating at constant speed and fed from a conventional 3 phase sinusoidal supply voltage. Field data failures distribution indicates a dominance of failure modes pertaining to machine bearings and stator winding insulation. The motor system can be regarded as a complex combination of three fundamental parts: The stator, the rotor and the bearings which are respectively electrical, electromechanical and mechanical in nature. On this basis, the motor system reliability block diagram is modelled in a series configuration comprising the above mentioned parts. The individual reliability functions developed for each part will yield together the overall motor system reliabilityItem Performance of induction motor under the effect of voltage unbalance with loading consideration(Springer, 2015) Dekhandji, Fatma Zohra; Refoufi, LarbiItem Quantitative assessment of three phase supply voltage unbalance effects on induction motors(Springer, 2015) Dekhandji, Fatma Zohra; Refoufi, Larbi; Bentarzi, HamidItem Reliability assessment and improvement of large power induction motor winding insulation protection system using predictive analysis(2008) Chafai, Mahfoud; Refoufi, Larbi; Bentarzi, HamidThe paper presents a reliability assessment of a widely used protection system of large power squirrel cage induction motors. In conjunction with published field induction motors Failure data this assessment effort is based on a integrated predictive analysis using three methods: (1) a Fault Tree Analysis (FTA) that allows to identify and then quantify the initiating failure cause weighting factors; (2) an Event Tree Analysis (ETA) that allows to predict the protection system probability outcomes following an external disturbance and (3) a Failure Mode Effect and Criticality Analysis (FMECA) that will help set the stage for developing a preventive maintenance program fit to keep up the induction motor protection system reliability at the required level with particular attention given to aggressive environmental factors such as found in cement plantsItem Reliability estimation and enhancement of PLC relay output units using FMECA(2007) Chafai, Mahfoud; Refoufi, LarbiFailure Modes Effects and Criticality Analysis in association with reliability estimation using part count method, are used together to determine failures which may affect the relay output circuit of programmable logic controller (PLC) systems in a dusty cement industry. Once the critical points are identified, reliability enhancement measures are proposed in view of increasing the overall availability of the processItem Two approaches for direct torque control using a three-level voltage source inverter with real time estimation of an induction motors stator resistance(2007) Zaimeddine, Rabah; Berkouk, EL Madjid; Refoufi, LarbiItem Voltage unbalance effects on induction motor performance(2006) Refoufi, Larbi; Bentarzi, Hamid; Dekhandji, Fatma ZohraThe reliability of electric drives and driven motors depends on the quality of the power supply voltage especially in the critical industrial process. In this work, a theoretical study of the effects of voltage unbalances, sags and swells on induction motor (IM) is performed by using the conventional method based on the theory of symmetrical components. For this study, MATLAB software program is developed for calculating currents, torque, power losses, temperature rises and derating factor. Besides, experiments have been carried out for obtaining currents, torque and power losses. An agreement that is found between the theoretical predictions and experimental data allows us to take into consideration the predicted derating factor