mounir gahgah - Academia.edu (original) (raw)

Papers by mounir gahgah

Active power filters are used to improve the energy quality of the electrical distribution networ... more Active power filters are used to improve the energy quality of the electrical distribution networks by the harmonic elimination and correcting of the power factor. However, many conventional configurations of active filters are constituted by a significant number of semiconductors that generate a crowded installation with a complicated control, high cost price of his designs and power losses due to switching of semiconductors. For these reasons, the innovation of these configurations is required. This article, presents a proposed structure of multilevel active power filter auto-rectifies with a reduced number of switches. It is controlled by an easy flowchart permitting a functioning fast and efficient to eliminate the named problems of traditional structures. The use of this structure also reduces to half the number of DC bus capacities of its supply. Conventional systems such as seven levels inverter NPC-type require twelve power switches, six capacities of DC bus and diodes of neutral point clamped. The proposed model retained its ability to produce the same seven levels of voltage with only a small number of eight bipolar switches, three capacities of DC bus and none diode used for the neutral point clamped. The simulation results illustrate an important reduction in THD of current supply from 25.35% to 1.82%, that's less significant than the value conform to IEEE standards of 5% with a good compensation of reactive power.

Every machine has mechanical moving parts in recent generate internal stresses in its structure. ... more Every machine has mechanical moving parts in recent generate internal stresses in its structure. These efforts are manifested by the vibration of the whole structure of the machine. For the collection of data necessary to analyze the origin of these efforts are often used vibration sensors, whose function is to transform mechanical energy into a proportionate and measurable electrical signal. In the present work, we limited our study to the search for the best position of the sensor and the measurement point of taking a significant vibration. For this, we considered nine measurements points regularly distributed over half the circumference (180°) of the driving motor of a motor-fan group mounted on flexible substrates, so measurement points that have a pitch equal to 22,5°. In this installation, we have identified three zones; A, B, and C there is seen that amortization is only provided and limited by zone B. The measurements made, have led us to confirm that the measurements points to this type group of motor-fan, will be performed on the horizontal plane and loins of the amortized zone B. In addition, we have taken for this analysis both measurement, one without unbalance and another with the presence of unbalance. In the end, the FFT calculation under Matlab software of the time signal data delevred by the sensor to an oscilloscope is used.

HAL (Le Centre pour la Communication Scientifique Directe), Mar 19, 2013

La maintenance prédictive est utilisée pour améliorer la disponibilité des organes industriels to... more La maintenance prédictive est utilisée pour améliorer la disponibilité des organes industriels tout en minimisant les coûts de la maintenance. Le suivi de l'évolution des défauts et la détection précoce s'appuient sur des contrôles périodiques afin d'éviter les pannes et pour en prévoir les opérations de maintenance jugées utiles dont le but de garantir un fonctionnement normal par la suite. Donc on parle de l'avenir en connaissant le présent. Dans ce contexte, nous sommes entrain de discuter un modèle stochastique basé sur une chaîne de Markov de type (X n , n = 1, 2, 3,….). C'est-à-dire, si X n = i alors le processus est dit à état i au temps n avec l'existence d'une probabilité P ij pour que ce processus sera dans l'état j au temps n+1. Ainsi, la distribution conditionnelle d'un futur état X n+1 est indépendante des états passés mais elle est dépendante seulement de l'état présent X n. Dans cette étude, nous avons présenté la méthodologie qui permet de modéliser l'évolution de la dégradation survenant dans les pièces mécaniques, le cas étudié il s'agit du processus de la dégradation des roulements à double rangées et qui sont installés sur des ventilateurs centrifuges de moyenne puissance. A chaque roulement, nous proposons d'associer une chaîne de Markov décrivant la transition d'un état (i) à un autre état (j) suite à l'évolution du niveau global de la vibration, sachant que d'après les normes (NF, ISO, VDI, API…) le processus de dégradation de l'importe quel organe mécanique passe par des états tels que: "Bon", "Admissible", "Encore admissible" et "Inadmissible". Le modèle proposé permet de calculer la probabilité d'avoir un roulement dégradé le long de sa durée de vie. De plus, il est possible d'utiliser la matrice de transition associée à la chaine de Markov dans le cadre d'une analyse de fonctionnement pour la détermination de la fiabilité d'un système mécanique.

Polymers, Jun 29, 2023

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

RECENT, Sep 24, 2018

We present in this paper the results of an experimental study conducted on the analysis of the cl... more We present in this paper the results of an experimental study conducted on the analysis of the clogging influence of a filter installed on the suction pipe, on the axial fan operating parameters. In this study, we used an axial fan driven by a variable speed electric motor. The filter used has a removable filter element, in this context, we tested five filter elements with different filter surfaces and this to model the effect of clogging the filter on the pressure losses generated at the level of the filter in question. To obtain a differential pressure gauge installed upstream and downstream of the filter is used, the pressure value detected by the latter characterizes the relationship between the filtering surface (the surface crossed by the air flow at the filter) and the singular losses. The tests were carried out for different flow rates and speeds. The results obtained clearly show the effect of the filter clogging on the operating parameters of the fan, and characterize the relationship of these parameters with local pressure losses.

Polymers

A designer of sustainable biocomposite structures and natural ropes needs to have a high confiden... more A designer of sustainable biocomposite structures and natural ropes needs to have a high confidence interval (95% CI) for mechanical characteristics data of performance materials, yet qualities for plant-based fibers are very diverse. A comprehensive study of the elements that enhance the performance of biocomposites or sustainable ropes created from vegetable fibers is necessary. The current study included five groups with varying numbers (N) of tests of 20, 40, 60, 80, and 100 on the mechanical characteristics at room temperatures. The purpose of this study was to determine how changing N affects the mechanical properties of sisal yarn. These properties include its strength, Young’s modulus, and deformation at rupture. A significance testing program including more than 100 tests was performed. Owing to the heterogeneity of the plant yarn, each group received more than 20 samples at a gauge length (GL) of 100 mm. The tensile strength characteristics of sisal yarns produced a wide r...

Abstract: In this work we have limited our study for the characterization of the influence of un... more Abstract: In this work we have limited our study for the characterization of the influence of unbalance on the vibratory level of a motor- fan. In this context, we proceeded to create a mechanical imbalance, by adding a mass on the rotating part of the system. This causes a centrifugal force, which causes internal stresses, affecting the proper operation of the machine. The calculation of the FFT of each signal is performed by MATLAB software, which allows the temporal phenomenon to be properly presented in a frequency domain. The various measurements of the vibration amplitude will be analyzed by the Taguchi method, which helps to minimize the effect of unbalance on the motorized fan. Key words: Motorized fan, unbalance, vibration, internal forces, Taguchi method.

The use of more and more electronic power switches with a nonlinear behavior generates non-sinuso... more The use of more and more electronic power switches with a nonlinear behavior generates non-sinusoidal currents in distribution networks, which causes damage to domestic and industrial equipment. The multi-level shunt power active filter is subsequently shown to be an adequate solution to the problem raised. Nevertheless, the difficulty of adjusting the active filter DC supply voltage requires another technology to ensure it. In this article, a photovoltaic generator is associated with the DC bus power terminals of the active filter. The proposed system consists of a field of solar panels, three multi-level voltage inverters connected to the power grid and a non-linear load consisting of a six-diode rectifier bridge supplying a resistive-inductive load. Current control techniques of active and reactive power are used to compensate for both harmonic currents and reactive power as well as to inject active solar power into the distribution network. An algorithm of the search method of t...

Le Centre pour la Communication Scientifique Directe - HAL - Université de Nantes, Mar 19, 2013

Predictive maintenance is used to improve the avai l bility of industrial bodies while minimizing... more Predictive maintenance is used to improve the avai l bility of industrial bodies while minimizing main tenance costs. Monitoring the evolution of defects and earl y detection are based on periodic controls to avoid failures and to plan maintenance operations considered relevant whi ch aims to guarantee normal operation later. So tal king about the future is knowing the present. In this context, a stochastic model is discussed ba sed on a type of Markov chain ( Xn, n = 1, 2, 3). That is, if Xn = i then the process is said to state i at time n with the existence of a probability Pij that this process will be in State j at time (n + 1). Thus, the conditional distribution of a futu re state of Xn+1 is independent of the past but only the Xn present state-dependent States. In this study, is presented the methodology to mode l and simulate the evolution of the degradation occ urring in mechanical parts, the cases studied its double row bearings installed on centrifugal fan of average po w...

Résumé-- La maintenance prédictive est utilisée pour améliorer la disponibilité des organes indus... more Résumé-- La maintenance prédictive est utilisée pour améliorer la disponibilité des organes industriels tout en minimisant les coûts de la maintenance. Le suivi de l’évolution des défauts et la détection précoce s’appuient sur des contrôles périodiques afin d’éviter les pannes et pour en prévoir les opérations de maintenance jugées utiles dont le but de garantir un fonctionnement normal par la suite. Donc on parle de l'avenir en connaissant le présent. Dans ce contexte, nous sommes entrain de discuter un modèle stochastique basé sur une chaîne de Markov de type (X n, n = 1,

RECENT - REzultatele CErcetărilor Noastre Tehnice, 2018