Nowadays, numerical modelling has become an interesting tool for determining impedance variations due to various conductive flaws in eddy current nondestructive evaluation systems. These kinds of defects, rarely treated in the published works, are taken into consideration in the modelling while introducing them as electrically conductive volumes with a finite electric resistivity. This step is very important since it permits to improve qualitatively several models developed so far by many authors whose consider the defect as loss of material only. However, in several applications, the defect can occur with a finite resistivity such as impurity, small burns and micro-solder. On the other hand, even though the defect appears with a loss of materials, som e polluting materials can fill the affected region. Indeed, the volume of the initial defect will be completely or partially occupied by these conducting pollutant materials. This paper deals with the effect of physical and geometrical characteristics of such kind of defects on the differential sensor response. Furthermore, the necessity of taking the defect electric conductivity (as an important parameter) into account will be explained, in order to develop a reliable and accurate inverse method allowing a full characterization of conductive defects.

This study will focus on the investigation of the effect of electrical discharge on physical, chemical, electrical properties of transformer oil, and on the development of a mathematical model describing the gassing of insulating oil under electrical discharge, using the information contained in the measured values. For predicting the gassing tendency for extensive ageing periods, we use the model developed, for an intelligent system design. The predictor's parameters are chosen based on their influence degree by the electrical field. Various scenarios were considered. The study was carried on two types of fluids, under electrical stress for different ages. The 6802, 6181 and 924 ASTM tests methods were used for the measurements of parameters in degradation. All the results obtained are summarized and compared. The properties which are strongly dependent have been specified, a multiple linear regression model for each fluid as a function of its DDP, DDF, turbidity and aging period is developed. This model is for the estimation of the gas quantity cumulated under electrical discharge. The prediction is made, by implanting the stepwise regression results into a neural network system, which has been tested on experimental results obtained from laboratory samples, and high prediction accuracy has been achieved.

Rotating electrical machines play an important role in the industrial world. Among them, the three- phase squirrel cage asynchronous machines are frequently used because of their robustness, their relatively simple construction and their low cost. Nevertheless, during their lifespan, these machines are submitted to external and internal stresses which can lead to several failures. In this paper, we present the estimate of the parameters sensitive to the defects, namely the rotor currents and resistances of the rotor bars, by using the Extended Kalman filter.

This paper deals with the design of an integrated starter generator system for a car flywheel based on the Switched Reluctance Machine (SRM) technology. First, we discuss about the starter generator problematic following the results of our bibliography research, and secondly, we briefly remained generalities about the SRM and the determination of the laws control. In addition, we designed the converter associated to the machine using (Matlab/Simulink) software in order to identify the laws control and to adapt to the operating modes (motor, generator, booster, brake). Finally, simulations of the open and closed loop model were performed on the converter with machine (SRM).

This paper presents a new method combining sliding mode control (SMC) and fuzzy logic control (FLC) to enhance the robustness and performance for a class of non-linear control systems. This fuzzy sliding mode control (FSMC) is developed for application in the area for controlling the speed and flux loops of asynchronous motors. The proposed control law can solve those problems associated with the conventional control by sliding mode control, such as high current, flux and torque chattering, variable switching frequency and variation of parameters, in which a robust fuzzy logic controller replaces the discontinuous part of the classical sliding mode control law. Simulation results of the proposed FSMC technique on the speed and flux rotor controllers present good dynamic and steady-state performances compared to the classical SMC in terms of reduction of the torque chattering, quick dynamic torque response and robustness to disturbance and variation of parameters.

This article presents a defect modeling in eddy current non-destructive testing systems by using a new developed method called coupled electric field. It permits to improve qualitatively several models developed so far by many authors using coupled circuit methods that consider the defect only as loss of material. However, a defect can occur with a finite conductivity such as impurity, small burns and micro-solder. For this reason, this investigation consists of extending the coupled circuit method to the modeling of this kind of defects. The proposed approach consists of firstly considering the defect as an electric conductive volume and secondly changing the state variable presenting the electric current by the electric field one. This procedure permits expressing explicitly the impedance variation caused by the presence of an axi-symmetrical defect according to its characteristics. The comparison between the impedance variations calculated using finite elements method and the proposed one demonstrates a very good concordance. After this validation, the study covers also the influence of the defect shape and position on encircling probe impedance. This method is interesting since it permits a fully characterization of this kind of defects and facilitates the inversion process. Moreover, using a 3D finite element observation, this fast tool of simulation can be adapted for a fast phenomenological modeling of asymmetrical configurations.