This paper deals with an implementation of a stator flux oriented method on a DSP board to drive an induction motor. This method is based on the integration of EMF directly provided by two extra coils located on the equivalent /spl alpha/, /spl beta/ reference axes of the stator. The open-loop integration problem is solved thanks to an online offset compensation algorithm which offers robustness especially at low speed. Experimental results of speed control are presented and commented to show the effectiveness of this method.
The influence of the startup instant of the quench in a superconducting current limiter is studied. The heat transfer equation is numerically solved, using the finite difference method, and taking the effects of current sharing into account. The results show the importance of this instant on the dissipated power, the temperature-increase and on the efficiency of the current limitation.
Superconducting Magnetic Energy Storage can be used to produce very high pulsed power peak. A superconducting coil is magnetically coupled with another coil linked to the load. During the storage phase, the current is constant. In order to transfer the energy to the load, we cause the quench of the superconducting coil. It is very important to know the efficiency of the transfer and how much energy is discharged in the Helium vessel. In this paper, we propose an analytical method which enables us to calculate very quickly the electrical parameters of such a device.
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Dans les zones littorales soumises à defortes marées, sont apparues de nombreuses perturbations ou ruines d'ouvrages induites par des contraintes océaniques.Si les conséquences nuisibles de l'agitation de la houle ne tardent pas à apparaître sur la carapace des ouvrages, la marée a un impact différé et peut engendrer des désordres majeurs aussi bien au niveau du noyau de l'ouvrage qu'au niveau de la carapace.Des affouillements locaux ont ainsi été observés au pieds des talus d'estran, mais aussi des ruptures en grand glissement causées par la marée.Depuis plusieurs années, l'étude de stabilité de pentes n'a pas cessé d'être affinée par différents développements, par contre l'influence du niveau piézométrique dû à la marée dans les calculs de stabilité de talus d'estran n'a jamais été abordée.A partir d'un code numérique de stabilité de pentes (PETAL du L.C.P.C.) on utilise la méthode des perturbations pour caractériser les lignes de glissement et pour définir le coefficient de sécurité associé.Dans le but de nous permettre de prendre en compte l'influence d'un cycle de marée sur la stabilité d'une pente, nous évaluons l'augmentation du risque engendré par l'action hydraulique cyclique de la marée.Différents cas, avec un sol de référence, ont été étudiés en faisant varier d'une part la pente du talus et d'autre part le niveau d'eau établi dans le massif.L'utilisation de l'outil numérique a permis de quantifier l'influence de la marée, à différents instants du cycle, sur le coefficient de sécurité au grand glissement d'un talus estuarien semiimmergé.Les résultats obtenus montrent une réduction significative du coefficient de sécurité et mettent en évidence l'importance de la prise -en compte de la marée dans les calculs de stabilité des talus d'estran.
This paper deals with instrument fault detection within a reconfigurable vector control scheme of induction motor. Current sensors failures are detected and reconfiguration of current measurement is achieved in order to allow continuous operation of the vector control. Simulation and experiments using a 5.5 kW machine are used to verify the theory.
An original method to compute a superconducting screen is considered. It is shown that this problem is equivalent to a magnetostatic inverse problem, which is solved using a genetic algorithm. This method is appropriate to superconducting films of any shape hecause only surface currents are to be considered for superconducting materials. To illustrate the method two examples are presented.
A superconducting magnet energy storage (SMES) can be used as a pulsed power supply. A superconducting coil stores energy without electrical losses and this energy can be recovered through a second wire on which the charge (electromagnetic launcher, for example) is linked. The design of such an apparatus needs to solve simultaneously thermal, magnetic, and electric equations. We proposed a three-dimensional finite difference method to solve these coupled problems. This tool enables us to describe resistive zones of expansion in thick coils during a quench and to predict the duration and the efficiency of the discharge. Moreover, it indicates if the coil is prevented from an excessive temperature increase. Then, a probative device is described and experimental results are compared with theoretical ones.
This study demonstrates the conversion of agricultural and industrial waste into construction materials by developing ultra-high-performance concrete using cold-bonded sesame ash and waste glass aggregates. The primary focus of this study was sustainability and waste valorization in self-curing concrete systems. This study focuses on many aspects of producing cementless concrete with superior short- and long-term properties, incorporating an innovative artificial aggregate premanufactured using sesame ash and waste glass. Prepacking technology of casting was used. A self-curing additive is used to reduce the energy required for curing. In cold-bonded aggregates (CBAs), the aggregate content ranged from 10 to 50% of the total sand volume. Polyethylene glycol was used as an internal curing agent to evaluate the mechanical properties of the concrete, including the compressive strength and tensile strength at different ages. The durability characteristics of the concrete were also analyzed in terms of its resistance to sulfates, chloride ion penetration, and performance at elevated temperatures of 300 and 600 °C. Microscopic analyses were conducted by scanning electron microscopy (SEM), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), and Differential Scanning Calorimetry (DSC). The results showed a significant improvement in the mechanical and durability performance, especially at 30%, which resulted in the highest compressive strength of 147.2 MPa at 90 days. This is an 11.93% increase compared with that of the reference mix. The tensile strength was also improved by 14.5% at the same replacement ratio. The mix containing 30% manufactured aggregate demonstrated the best thermal resistance, retaining the highest percentage of residual strength at both 300 °C and 600 °C, as well as superior sulfate impact resistance, with a strength reduction factor of 39.5%. When the replacement ratio was increased to 50%, the chloride penetration resistance improved significantly by 41% compared with that of the reference mix. FTIR, TGA, and DSC analyses also demonstrated enhanced silicate polymerization and increased carbonate formation, contributing to the improved chemical stability and density of the concrete matrix.
