Analyse statistique des évènements conséquents à un arc électrique amorcé par la présence d’un objet conducteur

Une analyse statistique est réalisée afin de déterminer les risques et les dommages provoqués par un arc électrique, engendré par la présence d’un Foreign Object Debris (FOD) entre deux pièces métalliques nues sous tension. La tension appliquée est de 400Vrms à 400Hz. Les mesures électriques sont corrélées à des observations par imagerie rapide afin d’associer les signaux électriques aux comportements de l’arc et du FOD. Trois types d’évènements ont été détectés à l’issu de la campagne d’essais : l’éjection du FOD, le soudage d’un côté et des deux côtés du FOD. En conclusion, nos mesures montrent que le type d’évènement dépend fortement du diamètre du FOD

Etude de l'interaction d'un arc électrique de faible puissance avec une onde électromagnétique dans un écoulement d'air à pression atmosphérique

ORSAY-PARIS 11-BU Sciences (914712101) / SudocSudocFranceF

Analyse statistique des évènements conséquents à la présence d’un objet conducteur entre deux électrodes

Une analyse statistique est réalisée afin de déterminer les risques et les dommages provoqués par un arc électrique, engendré par la présence d’un objet entre deux pièces métalliques nues sous tension. La tension appliquée est de 400 Vrms à 400 Hz. Les mesures électriques sont corrélées à des observations par imagerie rapide afin d’associer les signaux électriques aux comportements de l’arc et de l’objet. Trois types d’évènements ont été détectés à l’issu de la campagne d’essais : l’éjection de l’objet, le soudage d’un côté et des deux côtés de l’objet. En conclusion, nos mesures montrent que le type d’évènement dépend fortement du diamètre de l’objet

Study of electric arc ignition behavior and extinction in aeronautical environment in presence of FOD

—Current development of more electrical aircraft and future all electrical aircraft leads increased power densities and power on board. The increase in power densities take the form of increased voltage (230/400 Vac, ± 270 Vdc) and/or decreased distances between conductors. The addition of these evolutions leads to higher probability of electric arc, which might be potentially more destructive. In this paper electric arcs ignited by a Foreign Object Debris (FOD) that shorts out two busbars, are characterized. The electrical parameters meet the aeronautical standards, i.e. 230/400 Vac at 400 Hz. A statistical study of the impact of the FOD geometry on the arc size is carried out with the aim to give guidelines for the development of passive protections. The results show that there is no direct correlation between the arc dimensions and the FOD diameter or mass, although the object behavior was different. In a second part the electric arc was characterized in terms of dimensions over time and electrical signature to state on the time in which active protection should trip and to try to find a signature of the arc to detect. The results tend to prove that the dV/dt might be a relevant marker of the arc

Electric current partition during vacuum arc remelting of steel: An experimental study

International audienceThis paper describes measurements of the voltage and temperature profiles in a vacuum arc remelting (VAR) crucible during a series of melts of a 40CrMoV13-9 steel alloy electrode, which were used to obtain information about the current flows in the furnace. The results derived included the current leaving the crucible above the ingot crown, the current flowing between the crucible and the crown, the current transferred between the crucible and the ingot lateral surface and the current flowing through the ingot bottom. It was established that the crown (observed to be 5-10 cm high) played a predominant role in the current distribution, as the crown carried more than 50% of the furnace current. A small but non negligible fraction of the furnace current (about 10%), which represents the lower limit of the side-arcing current, was found to leave the crucible above the crown. The effect of the arc gap length on the current distribution was examined, but no general trend was clearly identified. Finally, a summary of the results reported in this study and those previously obtained in the literature is presented. Significant differences regarding the estimated amount of the side arcing current were noted that did not seem to be directly related to the changes in the remelted materials or melting conditions. It was pointed out that a detailed understanding of the current partition in the furnace requires additional experimental and theoretical study to clarify the path of the current flowing through the ingot crown

Optical investigation of the behavior of the electric arc and the metal transfer during vacuum remelting of a Ti alloy

International audienceHigh-speed camera imaging and optical emission spectroscopy have been used for investigating the structure of the electric arc and the transfer mechanisms of the liquid metal during vacuum arc remelting (VAR) of Ti alloys. The arc exhibited a similar operating regime,to that described in the previous literature for the case of Inconel 718 and zirconium alloy electrodes. The arc behaved in a diffuse mode with many separate and rapidly moving cathode spots. Several parameters of the cathode spots, including their current, size and apparent velocity were evaluated. The application of an external axial magnetic field tended to encourage the cathode spots to locate themselves on the base of the electrode. A large density ratio of Ti+ ions and Ti atoms in the interelectrode plasma was evaluated, suggesting that the plasma was strongly ionized. The calculated excitation temperature of Ti+ ions (1-1.2 eV) was about 1.5-2 times greater than that obtained for Ti atoms. The transfer mechanisms of the drops of liquid metal might be classified into three main modes depending on the gap length: drop falling, drip short and drop erosion induced by the cathode spots. The importance of the influence of the arc on the metal transfer mechanisms was inversely related to the gap length