R. Andlauer

High intensity contact opening under DC voltage

This work concerns the study of contact opening under DC voltage in the case of high intensity current (a few hundred amperes). The application fields are mainly automotive and aeronautical systems. An experimental device has been designed in order to study the opening of contacts under various conditions. The influence of several parameters on contact opening is studied. These are the following: the opening velocity, the current intensity through the closed contact, the nature of the contact materials (Cu, Ag, Ag-12 wt% SnO2), and the value of the inductance in the electrical circuit. The measured parameters characterizing the opening phase are: the arc duration, the contact resistance, the values of the electrode gap when the arc extinguishes, the arc energy and the electrode erosion. The structure and the behavior of the arc during the opening phase are investigated with the help of a high speed cinematography device. The study of the erosion is achieved with the help of a 3D profiler enabling the measurement of mass transfer and, for instance, of the amount of welded or evaporated metal. The use of a 2D numerical model of the thermal phenomena, induced by the arc at the contact opening, makes it possible to get interesting information concerning the power balance at the contact electrodes during the opening.

Contribution to the modeling of the heating phenomenon of electric contacts

In this paper we propose a 2D axisymmetric numerical modeling of the heating of cylindrical electrical contacts under the action of the current flow. The distributions of the electrical potential and of the temperature field in the contact bodies are calculated with the help of a finite-difference method. The modeling takes into account the temperature variations of material properties (electrical and thermal conductivity, specific heat...). Various phenomena are then studied for a copper contact such as the influence in stationary regime of the boundary conditions on the electrode heating and on the contact voltage drop (more particularly the role of heat exchange coefficient on the contact surfaces). A comparison with the usual Kohl-Rausch theory is then realized. Moreover, a study concerning the influence of the thermoelectric effect on heavy contact heating is presented in the stationary regime.

An original method to assess the surface power density brought by an electric arc of short duration, and short electrode gap to the electrodes-case of copper electrodes

In this paper, an original method is proposed in order to obtain an interval of possible values for the surface power density brought to the electrodes by an electric arc of short duration and short electrode gap. Results for copper electrodes are presented in the case of an electric arc in air at atmospheric pressure.