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.