No abstract

In this paper we present a study concerning the influence of the electrode gap on the erosion of a copper cathode under the sole action of an electric arc in air at atmospheric pressure. The causes of the variations of the erosion rate with this parameter are studied. It is shown that, certainly, the variations of the erosion rates with the electrode gap should be imputed to two factors: the arc mobility which changes strongly with the electrode gap and a 'supplementary' heating of the cathode surface due to interactions that occur at small electrode gap values between the cathode surface and the anode plasma jets.

The aim of this paper is to improve our knowledge concerning the power balance at the electrode surfaces in the case of an electric arc of short duration with a small electrode gap burning in air at atmospheric pressure.With this aim in view, we propose a simple method using the experimental results obtained through the observation of the tracks left by the arc and a numerical simulation of the thermal phenomena occurring in the electrode during the arc heating.This method, based on the analysis of the compatibility between experimental results and modelling results, allows us to assess a zone of possible values for the main parameters of the arc root (power and surface power density brought by the arc to the electrodes). A simple usual volt equivalent approach of the power balance is proposed. Calculations and experiments have been conducted for several copper anodes and cathodes. The values for the volt equivalent at the anode are found in the range 9-12.6 V, for the cathode 5.4-9 V. The values for the surface power density are found to be near 6.5 × 10 9 W m −2 at the cathode and 6 × 10 9 W m −2 for the anode.

No abstract

This paper 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 (Ag, Ag-12wt%SnO 2 ), the value of the inductance in the electrical circuit. The measured parameters characterizing the opening phase are as follows: the arc duration, the value of the electrode gap when the arc extinguishes, the arc energy, the maximal value of the contact voltage during the opening phase, and the electrode erosion. The study of the erosion is achieved with the help of a 3-D profilometer enabling the measurement of mass transfer and, for instance, of the amount of molten or evaporated metal.Index Terms-Electric arc, electrical contacts, erosion, hybrid vehicle, 36-V dc.