Modelisation de l'erosion des contacts sous l'effet de l'arc electrique des interrupteurs basse tension alternative

This work focuses on the modelling of contact erosion under the effect of electrical arc, for ac low voltage switches. Its objective is the estimation of the minimal life time of this type of switches. Because of the difficulty of this modelling, two approaches were adopted, an empirical approach and a mathematical one. The first one is based on the measurement of contacts mass variation (mobile contact and fixed one) after endurance tests witch are performed up to 25000 opening/closing cycles. The second one is based on the calculation of mass loss of contacts as a function of opening/closing cycles. Calculation is based on the heat conduction equation. A comparison between the two approaches has been done and justifications of the differences found have been presented. Because for real tests, there is not only mass loss, but other phenomena such as redeposit of material after evaporation and solidification, oxidation phenomenon, transfer of material from one contact to the other and finally contamination of contacts by carbonaceous deposit, due to electrical arc, coming from the electrically insulated wall of the switch. This last phenomenon has sometimes masked the real contact mass loss due to the electrical arc. With these approaches, it has been shown that it is easy to mathematically estimate the minimal life time of the switches and avoid expensive tests.