:The phenomenon of arcing is the major cause of electrical contact degradation in electrical switches. Degradation involves contact erosion and/or welding. The use of special contact material and that of specific material processing may permit contact erosion to be reduced, in particular by shortening the arc duration. A short review of these approaches is presented in the first part of this paper. In the second part, the development of a new self-blowing contact material is described. This material has been tested under DC voltages from 14 V to 42 V. A reduction of the arc duration by a factor of 4 approximately was obtained as was a concomitant reduction of the extinction gap to less than 2 mm. This material will contribute to achieving better reliability in high current-high voltages breaking devices, and will aid in their miniaturization, e.g. in relays.
International audienceIn order to fulfill the increasing electric power needs in automobiles and to satisfy new environmental requirements and security, the currently used 14 VDC electrical power systems must either supply higher currents (up to 100 A) or be changed to 42 V. Considering the difficulties of operating with this new 42 V system, we have focused our interests on higher currents by extending our previous 14 VDC study. The arc parameters such as break arc duration and extinction gap for different materials and circuit loads are investigated. We have established that these main arc parameters are greatly influenced by load (inductance) and contact materials. The behavior of the material is investigated according to the composition, oxide content, and doping agent in silver. As found for low currents, the material transfer direction from the anode to the cathode is maintained at high current and neither opposite transfer direction or bilateral erosion was observed
Optimized multi-wall carbon nanotubes (MWNT) suspensions in aqueous solution have been obtained by joint use of ultrasonification and surfactant. A simple experimental procedure has been established to efficiently evaluate the dependence of the surfactant concentration on the MWNT concentration stable in suspension. The study of 3 different surfactants and MWNT provided by 3 suppliers showed that a threshold surfactant concentration exists above which the MWNT concentration is maximum. Furthermore, it is demonstrated that the maximum MWNT concentration achievable varies from 0.50 to 7.5 g/L depending mainly on quality of the MWNT determined by Raman spectroscopy analysis.
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