Experimental Study on Arcing Process and Contact Erosion under Transverse Magnetic Field

Arc characteristics and contact erosion of Ag, AgNi and Ag/SnO2 contacts were studied when the opening arcs were driven by transverse magnetic field. The experiments were carried out with a DC 28V/10A pure resistive load. The opening velocity varies from 10 mm/s to 50 mm/s. The transverse magnetic fields are provided by magnets and their flux density on the contact axes varies from 0 to 200 mT. The experiments were conducted in a hermetic chamber filled with pure nitrogen. Time variations of arc images were recorded by using a high speed camera. Relationships between flux density and arc parameters, such as arc durations, 2-dimensional distribution of arc positions and arc velocities, were obtained for those contacts. Contact erosion was observed and material transfer mass was measured after breaking operations. Decline ratio of the arc durations and alleviation of the mass transfer by the magnetic field no longer increase with the increment of the flux density, so the critical flux density for each contact material were finally obtained. The results can be used to design magnetic blow contacts in hermetic relays.