Voltage fluctuation of short-time arc at slowly separating silver-based contacts

Arc discharge at breaking electrical contact is considered as a main source of an undesired electromagnetic (EM) noise. Short-duration time arc before an ignition of the continuous metallic arc discharge arises and causes high frequency EM noise. To clarify the characteristics and the mechanism of the generation of EM noise, the fluctuation of voltage and duration of short-time arc at slowly separating silver-based contacts are investigated experimentally in this paper. The opening velocity of the moving electrode was 60 μm/s and it was determined so that it satisfied quasi-thermal equilibrium condition. Ag and Ag_88.3wt%SnO_211.7wt% were chosen as contact test material. Breaking waveforms and aspects are measured. The voltage fluctuation for the Ag material case is larger than that for the Ag _88.3wt%SnO_211.7wt%. For the Ag material case, some short-duration time arcs before the ignition of the continuous metallic arc discharge are observed. The arc duration of the continuous metallic arc at the first operation is relatively short. The measured aspects by high-speed camera indicate that the locations of the short-time arc are changed by each short-time arc. As operation numbers increase, arc duration becomes longer rapidly. The measured aspects by the high-speed camera indicated that the locations of the short-time arc are changed by each short-time arc and melting region on the contact surface due to the short-time arcs is enlarged dramatically by the short-time arc. These results are basic and useful finding and consideration to clarify not only the correspondence to noise generation of the contact-breaking phenomena but the material dependency for EMC problems.