Experimental study on relationship between bridge and arc phenomena in breaking Ag contacts

An experimental study on the relationship between bridge and arc phenomena in breaking Ag contacts has been carried out. The circuit current condition was changed to control the transition ratio to the gaseous phase. The bridge voltage waveform, the arc duration and the contact resistance of breaking contact were measured. According to past works, the bridge voltage at the moment of the rupture of bridge is 0.74 V for Ag contacts. The voltage of experimental result in this study was grouped into three levels; approximately 0.3, 0.4 and 0.8 V, and the distribution shifted to lower group as the transition ratio to the gaseous phase increases. When the arc duration was short and the transition ratio was almost zero, the voltage was 0.8 or 0.4 V. The voltage became 0.3 V in the case when the arc always transited to the gaseous phase and the transition ratio was 1. The bridge voltage waveform changed during 2 or 3 operations after the change of types of arc, and the tendency of change was similar to that of contact resistance.