Spectroscopic measurement of Ag break arc

The authors have studied the maintaining mechanism of the contact arc discharge. For this object, a spectroscopic measurement system was composed using two monochromators and a bifurcated image fiber. Arc voltage waveform, arc current waveform, Ag II (243.78 nm) spectrum intensity, and Ag I (328.07 nm) spectrum intensity are measured for an Ag break arc, under the conditions where source voltage E=6/spl sim/48 V, load inductance L=0-2.3 mH, and closed contact current I/sub 0/=0.6/spl sim/6A. The spectrum intensity of Ag II (ion line) becomes a maximum value near the gaseous phase transition point, and it gradually decreases in the gaseous phase. The spectrum intensity of Ag I (excited atom line) increases until the gaseous phase transition point. After the gaseous phase transition, Ag I becomes a constant value (40/spl sim/50) which does not depend on the circuit condition. Furthermore, in the boundary closed current at which the transition ratio is 50%, it is clarified that the average spectrum intensity of Ag II has a constant value without depending on the circuit condition. Therefore, the transition to gaseous phase is made when the mean number of Ag ions exceeds a certain value.