A measurement and a classification of arcing phenomena of AgPd alloy contacts in low pressure

To understand the arcing phenomena observed when contact is breaking, an apparatus was developed to observe and record arc voltage waveforms. The apparatus is formed by adding a waveform acquisition circuit composed of an A/D converter, memories and control circuits to the conventional contact measurement system. Using this equipment, the voltage waveforms were observed for Ag, Pd or their alloys contacts for 500 operations under various surrounding ambient pressures. The waveforms were analyzed with respect to length, slope and fluctuation. The waveform tendencies were classified by the combination of ambient pressure and alloy ratio. For example, when the Ag content is high or the ambient pressure is high, the transition to gaseous phase becomes smoother with the increase of operation repetitions. When the Pd content increases and the ambient pressure is low, only a short metallic phase arc occurs. Using the measurement and classification, data for establishing the relationship between the ambient pressure and the contact material was acquired. The classification carried out by using contact resistance was similar to that by arc waveforms.