Are erosion behaviour of silver electric contacts in a single are discharge across a static gap

Static-gap electrical erosion experiments are conducted using an iron needle cathode and silver anode, where the gap distance can be adjusted with high precision and high accuracy. The effects of supply voltage and gap distance on the are erosion behaviour are investigated in a single are discharge. Results show that the air breakdown occurs at 70V/mum up to 175V, at 330V at 10 mum, and 500V at 40 mum. Since the gap distance increases with increasing are duration, the residual voltage is always positive at a smaller gap distance with lower supply voltage. However, a negative residual voltage occurs at a larger supply voltage. This negative residual voltage is caused by positive metallic ions accumulated on the cathode. The particle sputtering-deposition model can reasonably explain this negative residual voltage. With increasing gap distance, the erosion area increases and reaches a maximum. However, it diminishes at higher supply voltages due to the increased amount of gaseous phase are. It is seen from the eroded anode surface that the metallic phase are mainly causes the crater with many strip-like metallic particles, but the gaseous phase are significantly results in a lot. of silver powder.