Effects of switching speed on arcing and contact erosions in residential circuit breakers

Inhalt:
Contact erosions are critical for performance of circuit breakers. It has been generally accepted that switching the contacts open with fast speed helps reducing the arcing, and hence reducing the contact erosions. However, some observations during repetitive, low current switching have shown contradictory results. An analytical study to arc power during contact opening in residential circuit breakers is performed in this paper. It is found that opening speed of contacts has opposite effects on arc power, depending on the impedance of the circuit. At high current, low impedance, fast opening results in lower arc power, while at low current, high impedance, slow opening results in lower arc power. Experiments are performed to verify the results of the analytical study. Arc power, contact erosions and high speed videos are compared between high switching speed and low switching speed at low current conditions. At high current conditions, arc power is compared with different delay time and different circuit impedance with a fixed opening speed. The experiment results agree with the analytical study.