Experimental Investigation of Vacuum Arc Behavior under Different Contacts in Vacuum Interrupters

Vacuum interrupter is widely used in the medium voltages. Controlling the arc by the magnetic field is effective method to improve the breaking capacity. The TMF forces the constricted arc to rotate to reduce local overheating. In this paper, three TMF contacts, which are Swastika, cup-shaped and double TMF contacts, are investigated in a demountable vacuum chamber with a high-speed camera. The arc voltage and current are also recorded. The experiments were conducted with circuit currents from 5kA to 20 kA (rms) with a frequency of 50 Hz. It was observed that the arc of Swastika and double TMF contacts rotated under high current. The arc speed of double TMF contacts is higher than that of Swastika contacts. The cup-shaped contacts have a higher arc voltage and noise compared with the other two. The Swastika contacts were burned the most serious.