PROJECT TITLE :

Resistance increase of vacuum interrupters due to high-current interruptions

ABSTRACT:

The resistance of vacuum interrupters will be calculated from the geometry and resistivity of current carrying parts and the additional resistance of the contact points between movable and fastened contacts. Since vacuum interrupter contacts are designed as flat contacts facing every alternative, the resistance is mainly determined by contact force, hardness and resistivity of the contact material. It's known that the contact material changes consistency and structure during short-circuit interruptions among melting depth. Indeed, the overall resistance of a vacuum interrupter has been observed to extend by up to sixtyp.c once short-circuit creating and breaking tests. Since the resistance increase across the switching device is taken into account by IEC and IEEE standards collectively of the acceptance criteria for the integrity of the interrupter when tests, it's essential to perceive the origin of this increase. Completely different causes are mentioned, among them the change of grain structure, resistivity and hardness of the molten high layer of the contact, and flatness of the contact surface. An increase of hardness and a different position of contact points seem to be the main factors accountable for the increased resistance.