Bouncing phenomena of vacuum interrupters

Bouncing is a phenomenon often observed during circuit-breakers operation. The effect occurs at the moment, when the interrupter contacts touch during closing. For vacuum interrupters, bouncing is caused by the oscillatory motion of the movable vacuum interrupter stem in conjunction with the associated contact springs. The dependencies between involved masses, springs and speeds regulate the bouncing period. In addition, the motion of the kinematic chain of the breaker mechanism has to be considered. A careful evaluation of bouncing periods and durations measured on a variety of breakers revealed a correlation of the bouncing duration with a resonance of the bouncing frequency of the vacuum interrupter and the oscillatory frequency of the kinematic chain. The impact of bouncing on the capability of short-circuit making and on capacitive switching is discussed with the conclusion that it is negligible for the performance of the vacuum interrupter.