Experimental investigation of influence of a contact separation time on the breaking capacity of a vacuum circuit breaker

In the present work, influence of the beginning of the contact opening of the vacuum circuit breaker on the main characteristics of the discharge and the breaking capacity of the breaker is studied. In the experiment, Cu-Cr bulk electrodes with a diameter of twenty millimeters were used. Synthetic circuit generated a half-sinusoidal current with duration of 10 ms and amplitude of 10 kA, followed by the transient recovery voltage with amplitude of 30 kV. The velocity of a movable electrode was close to 1.35 m/s. In the experiment, only the beginning of movement of electrode was changeable. All other parameters were fixed. Traces of arc voltage, post-arc current, Langmuir probe current, as well as images of the arcing gap were recorded and analyzed. The earlier electrode starts moving, the longer both time interval at arc operation and interelectrode gap distance during the arc. With this, radial contraction of the arc column is amplified, arc voltage increases, thermal energy dissipated in the anode increases also, and the breaking capacity goes down.