Study on dynamic characteristic in force interrupted dc vacuum arc

In this paper, the characteristic of 270 V dc forcing interruption is studied. The experiments are performed on a synthetic test circuit, under 1400 and 2000 A current, with the CuCr electrode vacuum interrupter. With a fixed average current rate, (di/dt) , the arc column shrinks in different situations. In both experiments, the arc diameter changes with three phases. At the beginning of forcing, the arc column seems stable. Consider that the thermal hysteresis plays an important role in it. Then, the arc shrinks with the current decline. Finally, the arc sharply decreases until the arc is quenched. Images of the arc dynamic characteristic are presented.