Current Chopping Introduced by Arc Collapse

The intensive cooling by a moving gas can cause violent elongations and curls of the circuit breaker arc, especially when small currents are interrupted. During the elongation the arc voltage increases rapidly. This introduces a breakdown across a smaller distance by short circuiting a part of the arc. Such a breakdown is called here arc colapse. The abrupt decrease in resistance and arc voltage may give rise to an oscillating discharge of the circuit breaker parallel capacitance into the arc path. This oscillation can force the main current to zero and thus cause current chopping. In this paper this kind of current chopping is studied and compared with chopping by instability oscillation. It is theoretically explained why these independent origins for chopping produce the same chopping levels.