The invention relates to a switching device which has two stationary contacts and a movable contact in a switching chamber. The stationary contacts are arranged next to each other along a longitudinal direction, and the switching chamber has a switching chamber wall with opposing transversal lateral wall parts and opposing longitudinal lateral wall parts. Each of the two stationary contacts is arranged at a distance to one of the transversal lateral wall parts, said distance being shorter than the respective distance to the longitudinal lateral wall parts.

Disclosed are an arc extinguishing unit, a circuit breaking unit, and an air circuit breaker including the same. The present disclosure provides an arc extinguishing unit, a circuit breaking unit, and an air circuit breaker, including: side plates spaced apart from each other and disposed to face each other; a plurality of grids disposed between the side plates, spaced apart from each other, and coupled to the side plates, respectively; and a grid cover located above the grid and covering the grid, wherein the grid includes a grid leg extending downward to surround from both sides a protruding contact disposed to extend upward from a movable contact; and a first protective part formed to surround at least a portion of the grid leg at a lower portion of the grid leg.

An electric circuit breaker device includes: an igniter provided to a housing; a projectile disposed in an accommodating space formed in the housing, the projectile being to be projected along the accommodating space by energy received from the igniter; a conductor piece that is provided to the housing, forms a portion of an electric circuit, includes in a portion thereof a cutoff portion to be cut off by the projectile, and is disposed with the cutoff portion crossing the accommodating space; an arc-extinguishing region positioned on a side opposite to the projectile prior to actuation of the igniter with the cutoff portion interposed between the arc-extinguishing region and the projectile, and configured to receive the cutoff portion cut off by the projectile; a first coolant material disposed in the arc-extinguishing region; and a second coolant material disposed between the projectile and the cutoff portion in the accommodating space prior to actuation of the igniter.