Abstract: A three-phase circuit breaker with self-extinguishing expansion and rotating arc structures comprises an arc extinguishing chamber per pole and housing a pair of contacts, one stationary and one moveable, a coil to rotate the arc, and an exhaust channel in at least one contact to provide an opening a communication and gas outflow between the extinguishing chamber and the expansion volume of an enclosure filled with SF6. The extinguishing chamber has a square or rectangular cross-section to resorb the gas plug after braking of the gas rotation movement, and improve stirring of the gas in the extinguishing chamber.

Abstract: An inside of tubular contacts of a self-extinguishing expansion SF.sub.6 -gas circuit breaker including guiding ribs arranged to oppose any vortex-effect swirling gas flow between a first extinguishing chamber and a second expansion chamber. The presence of these ribs improves the dielectric withstand of the circuit breaker, and prevents any arc restriking inside the contacts.