SF circuit breakers use the puffer principle with SF6 gas.
This methods cools and extinguishes the electrical arc as it passes through zero current by puffing a gas compressed by a piston attached to the moving contact. The gas is channeled by an insulating nozzle towards the tubular arcing contacts that are used as an exhaust.
The operating sequence in a puffer-type breaking chamber with the moving part actuated by a control mechanism is as follows:
1- The circuit breaker is closed.
2- Following an opening order the main contacts separate (a) and the current is directed into the breaking circuit (b).
When the main contacts start to open the piston (c) slightly compresses the SF6 gas in the compression chamber (d)
3- An electrical arc appears on separation of the arcing contacts. The piston (c) continues its travel downwards.
A small quantity of the gas channeled by the insulating nozzle (e) is injected towards the arc.
For low current breaking, the arc is cooled by forced ventilation. However, for high currents the thermal expansion moves the hot gases towards cooler parts in the breaking unit.
The distance between arcing contacts becomes sufficient to allow breaking of the current when it passes through zero due to the dielectric properties of the SF6 gas
4 The moving parts finish their movement and injection of cold gas continues until the contacts are fully open.
he circuit breaker is open
This methods cools and extinguishes the electrical arc as it passes through zero current by puffing a gas compressed by a piston attached to the moving contact. The gas is channeled by an insulating nozzle towards the tubular arcing contacts that are used as an exhaust.
The operating sequence in a puffer-type breaking chamber with the moving part actuated by a control mechanism is as follows:
1- The circuit breaker is closed.
2- Following an opening order the main contacts separate (a) and the current is directed into the breaking circuit (b).
When the main contacts start to open the piston (c) slightly compresses the SF6 gas in the compression chamber (d)
3- An electrical arc appears on separation of the arcing contacts. The piston (c) continues its travel downwards.
A small quantity of the gas channeled by the insulating nozzle (e) is injected towards the arc.
For low current breaking, the arc is cooled by forced ventilation. However, for high currents the thermal expansion moves the hot gases towards cooler parts in the breaking unit.
The distance between arcing contacts becomes sufficient to allow breaking of the current when it passes through zero due to the dielectric properties of the SF6 gas
4 The moving parts finish their movement and injection of cold gas continues until the contacts are fully open.
he circuit breaker is open
Released for:Schneider Electric Nigeria
