This FAQ has been written for NEAL (North East Africa and Levant) region. If you are looking for information for another region, please select the correct country from the top-left dropdown in the page and 'Navigate to Browse FAQs' in the Support menu.
LF circuit breakers use the SF6 gas self expansion technique.
This technique is the result of many years’ experience in SF6 technology and major research work.
It combines the effect of thermal expansion with a rotating arc to create arc blowing and quenching conditions.
The result is reduced control energy requirements and arcing contact erosion; this increases mechanical and electrical endurance.
The operating sequence of a self-expansion breaking chamber, whose moving part is driven by the mechanical operating mechanism, is as follows:
1-The circuit breaker is closed
2-On opening of the main contacts (a) the current is shunted into the breaking circuit (b).
3- On separation of the arcing contacts, an electrical arc appears in the expansion volume (c).
The arc rotates under the effect of the magnetic field created by the coil (d) through which flows the current to be broken:
□ the overpressure created by the temperature build-up of the gas in the expansion volume (c ) causes a gaseous flow blowing the arc inside the tubular arcing contact (e)
□ resulting in arc quenching when the current passes through the zero point.
4- The circuit breaker is open.
This technique is the result of many years’ experience in SF6 technology and major research work.
It combines the effect of thermal expansion with a rotating arc to create arc blowing and quenching conditions.
The result is reduced control energy requirements and arcing contact erosion; this increases mechanical and electrical endurance.
The operating sequence of a self-expansion breaking chamber, whose moving part is driven by the mechanical operating mechanism, is as follows:
1-The circuit breaker is closed
2-On opening of the main contacts (a) the current is shunted into the breaking circuit (b).
3- On separation of the arcing contacts, an electrical arc appears in the expansion volume (c).
The arc rotates under the effect of the magnetic field created by the coil (d) through which flows the current to be broken:
□ the overpressure created by the temperature build-up of the gas in the expansion volume (c ) causes a gaseous flow blowing the arc inside the tubular arcing contact (e)
□ resulting in arc quenching when the current passes through the zero point.
4- The circuit breaker is open.
Released for: Schneider Electric Egypt and North East Africa
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