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Which medium used to extinction of arc in air circuit breaker
Air
SF6
Oil
None of above
Air
Quick Summary: An Air Circuit Breaker (ACB) uses atmospheric air at normal pressure as the arc quenching medium. When the contacts separate, the arc is stretched and cooled by the surrounding air to ensure extinction.
An Air Circuit Breaker (ACB) uses atmospheric air at normal pressure as the arc quenching medium. When the contacts separate, the arc is stretched and cooled by the surrounding air to ensure extinction.
Varc=I×Rarc — Arc voltage is proportional to arc resistance and current
Rarc=Aρ×l — Arc resistance depends on resistivity, length, and cross-sectional area
As the ACB contacts move apart, an arc is formed between them. The arc is then forced into an arc chute containing metal plates (splitter plates), which divide the arc into several smaller arcs in series. This increases the arc resistance and effectively cools the arc, causing the voltage drop across the arc to exceed the supply voltage, leading to extinction.
ACBs are typically used for low voltage systems (up to 1 kV).
The arc chute provides a long path for the arc to cool down and increase its resistance.
Air is cost-effective, readily available, and safe for low voltage applications.
Simple design and construction
Easy maintenance and inspection
No risk of fire or oil-related hazards
Larger size compared to SF6 or Vacuum circuit breakers
Not suitable for very high-voltage operations
Sensitive to atmospheric humidity and pollution
Industrial power distribution systems
Low voltage switchgear panels
Motor control centers
SF6 is typically used for high and medium voltage applications due to its high dielectric strength.
Oil circuit breakers were common in historical systems but have been replaced due to the risk of oil fires.
A is correct — Air is the primary medium used for arc extinction in an Air Circuit Breaker.
Remember: For high voltage, SF6 is preferred due to high electronegativity; for low voltage, air is preferred due to its simplicity and economic efficiency.