An arc forms when the circuit breaker's current-carrying contacts are separated, and it persists for a short period of time after the separation of contacts. This arc is hazardous because of the heat-based energy it produces, which has the potential to explode. The circuit breaker should be able to put out the arc without disrupting the machinery or endangering the people operating it. The phenomena of removing the arc is known as arc extinction.
There are two ways to put out the arc.
1. High resistance method.
2. Low resistance method.
High resistance method for arc extinction.
This approach involves gradually raising the arc resistance over time, which causes the current to decrease until it is too low to sustain the arc. As a result, the current is cut off or the arc is put out. The main drawback is that the arc experiences significant loss. Due to this, it is exclusively utilized in DC circuit breakers and low capacity AC circuit beakers.
Low resistance or current zero method for arc extinction.
This technique is solely used to extinguish arcs in AC circuits. This approach stops the arc from striking even while the voltage across the contacts is rising because the arc resistance is kept low until the current is zero, at which point the arc naturally goes out. This technique for arc extinction is used by all contemporary high power a.c. circuit breakers.
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