ARC EXTINCTION
It is essential that arc should be extinguished as early as possible . There are two methods of extinguishing the arc in circuit breakers which are namely
1. High resistance method
2. low resistance method or current zero method
1.High resistance method:-
In high resistance method the arc resistance is increased with time. This will reduce the current to such a value which will be insufficient to maintain the arc. thus the current is interrupted and the arc is extinguished. This method is employed in only d.c. circuit breakers. The resistance of the arc may be increased by lengthening the arc, cooling the arc, reducing the cross section of the arc and splitting the arc .
Low resistance method:-
The low resistance or current zero method is employed for arc extinction in a.c. circuits. In this method arc resistance is kept low unit current zero where extinction of arc takes place naturally and is prevented from restriking . This method is employed in many of the modern a.c. circuit breakers.
2. low resistance method or current zero method
1.High resistance method:-
In high resistance method the arc resistance is increased with time. This will reduce the current to such a value which will be insufficient to maintain the arc. thus the current is interrupted and the arc is extinguished. This method is employed in only d.c. circuit breakers. The resistance of the arc may be increased by lengthening the arc, cooling the arc, reducing the cross section of the arc and splitting the arc .
Low resistance method:-
The low resistance or current zero method is employed for arc extinction in a.c. circuits. In this method arc resistance is kept low unit current zero where extinction of arc takes place naturally and is prevented from restriking . This method is employed in many of the modern a.c. circuit breakers.
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