CONTINUATION OF PART -1 OF CIRCUIT BREAKER
Today we are going to discuss about arc extension and methods of arc extension of a circuit breaker
Electrical Arc – An electric arc or arc discharge is an electrical breakdown of a gas that produces a prolonged electrical discharge. The current through a normally non-conductive medium such as air produces a plasma, which can produce visible light.
Arc extension or arc quenching
At the point when the current conveying contacts of the electrical switches are moved separated, then an arc is formed, which demand for a short period after the partition of contacts. This circular segment is dangerous because of the energy created in it as heat which may bring about explosive force.
The circuit breaker should be capable of extinguishing the arc without causing any damage to the equipments or danger to any person. In this case the arc plays an important role in the behaviour of the circuit breaker. The interference of DC arc is generally more troublesome than the arc produces by an AC arc. In an AC arc as the current becomes zero during the normal wave, then the arc disappears and it is suspended from restriking.
The conductances of the arc is relative to the quantity of electrons per cubic centimeter created by the ionisation, the square of the diameter across of the circular segment and the crossponding of the length. It is consequently important to lessen the thickness or the density of the free electrons, i.e diminishes the ionisation and decline or decreases the diameter across the arc.
Methods of arc extension
Basically there are two types of methods of arc extension are as follows :-
1)High resistance method
2)Low resistance method or zero current interruption method
High resistance method –
In this technique the arc is contolled in such a way that it’s effective resistance increase with the time, so that the current is reduced to such a value that heat formed by it is not sufficient to maintain the arc or thus arc is extinguished.
Because of the resistive nature of the arc discharge, most of the energy in the system will be dissipated within the circuit breaker. This is the main drawback of this technique.
The following are the reasons which can increase the resistance of the arc :-
1)Cooling of arc
2)Increasing the length of the arc
3)Reducing the cross-section of the arc
4)Splitting of arc
Low resistance method or zero current interruption method –
This method is applicable only in AC circuit interruption because there are natural zero of the current, 100 times in a second for 50Hz three phase supply system. This is quite possibly the main focal points of AC circuit for the arc interruption purpose because the current is not allowed to rise again.
In this strategy the arc resistance is kept low until the current is zero where the arc itself extinguishes naturally and it’s kept from restriking after it has gone out at a specific.
Read part-1 of all about circuit breaker from the link below https://discoverknowledge49.blogspot.com/2020/10/all-about-circuit-breaker.html
THE REST WILL BE CONTINUE IN THE NEXT BLOG SO KEEP READING
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