The electrical energy is utilized to produce the electric arc in the air.
When an electric current is passed through the two electrodes at very high voltage, then air as a media between them gets ionized and the current flows through the air which is known as an arc.
The heat is generated, this heat is used to melt the material.
A very high voltage is required to generate the arc, but small voltage is sufficient to maintain the arc.
In arc furnaces, the arc is produced by short-circuiting the two electrodes momentarily and withdrawing the back. Thus, high voltage is not required to start the arc.
Temperature obtained by these type electric arc are 1000°C and 3500°C depending upon the electrodes used.
Methods of striking the arc
There are two methods of string the arc :
(i) H.T. strike. (ii) L.T. strike.
In this method a constant air gap is maintained between two electrodes which are connected to secondary of a step-up transformer.
By gradually increasing the primary voltage with the help of potential divider, arc is made to struck between the electrodes.
The arc is struck when there is sufficient voltage across the electrodes. Then the air gets ionised in the air gap between them.
In this method, the electrodes are connected across L. V. side of transformer.
First they arc shorted and then immediately separated resulting in production of arc.
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