Core Type Furnace Working –
- In core type furnace the core type transformer principle and construction is used.
- It is just like a two winding transformer in a core type furnace and it works on the principle of electromagnetic induction. So, this is called induction heating.
- The transformer in which the charge is to be heated forms the secondary circuit. It is magnetically coupled to the primary by an iron core in a core type furnace.
- When A.C. supply is given to the primary winding, it produces alternating flux.
- These flux are linked with the charge to be heated, producing an emf in it.
- The charge which is to be heated (material) acts as short-circuited secondary winding and causes the flow of eddy current in it. The power loss due to the eddy current in the core produces heat.
Drawbacks Of Core Type Furnace
There are some drawbacks of this furnace, which are given below :
- In the core type furnace, the magnetic coupling between the primary and secondary is very poor. So, it has high leakage reactance and a low power factor. To overcome this difficulty the furnace can be designed for a low frequency such as 10 Hz.
- The size of the crucible is of odd shape and convenient from the metallurgical point of view.
- If a normal frequency supply is employed for the operation of such furnaces, the electromagnetic forces cause severe stirring action in the molten metal.
- If the current density exceeds 5 A/mm2, the pinch effect (formation of bubbles and voids, etc. ) due to electromagnetic forces may cause interruption of the secondary circuit.
- The furnace cannot work if the secondary is not closed. Since no induction principle is completed there so, a charge of the molten metal always poured in the crucible. So, continuous.
- Such furnaces are not suitable for intermittent services.
Advantages Of Core Type Furnance
- Absence of crucible in core type furnace.
- Core type furnace having a high power factor 0.8 to 0.85 comparatively.
- A uniform stirring of charge gives the homogeneous composition.
- Ideal working condition in a cool atmosphere with no dirt, noise, or smoke.
- Control is simple.
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