1. Department of Technical Education Andhra Pradesh
Name : V. Narsimha Reddy
Designation : Lecturer in EEE
Branch : D.E.C.E.
Institute : GMR. Polytechnic Gajwel
Semester : VI Semester
Subject : Electrical Utilization & Automation
Subject Code : EE 605A
Topic : Electric Heating
Duration : 100 Minutes
Sub topic : Electrical Arc Heating
Teaching Aids : PPT, Diagrams, Animation
Revised By : K Chandra Sekhar, L/EEE, GPT, HYD
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2. Recap In this class you have learnt about
Different methods of temperature control of resistance heating
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3. Objectives On completion of this topic, you would be able to know
Arc furnace
Different types of Arc Furnaces
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4. Electric Arc Furnace Production of Electric Arc
The electric supply given to two electrodes is increased and are separated in air from each other
The air gets ionized at high voltage gradient and becomes a good conductor of electricity
Current passes through the air gap in the form of arc.
Once the arc is produced, small voltage is sufficient to maintain it
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5. Electric Arc Furnace Production of Electric Arc
Without high voltage also Arc can be established by short circuit the two electrodes and then withdrawing them apart
The electrodes are made of either carbon or graphite
The temperature of the Arc developed will be around 35000C
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6. Types of electric Arc Furnaces
1. Direct Arc furnace
2. Indirect Arc furnace
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7. Direct Arc Furnace When A.C. supply given to two electrodes.
Two electrode arc furnace
FIG.1
SUPPLY
ELECTRODES
ARC
CHARGE
FURNACE
When A.C. supply given to two electrodes.
Arc is established and current passes through the charges.
Heat is developed due to radiation from Arc.
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8. Direct Arc Furnace The stirring action is
inherent due to electromagnetic force setup by the current
Hence heating of charge
is uniform
3Φ supply is used for
large capacity furnace
The three electrodes are
placed at the three
vertices of an equilateral
triangle
SUPPLY
ELECTRODES
ARC
CHARGE
FURNACE
FIG.1
Two electrode arc furnace
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9. Single Electrode Arc Furnace
FIG.2
One electrode is used.
1Φ supply given between electrode and bottom of furnace.
Arc is developed in between electrode & charge.
It is called single-phase direct Arc furnace or baby Arc
furnace
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10. Direct Arc Furnace Advantages Applications
High temperatures can be produced
More uniform heating of the charge can be obtained
Applications
The most common application of direct arc furnace is to produce steel
Used in R and D
It is used in pilot production plants
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11. Indirect Arc Furnace
Fig.3
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12. Indirect Arc Furnace Fig 3 shows indirect arc furnace
The Arc exists between two electrodes.
Heat developed in the
charge is by the radiation
The temperature of the
charge is lower than
direct Arc furnace
Current does not flow
through charge. Hence
no inherent stirring
action
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13. Indirect Arc Furnace
So, the furnace must be rocked vibrating or tilting by mechanically.
It is called as a rocking Arc furnace also.
The furnace made of cylindered or spherical shape.
Rocking action is operated by an Electric motor
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14. Indirect Arc Furnace Advantages High flexibility High melting
Economical
High efficiency
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15. Indirect Arc Furnace Applications
Indirect arc furnace is used for melting of non-ferrous metals
It can be used in iron foundries where small quantities of iron is required frequently
It is more suitable when the charge is to be varied frequently or heating is intermittent
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16. Summary In this class we have discussed about Arc heating
Different types of electric arc furnaces
Applications of arc furnaces
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17. Quiz 1.Most common application of direct arc furnace is
To produce steel
Melting of non-ferrous metals
Both a & b
None
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18. Quiz 2. Single phase direct arc furnace is also called Boy furnace
Baby furnace
Indirect arc furnace
None
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19. Frequently Asked Questions
What is arc heating?
Explain the construction and working of indirect arc furnace with a sketch
Explain the construction and operation of direct arc furnace with a net sketch
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20. THANK YOU
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