Transcript Arc Furnaces

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
Revised By
:
:
PPT, Diagrams, Animation
K Chandra Sekhar, L/EEE, GPT, HYD
9EE605A.15to16
1
Recap
In this class you have learnt about
• Different methods of temperature control of resistance
heating
9EE605A.15to16
2
Objectives
On completion of this topic, you would be able to know
• Arc furnace
• Different types of Arc Furnaces
9EE605A.15to16
3
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
9EE605A.15to16
4
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
9EE605A.15to16
5
Types of electric Arc Furnaces
1. Direct Arc furnace
2. Indirect Arc furnace
9EE605A.15to16
6
Direct Arc Furnace
SUPPLY
ELECTRODES
ARC
CHARGE
FURNACE
FIG.1
Two electrode arc 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.
9EE605A.15to16
7
Direct Arc Furnace
• The stirring action is
inherent due to
SUPPLY
electromagnetic force
setup by the current
ELECTRODES
• Hence heating of charge
is uniform
• 3Φ supply is used for
ARC
large capacity furnace CHARGE
• The three electrodes are FURNACE
placed at the three
vertices of an equilateral
triangle
9EE605A.15to16
FIG.1
Two electrode arc
furnace
8
Single Electrode Arc Furnace
1Φ AC
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
9EE605A.15to16
9
Direct Arc Furnace
Advantages
• 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
9EE605A.15to16
10
Indirect Arc Furnace
Fig.3
9EE605A.15to16
11
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
9EE605A.15to16
12
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
9EE605A.15to16
13
Indirect Arc Furnace
Advantages
• High flexibility
• High melting
• Economical
• High efficiency
9EE605A.15to16
14
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
9EE605A.15to16
15
Summary
In this class we have discussed about
• Arc heating
• Different types of electric arc furnaces
• Applications of arc furnaces
9EE605A.15to16
16
Quiz
1.Most common application of direct arc furnace is
a. To produce steel
b. Melting of non-ferrous metals
c. Both a & b
d. None
9EE605A.15to16
17
Quiz
2. Single phase direct arc furnace is also called
a.
Boy furnace
b.
Baby furnace
c.
Indirect arc furnace
d.
None
9EE605A.15to16
18
Frequently Asked Questions
1) What is arc heating?
2) Explain the construction and working of indirect arc furnace
with a sketch
3) Explain the construction and operation of direct arc furnace
with a net sketch
9EE605A.15to16
19
THANK YOU
9EE605A.15to16
20