Transcript Advantages of Dielectric heating

DIELECTRIC HEATING
Mr. Vijay Balu Raskar - Electrical Engineer
When a solid dielectric material
(Insulating) is subjected to an
alternating electric field , it is not
supposed to carry any current.
However, in practice some leakage
current passes through it and power
loss is takes place. This loss is called as
dielectric loss and result into heating
of dielectric material.
Mr. Vijay Balu Raskar - Electrical Engineer
APPLICATION OF DIELECTRIC
HEATING
 Plywood Industry
 Sand Core Baking
 Plastic Industry
 Tobacco Industry
 Bakeries
 Electronic Sawing
 Dehydration of food
 Electro medical application
 Book Binding
Mr. Vijay Balu Raskar - Electrical Engineer
Advantages of Dielectric heating
1) Heating is very quick
2) The efficiency is higher
3) Heating is uniform
4) Being free from smoke, dust,
process is very clean
5) There are no flue gases, no risk of
pollution
6) Heat is produced due to dielectric
loss occurs in the material itself
Mr. Vijay Balu Raskar - Electrical Engineer
ARC HEATING
• One of the popular method of heating.
• Principle:- When voltage is applied between the
two electrodes separated by small distance in air is
increased, a stage is reached when the air gets
ionized and air act like conducting. Hence, current
flows between the electrodes in the form of
continuous spark called ARC. This self sustained
discharge of electricity between 2 electrodes
through air is known as “Electric ARC”.
Mr. Vijay Balu Raskar - Electrical Engineer
An ARC drawn between 2 electrodes
has a temperature between 3000 C to
3500 C depending upon the electrode
material.
ARC Heating Types:1) Direct ARC heating
2) Indirect ARC heating
Mr. Vijay Balu Raskar - Electrical Engineer
Direct ARC Furnance
Mr. Vijay Balu Raskar - Electrical Engineer
Direct ARC :ARC is established between the charge and
the electrode.
The heat is directly conducted to the
charge which charge absorb.
Hence, this method is called Direct ARC
heating.
This consist of Carbon or Graphite
electrode.
The power is controlled by adjusting the
ARC length by moving the electrodes
manually or automatically.
Mr. Vijay Balu Raskar - Electrical Engineer
USE (Direct ARC)
1) Making of Alloy steels like stainless
and high speed steel
2) Composition can be controlled
during refining process.
Direct ARC operates at 0.8 p.f. Lagging
Mr. Vijay Balu Raskar - Electrical Engineer
INDIRECT ARC:
Mr. Vijay Balu Raskar - Electrical Engineer
INDIRECT ARC:
ARC is formed between two electrodes
and heat is transmitted to the charge
by radiation.
Lower temperature than direct ARC.
It Operates at 0.85 p.f. lagging
have to provide rocking motion
through a motor to distribute heat
uniformly.
USE:- melting non-ferrous metals.
Mr. Vijay Balu Raskar - Electrical Engineer
Due to application of sufficiently high voltage across an
air gap causes the air in the gap to get ionized and form
ARC
ARC drawn between two electrodes develop high
temperature (3000-3500°C)depending upon material
ARC may be used in following ways:
by striking between charge and electrodesprinciple behind Direct ARC Furnace
by striking between two electrodes
principle behind Indirect ARC Furnace
by striking between an electrode and the
two metallic pieces to be joined principle behind ARC welding
Mr. Vijay Balu Raskar - Electrical Engineer
Principle of transformers
In the transformer, supply is utilized by secondary.
Mr. Vijay Balu Raskar - Electrical Engineer
•Induction method is based on Principle of “Electromagnetic
Induction”
•When alternating Current flows in a conductor it produces
alternating flux.
•If any other conducting material is placed in this magnetic flux
emf gets induced in it
•This induced emf drives eddy current in that piece and power
loss due to eddy currentMr. appears
heat.
Vijay Balu Raskar as
- Electrical
Engineer
Factors for Induction heating:1) it is proportional to relative
permeability. Heating produced in
magnetic material is more than non
magnetic material.
2) Heating is proportional to MMF.
Force can be vary by changing current
or number of turns.
3) Heating effect can be increased by
employing high frequency supply.
Mr. Vijay Balu Raskar - Electrical Engineer
DIRECT INDUCTION HEATING
In this, currents are induced in the charge itself. This is usually used
in furnaces for melting (extraction of metal from ore), melting of
metals etc.
This requires very high frequency supply.
They are classified as core and coreless type induction furnaces.
Mr. Vijay Balu Raskar - Electrical Engineer
INDIRECT INDUCTION HEATING
(Example :- Oven)
In this, eddy currents are induced in the heating element.
Thus heat produced by heating element is then transferred to
the charge by radiation or convection.
Mr. Vijay Balu Raskar - Electrical Engineer
Advantages:1) Simple and foolproof method of temperature control
2) No external temperature control equipments required
Limitations:1) Poor Power factor
2) Complicated Construction
Applications:It is used for general heat treatment of metallic and other charges.
Mr. Vijay Balu Raskar - Electrical Engineer
Mr. Vijay Balu Raskar - Electrical Engineer