Mr. Vijay Balu Raskar - Electrical Engineer DIELECTRIC HEATING Mr. Vijay Balu Raskar - Electrical Engineer

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

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

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

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

Mr. Vijay Balu Raskar - Electrical Engineer Direct ARC Furnance Mr. Vijay Balu Raskar - Electrical Engineer

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

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

Mr. Vijay Balu Raskar - Electrical Engineer INDIRECT ARC: Mr. Vijay Balu Raskar - Electrical Engineer

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

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 forms 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 electrodes-principle 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

Mr. Vijay Balu Raskar - Electrical Engineer Principle of transformers In the transformer, supply is utilized by secondary. Mr. Vijay Balu Raskar - Electrical Engineer

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 current appears as heat. Mr. Vijay Balu Raskar - Electrical Engineer

Mr. Vijay Balu Raskar - 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:- Limitations:- Applications:- Simple and foolproof method of temperature control No external temperature control equipments required Poor Power factor Complicated Construction It is used for general heat treatment of metallic and other charges. Mr. Vijay Balu Raskar - Electrical Engineer

Mr. Vijay Balu Raskar - Electrical Engineer