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  • 1. DIELECTRIC HEATING Mr. Vijay Balu Raskar - Electrical Engineer
  • 2. Wasted energy appears as heat calleddielectric loss.The non metallic material with poorthermal conductivity can be veryeffectively heated by dielectricheating.Dielectric loss is proportional tofrequency and square of the supplyvoltage.Frequency can be selected between 10to 30kHz and voltage about 20kV. Mr. Vijay Balu Raskar - Electrical Engineer
  • 3. When a solid dielectric material(Insulating) is subjected to analternating electric field , it is notsupposed to carry any current.However, in practice some leakagecurrent passes through it and powerloss is takes place. This loss is called asdielectric loss and result into heatingof dielectric material. Mr. Vijay Balu Raskar - Electrical Engineer
  • 4. 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
  • 5. Advantages of Dielectric heating1) Heating is very quick2) The efficiency is higher3) Heating is uniform4) Being free from smoke, dust,process is very clean5) There are no flue gases, no risk ofpollution6) Heat is produced due to dielectricloss occurs in the material itself Mr. Vijay Balu Raskar - Electrical Engineer
  • 6. 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
  • 7. An ARC drawn between 2 electrodeshas a temperature between 3000 C to3500 C depending upon the electrode material. ARC Heating Types:- 1) Direct ARC heating 2) Indirect ARC heating Mr. Vijay Balu Raskar - Electrical Engineer
  • 8. Direct ARC Furnance Mr. Vijay Balu Raskar - Electrical Engineer
  • 9. Direct ARC :-ARC is established between the charge andthe electrode.The heat is directly conducted to thecharge which charge absorb.Hence, this method is called Direct ARCheating.This consist of Carbon or Graphiteelectrode.The power is controlled by adjusting theARC length by moving the electrodesmanually or automatically. Mr. Vijay Balu Raskar - Electrical Engineer
  • 10. 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
  • 11. INDIRECT ARC: Mr. Vijay Balu Raskar - Electrical Engineer
  • 12. INDIRECT ARC:ARC is formed between two electrodesand heat is transmitted to the chargeby radiation.Lower temperature than direct ARC.It Operates at 0.85 p.f. lagginghave to provide rocking motionthrough a motor to distribute heatuniformly.USE:- melting non-ferrous metals. Mr. Vijay Balu Raskar - Electrical Engineer
  • 13. Due to application of sufficiently high voltage across anair gap causes the air in the gap to get ionized and formARCARC drawn between two electrodes develop hightemperature (3000-3500°C)depending upon materialARC may be used in following ways:by striking between charge and electrodes-principle behind Direct ARC Furnaceby striking between two electrodesprinciple behind Indirect ARC Furnaceby striking between an electrode and thetwo metallic pieces to be joined -principle behind ARC welding Mr. Vijay Balu Raskar - Electrical Engineer
  • 14. SUBMERGED ARC FURNACE Mr. Vijay Balu Raskar - Electrical Engineer
  • 15. ARC is formed between carbon electrodesplaced at top and earth electrode or theconducting earth itself.Number of electrodes depends on type ofsupply.Power is controlled by varying supply or varyingdistance between electrodes.Better mixing of Charge.P.f. is 0.8 LaggingUSE:-Manufacturing of ferro-chrome and ferro-manganese Mr. Vijay Balu Raskar - Electrical Engineer
  • 16. Principle of transformersIn the transformer, supply is utilized by secondary. Mr. Vijay Balu Raskar - Electrical Engineer
  • 17. •Induction method is based on Principle of “ElectromagneticInduction”•When alternating Current flows in a conductor it producesalternating flux.•If any other conducting material is placed in this magnetic fluxemf gets induced in it•This induced emf drives eddy current in that piece and powerloss due to eddy current appears as heat. Mr. Vijay Balu Raskar - Electrical Engineer
  • 18. Factors for Induction heating:-1) it is proportional to relativepermeability. Heating produced inmagnetic material is more than nonmagnetic material.2) Heating is proportional to MMF.Force can be vary by changing currentor number of turns.3) Heating effect can be increased byemploying high frequency supply. Mr. Vijay Balu Raskar - Electrical Engineer
  • 19. DIRECT INDUCTION HEATINGIn this, currents are induced in the charge itself. This is usually usedin furnaces for smelting (extraction of metal from ore), melting ofmetals etc.This requires very high frequency supply.They are classified as core and coreless type induction furnaces. Mr. Vijay Balu Raskar - Electrical Engineer
  • 20. INDIRECT INDUCTION HEATING (Example :- Oven)In this, eddy currents are induced in the heating element.Thus heat produced by heating element is then transferred tothe charge by radiation or convection. Mr. Vijay Balu Raskar - Electrical Engineer
  • 21. In this, get heated due to eddycurrents and then heat transferred tocharge by radiation or convection.Secondary winding is metal container.Below part is situated in the ovenchamber which is made up of specialalloy which losses its magneticproperty and regain when they cooled. Mr. Vijay Balu Raskar - Electrical Engineer
  • 22. OperationWhen the primary winding is connected to the supply , theeddy currents gets induced in the metal container forming thwalls of the oven.Due to eddy currents, metal container gets heated and then itransferred to the charge by radiation.ACTION OF SPECIAL ALLOY:-Oven reaches its critical temperature . Magnetic circuit looses itsmagnetic property. Due to this reluctance of the magnetic circuitbecomes very high and inductive effect corrosponding decreases. Mr. Vijay Balu Raskar - Electrical Engineer
  • 23. Advantages:-1) Simple and foolproof method of temperature control2) 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
  • 24. Mr. Vijay Balu Raskar - Electrical Engineer