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 9EE605A.15to16

Recap In this class you have learnt about Different methods of temperature control of resistance heating 9EE605A.15to16

Objectives On completion of this topic, you would be able to know Arc furnace Different types of Arc Furnaces 9EE605A.15to16

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

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

Types of electric Arc Furnaces 1. Direct Arc furnace 2. Indirect Arc furnace 9EE605A.15to16

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. 9EE605A.15to16

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 9EE605A.15to16

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 9EE605A.15to16

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 9EE605A.15to16

Indirect Arc Furnace Fig.3 9EE605A.15to16

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

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

Indirect Arc Furnace Advantages High flexibility High melting Economical High efficiency 9EE605A.15to16

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

Summary In this class we have discussed about Arc heating Different types of electric arc furnaces Applications of arc furnaces 9EE605A.15to16

Quiz 1.Most common application of direct arc furnace is To produce steel Melting of non-ferrous metals Both a & b None 9EE605A.15to16

Quiz 2. Single phase direct arc furnace is also called Boy furnace Baby furnace Indirect arc furnace None 9EE605A.15to16

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 9EE605A.15to16

THANK YOU 9EE605A.15to16