Induction furnaces principle

PHYSICAL PRINCIPLE
The principle of induction furnace is the Induction heating:
Induction heating is a form of non-contact heating for conductive materials.
The principle of induction heating is mainly based on two well-known physical phenomena:

  1. Electromagnetic induction
  2. The Joule effect

1) ELECTROMAGNETIC INDUCTION

The energy transfer to the object to be heated occurs by means of electromagnetic induction. Any electrically conductive material placed in a variable magnetic field is the site of induced electric currents, called eddy currents, which will eventually lead to joule heating.

2) JOULE HEATING
Joule heating, also known as ohmic heating and resistive heating, is the process by which the passage of an electric current through a conductor releases heat.
The heat produced is proportional to the square of the current multiplied by the electrical resistance.

  I2    R

Induction heating relies on the unique characteristics of radio frequency (RF) energy – that portion of the electromagnetic spectrum below infrared and microwave energy. Since heat is transferred to the product via electromagnetic waves, the part never comes into direct contact with any flame, and there is no product contamination.
Induction heating is a rapid, clean, and non-polluting heating.
The advantage of the induction furnace is a clean, energy-efficient and well-controllable melting process compared to most other means of metal melting.
Foundries use this type of furnace and now also more iron foundries are replacing cupolas with induction furnaces to melt cast iron, as the former emit lots of dust and other pollutants.

An high voltage electrical source from a primary coil induces a low voltage, high current in the metal, or secondary magnetic core. Induction heating is simply a method of transferring heat energy. Induction furnaces are ideal for melting and alloying a wide variety of metals with minimum melt losses, however, little refining of the metal is possible. There are two main types of induction furnace: coreless and channel.

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