10kW 400kHz Induction Heating Coil For Steel Melting Furnace

Water Cooling Induction Heating Coil For Steel Melting Furnace

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An induction coil consists of two coils of insulated wire wound around a common iron core (M).One coil, called the primary winding (P), is made from relatively few (tens or hundreds) turns of coarse wire.The other coil, the secondary winding, (S) typically consists of up to a million turns of fine wire (up to 40 gauge).

An electric current is passed through the primary, creating a magnetic field.] Because of the common core, most of the primary's magnetic field couples with the secondary winding.[citation needed] The primary behaves as an inductor, storing energy in the associated magnetic field. When the primary current is suddenly interrupted, the magnetic field rapidly collapses. This causes a high voltage pulse to be developed across the secondary terminals through electromagnetic induction. Because of the large number of turns in the secondary coil, the secondary voltage pulse is typically many thousands of volts. This voltage is often sufficient to cause an electric spark, to jump across an air gap (G) separating the secondary's output terminals. For this reason, induction coils were called spark coils.

What is induction coil (inductor)?

An Induction coil,also called a inductor,choke or reactor,is a passive two terminal electrical component that stores energy in a magetic field when electric current flows throw it.And inductor typically consists of an insulated wire wound into a coil around a core.

An induction furnace consists of a nonconductive crucible holding the charge of metal to be melted, surrounded by a coil of copper wire. A powerful alternating current flows through the wire. The coil creates a rapidly reversing magnetic field that penetrates the metal. The magnetic field induces eddy currents, circular electric currents, inside the metal, by electromagnetic induction. The eddy currents, flowing through the electrical resistance of the bulk metal, heat it by Joule heating. In ferromagnetic materials like iron, the material may also be heated by magnetic hysteresis, the reversal of the molecular magnetic dipoles in the metal. Once melted, the eddy currents cause vigorous stirring of the melt, assuring good mixing.
An advantage of induction heating is that the heat is generated within the furnace's charge itself rather than applied by a burning fuel or other external heat source, which can be important in applications where contamination is an issue.
Operating frequencies range from utility frequency (50 or 60 Hz) to 400kHz or higher, usually depending on the material being melted, the capacity (volume) of the furnace and the melting speed required. Generally, the smaller the volume of the melts, the higher the frequency of the furnace used; this is due to the skin depth which is a measure of the distance an alternating current can penetrate beneath the surface of a conductor. For the same conductivity, the higher frequencies have a shallow skin depth—that is less penetration into the melt. Lower frequencies can generate stirring or turbulence in the metal.
A preheated, one-tonne furnace melting iron can melt cold charge to tapping readiness within an hour. Power supplies range from 10kW to 42 MW, with melt sizes of 20 kg to 65 tonnes of metal respectively.