# Induction Heating

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## induction heating

[in′dək·shən ¦hēd·iŋ]
(engineering)
Increasing the temperature in a material by induced electric current. Also known as eddy-current heating.

## Induction Heating

the heating of current carriers through the generation of electric currents in them by an alternating electromagnetic field. The power released in a conductor by induction heating depends on the dimensions and physical properties of the conductor (specific electric resistivity and relative magnetic permeability), as well as on the frequency and intensity of the magnetic field. In induction heating the electromagnetic field is supplied by induction heaters.

Induction heating is characterized by the nonuniform release of power in the object being heated. Eighty-six percent of the power is released in the surface layer (the so-called penetration). The penetration of the current Δ (in meters) is Δ = where ρ is the specific electrical resistivity in ohms • m, μ, is the relative magnetic permeability, and f is the frequency in hertz (Hz).

Low-frequency (50 Hz), medium-frequency (up to 10 kHz) and high-frequency (over 10 kHz) currents are used in induction heating to generate an alternating electromagnetic field. Mechanical and static converters, as well as tube oscillators, are used to supply medium- or high-frequency current to induction heaters.

Induction heating is most widely used in the melting of metals, zone melting, and heating for pressure shaping. Induction heating is the most advanced contactless method of transmitting electrical energy to the object being heated, converting electrical energy directly into thermal energy. A schematic diagram of a device using induction heating is shown in Figure 1.

Figure 1. Schematic diagram of an induction heating device: (1) power supply, (2) capacitor, (3) induction heater, (4) lined crucible, (5) object being heated

### REFERENCES

Babat, G. I. Induktsionnyi nagrev melallov i egopromyshlennoe primenenie. 2nd ed. Moscow-Leningrad, 1965.
Elektrotermicheskoe oborudovanie: Spravochnik. Moscow, 1967.

A. B. KUVAIDIN

## Induction heating

The heating of a nominally electrical conducting material by eddy currents induced by a varying electromagnetic field. The principle of the induction heating process is similar to that of a transformer. In the illustration, the inductor coil can be considered the primary winding of a transformer, with the workpiece as a single-turn secondary. When an alternating current flows in the primary coil, secondary currents will be induced in the workpiece. These induced currents are called eddy currents. The current flowing in the workpiece can be considered as the summation of all of the eddy currents.

In the design of conventional electrical apparatus, the losses due to induced eddy currents are minimized because they reduce the overall efficiency. However, in induction heating, their maximum effect is desired. Therefore close spacing is used between the inductor coil and the workpiece, and highcoil currents are used to obtain the maximum induced eddy currents and therefore high heating rates. See Core loss

Induction heating is widely employed in the metalworking industry for a variety of industrial processes. While carbon steel is by far the most common material heated, induction heating is also used with many other conducting materials such as various grades of stainless steel, aluminum, brass, copper, nickel, and titanium products. See Brazing, Heat treatment (metallurgy), Soldering

The advantages of induction heating over the conventional processes (like fossil furnace or salt-bath heating) are the following: (1) Heating is induced directly into the material. It is therefore an extremely rapid method of heating. It is not limited by the relative slow rate of heat diffusion in conventional processes using surface-contact or radiant heating methods. (2) Because of skin effect, the heating is localized and the heated area is easily controlled by the shape and size of the inductor coil. (3) Induction heating is easily controllable, resulting in uniform high quality of the product. (4) It lends itself to automation, in-line processing, and automatic-process cycle control. (5) Startup time is short, and standby losses are low or nonexistent. (6) Working conditions are better because of the absence of noise, fumes, and radiated heat. See Electric heating

## induction heating

In piping, the heat treatment of completed welds by the heat generated by the use of induction coils around the piping.
References in periodicals archive ?
The company's DIOS hybrid electric range has two induction heat burners and one radiant heat burner.
In an installation where several shafts having slightly different parameters were being induction heated, the tool monitor picked up a fault reading that indicated an unanticipated change in part size.
Nakaoka, "Latest developments of high-frequency series load resonant inverter type built-in cooktops for induction heated all metallic appliances," in 2009 IEEE 6th International Power Electronics and Motion Control Conference.
In 1963, it introduced the world's first induction heated roll.
Another advance is the use of induction heated platen to heat molds; improved temperature uniformity is claimed for the induction heated platens.
Thus, induction heats the charge directly, rather than the furnace.
A complex-shaped automotive manifold was mounted on a table supported on six legs that raised, lowered, and tilted the part at various angles to permit insertion of numerous induction heated inserts.
The horizontal coreless induction heated section is built into the fully enclosed pouring vessel as a flow-through section between the fill and the stopper pouring sections.
New applications, dating back to the Pressure Pouring Process introduced by Lebanon Steel Foundry in 1960, often combine induction heated pouring/refining ladies with the counter-gravity pouring scheme.
Casting occurs in a uniquely designed (approximately 4 x 1 ft., 1800 kg [4000 lb]) induction heated casting furnace.

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