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electric furnace:see furnacefurnace,
enclosed space for the burning of fuel. There are many kinds of furnaces, the type depending upon the fuel and the use to which the heat produced within it is put. Most familiar are the furnaces used in the heating of buildings.
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a melting or heating furnace in which the thermal effect of an electrical phenomenon is used.
According to the manner in which electric energy is converted into heat, the following types of electric furnaces are distinguished: arc furnaces, induction furnaces, resistance furnaces, electron-beam furnaces, and equipment for dielectric heating. Depending on the area of application, electric furnaces may be classified as industrial furnaces, laboratory furnaces, or furnaces for comfort heating.
The important characteristics of electric furnaces are the working medium, the type of current or the frequency of the current, and design. The working medium may be air, a corrosive atmosphere, or an inert atmosphere.
Electric furnaces may be used for manufacturing, heat engineering, or electrical engineering purposes. Therefore, one may speak of an electric-furnace installation.
An electric-furnace installation consists of an electric furnace, electric power equipment, auxiliary electrical equipment, switching equipment, instrumentation, pyrometric equipment, and an automatic control system. The electric power equipment includes furnace transformers, rectifiers, high-frequency generators, and tube generators. The auxiliary electrical equipment may include chokes, ballast resistors, capacitors, and plate-supply rectifiers. The switching equipment includes circuit breakers and disconnecting switches. Except for the electric furnace, all the components of an electric furnace installation are concentrated at a furnace power substation.
The size of an electric-furnace installation may be characterized by the installation’s capacity—that is, by its output of materials or finished products—or by the linear size of the furnace’s working chamber and the power rating of the electric power equipment.
REFERENCESElektrotermicheskoe oborudovanie: Spravochnik. Moscow, 1967.
Egorov, A. V., and A. F. Morzhin. Elektricheskie pechi. Moscow, 1975.
Farnasov, G. A., V. L. Rabinovich, and A. V. Egorov. Elektrooborudovanie i elementy avtomatizatsii elektroplavil’ nykh uslanovok: Spravochnik. Moscow, 1976.
A. V. EGOROV and A. F. MORZHIN
electric furnace[i¦lek·trik ′fər·nəs]
An enclosed space heated by electric power. The furnace may be in such forms as a refractory crucible, a large tiltable refractory basin with a capacity of 100 tons (91 metric tons) and a removable roof, or a long insulated chamber equipped with a continuous conveyor. Heat is provided by an arc to the charge or melt (direct-arc furnace), by an arc between electrodes (indirect-arc furnace), or by an arc confined for concentrated heating by an electromagnetic field (plasma-arc furnace). Heat may also be produced by current flowing in the melt. See Electrometallurgy, Pyrometallurgy
Because the source of heat is nonchemical, electric furnaces are especially desirable in melting alloys of controlled composition. Temperature is also readily controlled. The arc furnace may be used to smelt ores or to refine metals or alloys. Induction furnaces are widely used to melt alloys for castings. Because electric furnaces can be enclosed, they are used for operations that require controlled or inert atmospheres, such as growing crystals or annealing. When sealed and evacuated, they are used in degassing metals. Furnaces with hearth resistors are used for operations below melting temperatures, such as annealing, and with infrared heat lamps, for drying paints or setting glues. See Arc heating, Electric heating, Heat treatment (metallurgy), Kiln, Refractory