induction coil

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induction coil

a transformer for producing a high voltage from a low voltage. It consists of a cylindrical primary winding of few turns, a concentric secondary winding of many turns, and often a common soft-iron core
Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005

induction coil

[in′dək·shən ‚kȯil]
A device for producing high-voltage alternating current or high-voltage pulses from low-voltage direct current, in which interruption of direct current in a primary coil, containing relatively few turns of wire, induces a high voltage in a secondary coil, containing many turns of wire wound over the primary.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

Induction coil

A device for producing a high-voltage alternating current or high-voltage pulses from a low-voltage direct current. The largest modern use of the induction coil is in the ignition system of internal combustion engines, such as automobile engines. Devices of similar construction, known as vibrators, are used as rectifiers and synchronous inverters. See Ignition system

The illustration shows a typical circuit diagram for an induction coil. The primary coil, wound on the iron core, consists of only a few turns. The secondary coil, wound over the primary, consists of a large number of turns.

Induction coils of a different type are used in telephone circuits to step up the voltage from the transmitter and match the impedance of the line. The direct current in the circuit varies in magnitude at speech frequencies; therefore, no interrupter contacts are necessary. Still another type of induction coil, called a reactor, is really a one-winding transformer designed to produce a definite voltage drop for a given current. See Reactor (electricity)

McGraw-Hill Concise Encyclopedia of Engineering. © 2002 by The McGraw-Hill Companies, Inc.


A coil of wire that generates a magnetic field when current is passed through it. The strength of the magnetic field is measured in henrys (H). When the current is removed, as the magnetic field disintegrates, it "induces" a brief current in the opposite direction of the original. Thus "electromagnetic induction" is caused by the opening and closing of a DC circuit or the continuous changing of directions in an AC circuit.

High-Frequency Filters
An induction coil impedes the flow of high-frequencies in an AC circuit, which is why inductors are used as surge protectors, choking off any high-frequency shifts. The tiny donuts placed on the end of signal cables and the load coils placed into telephone networks are examples. See electromagnetic induction.
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References in periodicals archive ?
(12)-(21), the total magnetic flux [[PHI].sub.1](x, [x.sub.1], t), [x.sub.1] [member of] [0,x] in the TCR-antenna induction coils is calculated for several shunt points.
For this position of the induction coil on the vertical axis of symmetry the macroflows in the lower part of the pool are directed downwards, and those in the upper part of the pool are directed upwards with the formation of a convex section on the surface of molten metal.
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During service, the ladle filled with the molten metal is placed inside the induction coil. Power is supplied to the coil and the metal is heated to the required temperature with simultaneous alloying and refining.
For higher applied frequencies of current in induction coil, the heating rate increases.
Induction Coil Designs and Applications (Micah Black, inductor design supervisor, Inductoheat, Inc.).
During the force measurement, current is servoed through the force induction coil to maintain the angular orientation of the pulley in one position.
The induction coil can be placed in or on the mould, or between the open mould halves.
* calculation of distribution of the electromagnetic field, produced with application of the induction coil inside and outside the drop and distribution of Lorenz forces, acting on the molten drop;
Each zone used either four mica band heaters consuming a total of 3.2 kw or an induction coil driven by an inverter that delivered 2 kw.
Celsio units feature a high frequency induction coil with 10 kW power that delivers fast shrinking for 3-32 mm diameter carbide tools and 6-32 mm diameter HSS toolholders.
Machined from lengths of a magnetodielectric material, the new induction coil concentrates magnetic flux locally on the part, rather than distributing it over a wide area, Ruffini said.