Choke

(electricity) An inductance used in a circuit to present a high impedance to frequencies above a specified frequency range without appreciably limiting the flow of direct current. Also known as choke coil.
(electromagnetism) A groove or other discontinuity in a waveguide surface so shaped and dimensioned as to impede the passage of guided waves within a limited frequency range.
(mechanical engineering) To increase the fuel feed to an internal combustion engine through the action of a choke valve. choke valve
(ordnance) A narrowing toward the muzzle in the bore of gun, hence the choked bore; often applied to shotguns.
(petroleum engineering) A removable nipple inserted in a flow line to control oil or gas flow.

An inductor that is used to prevent electric signals and energy from being transmitted along undesired paths or into inappropriate parts of an electric circuit or system. Power-supply chokes prevent alternating-current components, inherent to a power supply, from entering the electronic equipment. Radio-frequency chokes (RFCs) prevent radio-frequency signals from entering audio-frequency circuits. The printed circuit boards used in virtually all electronic equipment such as computers, television sets, and high-fidelity audio systems typically have one or more chokes. The purposes of these chokes are the (1) attenuation of spurious signals generated in the equipment itself so that these signals will not be transmitted to other parts of the circuit or beyond the overall system to other electronic devices; (2) prevention of undesired signals or electrical noise generated in other parts of the system from adversely affecting circuit performance; and (3) prevention of ripple from the power supply from degrading system behavior. Waveguide chokes keep microwave energy from being transmitted to the wrong part of a waveguide system. See also Electrical noise; Electronic power supply; Printed circuit; Ripple voltage; Waveguide.

In its simplest form, a choke or an inductor is a coil of wire (usually copper) wound around and insulated from a core, which may or may not be ferromagnetic. Ferromagnetic cores tend to increase inductance, reduce physical size, and reduce electromagnetic coupling between circuit elements, and they may increase power loss and resultant heating. Such cores often lead to nonlinear or swinging chokes, commonly found in power supplies, where the nonlinearity may be an advantage. See also Inductance; Inductor.

Inductor used to oppose the flow of alternating current.

It has been suggested that this article or section be merged with inductor. (Discuss)

For other uses, see choke.

A choke, with two 47mH windings and rated to handle 0.6A

A choke is an inductor designed to block (have a high reactance to) a particular frequency in an electrical circuit while passing signals of much lower frequency or direct current.

Contents 1 Description 2 Types and construction 3 Solid-state chokes 4 External links

Description

Choke coils are inductances that isolate AC frequency currents from certain areas of a radio circuit. Chokes depend upon the property of self-inductance for their operation. They can be used to block alternating current while passing direct current (contrast with capacitor). Common-mode choke coils are useful in a wide range of prevention of electromagnetic interference (EMI) and radio frequency interference (RFI) from power supply lines and for prevention of malfunctioning of electronic equipment.

Types and construction

Chokes used in radio circuits are divided into two classes – those designed to be used with audio frequencies, and the others to be used with radio frequencies. Audio frequency coils, usually called A.F. chokes, can have ferromagnetic iron cores to increase their inductance. Chokes for higher frequencies (ferrite chokes or choke baluns) have ferrite cores. Chokes for even higher frequencies have air cores. Radio frequency coils, (R.F. chokes), usually don't have iron cores. In high power service so much heat would be produced in making and destroying the field in the core that the coil would burn up.

Solid-state chokes

Solid-state chokes (SSC) can manage higher currents than traditional chokes. It reduces the high frequency buzzing noise when running under high electrical currents.

External links

• Chokes Explained
• Common Mode Choke Theory

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