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Choke (electronics) 1
Choke (electronics)
A choke, with two 47mH windings and rated to
handle 0.6A
A choke is a coil of insulated wire, often wound on a magnetic core,
used as a passive inductor which blocks higher-frequency alternating
current (ac) in an electrical circuit while passing signals of much lower
frequency and direct current by having an impedance largely
determined by reactance, which is proportional to frequency. Chokes
are typically used as the inductive components in electronic filters.
The name comes from blocking —"choking" —high frequencies while
passing low frequencies. It is a functional name; the same inductor is
often called a "choke" if used to block higher frequencies, but a "coil"
or "inductor" if, say, part of a tuned circuit.
Types and construction
An MF or HF radio choke for tenths of an
ampere, and a ferrite bead VHF choke for several
amperes.
Chokes used in radio circuits are divided into two classes – those
designed to be used with power and audio frequencies, and the others
to be used with radio frequencies.
Audio frequency coils, usually called A.F. chokes, usually have
ferromagnetic iron cores to increase their inductance. Chokes were
used as filters, in conjunction with large electrolytic capacitors, in
power supplies; working at low power-line frequencies they were
large, heavy, and expensive, but more effective and power-efficient
than resistor-capacitor hum filters. Modern components and circuits,
with very large and cheap electrolytic capacitors and electronic circuits
which suppress hum, have long made chokes obsolete in
mains-frequency power supplies, although small and inexpensive
inductors are used in high-frequency switch-mode power supplies.
Chokes for higher frequencies often have iron powder or ferrite cores (see Ferrite bead). They are often wound in
complex patterns (basket winding) rather than regularly to reduce self-capacitance. Chokes for even higher
frequencies have non-magnetic cores and low inductance.
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Choke (electronics) 2
Common-mode choke
Common-mode chokes, where two coils are wound on a single core, 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. They pass differential currents (equal but opposite), while
blocking common-mode currents.[1]
A typical common-mode choke configuration. The common mode currents, I1 and I2, flowing in the same direction through each of the choke
windings, creates equal and in-phase magnetic fields which add together. This results in the choke presenting a high impedance to the common mode
signal.[2]
References
[1] http:/ / www. murata. com/ products/ emc/ knowhow/ pdf/ 26to30. pdf
[2] "Understanding Common Mode Noise" (http:/
/
www.
pulseelectronics.
com/
download/
3100/
g019&
ei=NN-NT9WtDMuugQfI3LT8DQ&usg=AFQjCNG7o36UcFFK_bblUwgluE2GUM74ZQ& sig2=htX-bGkrbazkg-hWQgWcPA). Pulse. . Retrieved 17 April 2012.
External links
• Chokes Explained (http:/ / www. aikenamps.com/ Chokes. html)
• Common Mode Choke Theory (http:/ / www. butlerwinding. com/ store. asp?pid=28349)
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Article Sources and Contributors 3
Article Sources and ContributorsChoke (electronics) Source: http://en.wikipedia.org/w/index.php?oldid=501430329 Contributors: A930913, Amallam, Armstrong1113149, Bushben, CaptainTickles, Chevymontecarlo, DV8
2XL, DanielDeibler, Dcshank, Denisarona, Dicklyon, DieSwartzPunkt, Erodium, Foobaz, Frap, FredYork, Hooperbloob, JJ Harrison, Jmeden2000, Keenan Pepper, Kinkreet, KnightRider, Lukit,
Man pl, Mike1024, Nnh, Nsaa, Omegatron, Peak, Pol098, Prari, Quibik, Rabogliatti, Reddi, Redheylin, Richmond8255, Shaddack, Ssd, Steve carlson, SvNH, Thorseth, Tprentice, Utcursch,
Vhann, WordSurd, Yves-Laurent, 44 anonymous edits
Image Sources, Licenses and ContributorsImage:Choke electronic component Epcos 2x47mH 600mA common mode.jpg Source:
http://en.wikipedia.org/w/index.php?title=File:Choke_electronic_component_Epcos_2x47mH_600mA_common_mode.jpg License: Public Domain Contributors: Mike1024
File:Two ferrite beads.jpg Source: http://en.wikipedia.org/w/index.php?title=File:Two_ferrite_beads.jpg License: Creative Commons Attribution 2.0 Contributors:
http://flickr.com/photos/oskay/
File:Common-mode-choke.png Source: http://en.wikipedia.org/w/index.php?title=File:Common-mode-choke.png License: Public Domain Contributors: CaptainTickles, Hazard-SJ,
Ww2censor
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