Electronics notes/Inductors and transformers

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Inductors

See also

http://electronics.stackexchange.com/questions/12930/capacitors-or-inductors

http://www.avrfreaks.net/forum/inductor-current-smoothing

Filters (application)

(compared to RC filters)

(Note: The L seems to refer to Lenz)

Choke (application)

✎ This article/section is a stub — some half-sorted notes, not necessarily checked, not necessarily correct. Feel free to ignore, or tell me about it.

Ferrite beads

Ferrite beads, also known as ferrite chokers, are designed to eat a certain range of frequencies, and turn it into (a negligible amount of) heat.

They work as inductors, and act as a passive low-pass filter.

One thing they address are that oscillators such as clock generators (and modern power supplies, since they're typically switch-mode) act as little radio-frequency transmitters, particularly when there is something around to act like an antenna, such as wires.

So high frequencies easily get around. While most things are fine with a little high frequency EM around, not always. So there's regulations about this.

You pass these tests by suppressing things. Ferrite beads can do this.

Note that often it's easier to suppress earlier (near the source) rather than later (on an external wire), meaning that ferrite beads are sometimes a sign of laziness.

And in some cases they're not particularly necessary for your case, but e.g. qualifying for worldwide RF emission tests made it easier to slap one onto the cable and be done with a single variant that passes worldwide.

Note that since they're inductors, mis-applied ferrite beads could cause resonance. So don't just slap on one you found somewhere because you think it will Magically Make Things Better.

See also:

• http://computer.howstuffworks.com/question352.htm
• http://images.google.com/images?q=ferrite+beads
• http://www.analog.com/en/analog-dialogue/articles/ferrite-beads-demystified.html

Transformers

Named purposes / designs

✎ This article/section is a stub — some half-sorted notes, not necessarily checked, not necessarily correct. Feel free to ignore, or tell me about it.

• isolation transformer

• control transformer

• instrument transformer

• modulation transformer

• Autotransformer

• Variable Autotransformer

• neon-sign transformer

• trigger transformer

Other design properties

• potted transformers, print transformers

• audio-frequency transformers

• power-frequency transformers - are designed for power transfer, at 50Hz

• multi-phase transformers

• grounding transformer

• distribution transformer