On 8/3/2013 3:43 AM, Ashton Crusher wrote:
On Mon, 29 Jul 2013 20:45:02 +0000, passerby
wrote:

replying to The Daring Dufas , passerby wrote:
the-daring-dufas wrote:

You could try a regular light dimmer.



Small AC fans usually have shaded pole motors, RPM of which is frequency
dependent. By cutting off part of the phase with a light dimmer you will
just make it start even harder than it already is for this type of a
motor. There may be *some* RPM control due to torque losses when dimmer is
dialed down, but it's only a small percentage point around the designed
RPM, not from 0 to the max.

I've put dimmers on fans and all you do it trade off some fan blade
noise for increased motor noise because the solid state dimmers just
chop the current up and make the motor "buzz". The only way to do it
without the buzz is with an old fashioned transformer based
dimmer/motor controller.


Otherwise know as a variable autotransformer or Variac. The dimmers
using a triac instead of an SCR may be less likely to make the fan motor
buzz. I've seen Variac light dimmers used in recording studios
because they don't make the lights buss or add noise to the electrical
power for the studio. ^_^

https://en.wikipedia.org/wiki/Autotransformer

http://www.variac.com/

TDD