> I recently got a request to speed control a AC fan.
> (100W AC fan cost very much less than an DC fan, espesially also counting the
power supply...)
>
> If somebody have some experience on this, please give me some aid/tip/stories
about how to let smoke out of fans etc ;)
>
Most AC fans I come across are induction type motors.. as in squirrel
cage rotors.
The only real way to vary these suckers is to effectively change the
AC frequency being presented too it.

Other methods will cause increased slip but the motor speed will tend
to be very unreliable and even stall easily at lower speeds.
Phase angle is really for brushed motors like hand drills etc.

There are various methods for varying the AC freq but most involve
high freq switching as low freq iron transformers are large,
expensive and freq dependent.Also generation of an sine wave without
switching techniques (high freq) is very inefficient.

I know this is a vague rendering of the facts but you're brief was for
low freq and low cost.. bad luck.



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Lance Allen
Technical Officer
Uni of Auckland
Psych Dept
New Zealand
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