"Ron" wrote in message
...
On Tue, 12 Aug 2003 18:53:57 GMT, "Trevor Wilson"
wrote:


"Arny Krueger" wrote in message
...
"WindsorFox[SS]" wrote in message
news:jW_Za.10115$qf.4685@lakeread06

Right, I wondered what a 12 Volt fan had to do with your question,
it's so cross posted now I thought I'd missed something and was just
replying to the 12V comments.

I plead guilty to bringing up 12 volt fans. I did so because 12 volt
fans
are plentiful and readily adjustable. They can be adapted for use where
the
original fan was 12 volt when DC power is readily available, such as in
a
power amp.

I've experimented with fan speed controls on 120 VAC fans, and had
disappointing results. 120 VAC fans are based on synchronous motors and
IME
they get pretty ugly at low speeds if you turn their speed way down.

**Then you're not doing it right. With simple series resistors and a
decent
fan, speed reductions of at least 40% may be obtained very easily,
cheaply
and reliably.

Further proof that little knowledge is worse than no
knowledge at all. He was taking about SYNCHRONOUS MOTORS.
Putting resistors in series with a synchronous motor is
folly.

**You would, of course, be wrong. It is a widely used practice, for slowing
FANS using shaded pole motors down to lower speeds. You seem to be
forgetting that although fans use sychronous motors, they are under
constant, heavy load. As such, they can never reach the theoretical
synchronous speed, which is determined by the number of poles and the
frequency of operation. As such, use of a resistor (or even a cap) is a most
effective form of speed control.

And again, I refer you to the original poster's requirement that the speed
control be SIMPLE.


--
Trevor Wilson
www.rageaudio.com.au