> I buy those 5 inch 240 VAC muffin fans at Dayton and
> just wire them into the 120 VAC wall outlet. They run
> at half the speed and are extremely quiet. I use one on
> top of my 2 meter mobile rig in the shack, which likes
> to run hot, and used to have one on top of my amp to
> help exhaust the hot air. Phil KB9CRY
>
[Steve Katz] I realize that this works to some extent; however, I
have been unsuccessful in quantifying actual results because the AC motors
run on reduced voltage have a great reduction in torque and thus cannot spin
well against back pressure. When I run a standard 240V 125cm (4.25")
"Boxer" type fan on 120V, I can stall it with the tip of my finger very
easily, no damage done to finger. Same fan run on 240V cannot be stalled in
this manner. The obvious decrease in torque is that -- very obvious. As
such, when I run the "reduced voltage" fan against the back pressure of a
tightly integrated enclosure, it develops almost no air flow, as compared
with the fan run on its intended voltage. So, I guess my question is: Has
anyone qualified rpm and torque vs. airflow w/backpressure, say 0.2" or 0.3"
(what might be typically found in an amateur amp using linear flow cooling
above chassis)? Thanks! -WB2WIK/6
> > At 08:23 AM 7/22/02 -0700, Steve Katz wrote:
> > > //What "reduced voltage" are you talking about? I'd like to hear
> > >more about operating AC fans on reduced voltage, I was never successful
> > >doing this. (I do operate DC brushless fans on "reduced voltage" to
> reduce
> > >rpm and noise, and this works, with reduced airflow, of course.)
> >
> > I just wired them in series. Definitely slows them down and quiets
> them.
> >
> >
> > 73, Pete N4ZR
> >
> > Check out the World HF
> > Contest Station Database at
> > www.pvrc.org
> >
> >
> >
> >
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