From: Joseph Legris
X-Mailer: Mozilla 4.77 [en]C-SYMPA (Win95; U)
Subject: Re: Is it possible to run a shaded pole AC motor at half speed?
Date: Wed, 11 Sep 2002 13:38:42 -0400
NNTP-Posting-Date: Wed, 11 Sep 2002 13:32:58 EDT
Organization: Bell Sympatico
Wayne Whitney wrote:
> My bathroom fan is too loud, and I can't change it because I rent. So
> I was wondering if there is some way to provide the option of running
> it at half speed. The fan motor is a shaded pole AC motor, and the
> specifications on the fan say "not for use with solid state fan
> controls". I assume that rules out the readily available fan
> I understand from reading a January, 2002 thread that it is hard to do
> speed control on single-phase motors, so perhaps I am asking the
> impossible. The following possibilities did come to mind, though:
> 1) Change the frequency of the AC supply to 30Hz. Is there any simple
> way to do this other than an AC to DC to AC circuit? Is a shaded
> pole motor designed only for a particular frequency, say as far as
> the location of the shadings, or will it work at half frequency?
> 2) Change the voltage of the AC supply. I believe that a very low end
> motor like this runs with a lot of slip. Is it possible that by
> lowering the voltage I could increase the slip to as much as 50%?
> Would that be bad for the motor?
> 3) Add another tap to the winding in the stator. This might be tricky
> to do, but if I could tap the motor winding in the middle, then
> would running with half the winding halve the magnetic field
> strength and increase the slip? Would that be bad for the motor?
> Any comments would be welcome, thanks.
> Best wishes, Wayne
> P.S. How do three-speed ceiling fans do their speed control?
Buy a new fan. It's got to be cheaper/easier than any of the above.