On Jul 18, 9:01*pm, Paul G. wrote:
On Mon, 18 Jul 2011 21:35:26 -0300, Paul G.
wrote:



On Mon, 18 Jul 2011 06:31:03 -0700 (PDT), klem kedidelhopper
wrote:

On Jul 18, 9:22*am, klem kedidelhopper
wrote:
On Jul 17, 6:30*am, "Michael A. Terrell"
wrote:

klem kedidelhopper wrote:

On Jul 16, 7:35 pm, "Michael A. Terrell"
wrote:
klem kedidelhopper wrote:

We have a ceiling fan in our bedroom that we sometimes like to run at
very slow speed at night. The fan was purchased as new surplus many
years ago and never came with a speed control. So I have been using a
generic solid state speed controller. With this unit we are able to
take the unit down to complete "crawl" however there has always been a
slight rhythmic buzzing noise whose loudness and duty cycle are both
directly proportional to the motor speed. I know it's related to the
pulse type of control I'm using but short of just using a variac or a
rheostat for that matter, does anyone know of a method to achieve a
very slow speed without the noise?

Also this motor has no brushes and so even though its not labeled as
such I wonder if it could be a "Universal" type of motor that could
run on DC? It wouldn't take much to put a bridge and perhaps even a
filter in the electrical box ahead of the motor. I'm thinking that DC
operation could possibly be quieter. Thanks, Lenny

* *Is the speed controler made for induction motors?

How would a speed controller made for induction motors differ from say
an ordinary lamp dimmer?

* *Lamp dimmers are simple phase controllers. *They aren't designed for
inductive loads. That's why most light dimmers can't be used on
Florescent lights. *They can cause the motor to overheat at some speeds,
and cause it to be noisy or erratic at low speeds.

Leviton makes variable speed fan controls with a slider to set the
speed. You can get them at HD, Lowes or a lot of other building supply
stores.

http://www.leviton.com/OA_HTML/ibeCCtpSctDspRte.jsp?section=10857&min...

http://www.lowes.com/SearchCatalogDisplay?Ntt=speed+control&langId=-1...

http://www.homedepot.com/webapp/wcs/stores/servlet/Search?keyword=spe...
--
It's easy to think outside the box, when you have a cutting torch.

Thanks Michael for sending me those dimmer links. They are pricey
though... Lenny

I did find the Leviton but it may not be a continuously variable unit.
I'll have to go look at them. Lenny

* I had a fan that was noisy like that, and stuck a 5-10 uF capacitor
in series with the motor. You can't use the dimmer - so you need a
switch to hook the fan either to the controller or the series cap. It
runs quite slowly, and no buzzing. Make sure the capacitor is designed
for line use ..... 250vac or 600vdc should be OK. If it fails, the fan
will just run at full speed. The only worry would be if it were to get
hot say from internal arcing or something wierd like that. To be one
the safe side use a U/L approved or type Z capacitor.
* You can cause the cap and inductance of the fan to resonate....
That will cause voltages greater than the line voltage to appear
across the fan motor, and it go fast, and overheat. Try a few
capacitors, starting at 1uf, and increase until you get the speed you
want.
* Some fans have a switch that gives 3-4 speeds, with a series cap,
you can effectively get a much slower range of speeds, and thereby not
need to use a dimmer type speed controller.

Paul G.

* That should be a "X" type capacitor, not a "Z" type. It's
questionable that you need either X or Y types.

* From an Illinois Capacitor blurb on capacitors:
" These capacitors are divided into 2 classifications, X and Y. X
class capacitors are capacitors that are connected line to line and in
the event of failure of the capacitor the potential for electrical
shock is not present. X capacitors are further subdivided into three
subcategories X1, X2 and X3. X1 capacitors are used where the peak
voltage the capacitors will be greater than 2500 volts and less than
4000V. Class X2 capacitors are in applications where the peak voltage
is equal to below 2500 volts. X3 capacitors are used where the peak
voltage is less than or equal to 1200 volts. X2 capacitors are the
most common.
Y capacitors on the other hand are connected from line to ground. They
are typically a very low capacitance value. In the event a Y capacitor
fails the potential for electrical shock is present. Y capacitors are
also subdivided into four subcategories, Y1, Y2, Y3 and Y4. Y1
capacitors are used with voltages up 500Vac, Y2 are used with voltages
up to 300Vac,Y3 are used with voltages up to 250Vac and Y4 capacitors
are used up to 150Vac.
X class capacitors are rated up to 660Vac and Y capacitors are
manufactured with voltage ratings up to 440Vac.
X class capacitors are manufactured with a variety of dielectric
materials. This includes polyester, polypropylene, ceramic and paper
while Y capacitors are typically produced out of ceramic and paper
dielectrics. With the exception of ceramics the capacitors are
produced using metallized materials and may be impregnated with epoxy
or mineral oils."

I'm thinking that the fan draws about 1.0 amp. Therefore that current
would be passing through the capacitor. I do have lots of capacitors
as well as a 5 position tapped transformer type speed control from
another fan. The problem with that control though is that slow speed
is not slow enough. Perhaps I could put the capacitor in series with
slow position and see what that will do. I never thought of doing
this. Lenny