Speed control of exhaust fan

"John Dunkley"




** A variac will likely work just fine.

 So might a phase control dimmer designed to control fan motors.





.......   Phil

Electrical wholesaler will have plenty. Try this Clipsal one, but plenty
of others.

http://updates.clipsal.com/ClipsalOnline/ProductInformation.aspx?CatNoC2%032E500F&ref =

David

**Assuming the motor is a synchronous type, your chances are limited. PA's
idea of a VariacT is ideal, but expensive and bulky. I know people who have
put a lamp in parallel with the motor and used a standard light dimmer. I
can't guarantee the results, but it should work. Another good way is to
place the motor in series with a bridge rectifier (and the mains supply).
Across the DC connections of the bridge, connect a MOSFET (suitable rated
and heat sinked, of course) and vary the Gate Volts to get speed control
that way. The advantage is the motor can be varied over a very wide range.

Assuming the motor is a synchronous type, your chances are limited.


***** Wilson,you must be joking,an exhaust fan with a synchronous motor,the
mind boggles!!!

Brian Goldsmith.

On Thu, 13 Jul 2006 10:02:00 GMT, "Brian Goldsmith."


All domestic mains powered exhaust fans I have ever seen use a simple
shaded pole AC motor.  

I think a synchronous motor would be a bit over the top for an exhaust
fan :)

http://en.wikipedia.org/wiki/Shaded_pole_motor

**Call it a brain fart. Of course a standard induction motor will be the
type used. My other comments and suggestions remain.