On 3 May 00, at 8:44, Mark Peterson wrote:

> I'm trying to make a speed control for a whole house fan I purchased.  The
> manufacturer warns in the instructions not to attempt to use a solid state
> speed control device with the fan.  This brings up a couple questons.
>
> 1.  Firing a triac at various angles to regulate power to a device is
> pretty straight forward.  Does the method used to do this vary depending
> whether you're dealing with a resistive load versus a reactive load like an
> induction motor?  Just how does motor speed control differ from a basic
> lamp dimmer?

Mark,

    AC  brushless motors have a non-linear response between supply
and speed, it's like a 220V lamp supplied from 180V to 220V, the
effect is negligible...a good but expensive choice is to modify supply
frequency...
        Asimple solution is to use a DC brush motor and to modifie with
a triac (thyristor and bridge, or transistor ) the efective amplitude of
supply, using a PWM algorithm.
Vasile
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Surducan Vasile, engineer
mail: vasile@l30.itim-cj.ro
URL: http://www.geocities.com/vsurducan
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