Lance Allen wrote

>The only real way to vary these suckers is to effectively change the
>AC frequency being presented too it.

Yep, used such controllers.  Far too expensive for this...

>Other methods will cause increased slip but the motor speed will tend
>to be very unreliable and even stall easily at lower speeds.

I have one spare pin, possible to use for feedback using a magnet mounted in center of fan, and a cheap bipolar hall sensor close to it.

>Phase angle is really for brushed motors like hand drills etc.

Therefor I will try pulsing x number of cycles and y cycles pause instead.

Anybody done that?

I will start testing by mounting a temperature sensor in the windings...

>There are various methods for varying the AC freq but most involve
>high freq switching as low freq iron transformers are large,
>expensive and freq dependent.Also generation of an sine wave without
>switching techniques (high freq) is very inefficient.
>
>I know this is a vague rendering of the facts but you're brief was for
>low freq and low cost.. bad luck.

Thank you... ;)

/Morgan
Morgans Reglerteknik, HŠllekŒs, 277 35 KIVIK, SWEDEN
   tel +46(0)414-446620, fax -70331,   mrt@iname.com