Intelligent AC motor control

["David Chapman" <david@xxxxxxxxxx>]

Automated Home DiscussionI'm sure someone here will know the answer to
this.

I'm setting up a whole house heat recovery unit. This uses two radial AC
fans, each 240v 90w. One basically pushes air in to the house and one
pushes air out, both via a heat exchanger.

If I run them flat out all is fine, The power factor stays around 1 and
together they use about 180w. But I want to run them at reduced speed for
three reasons, I don't need the air flow rates all the time, I want to
reduce noise and of course want to reduce power consumption.

The system came with a fan speed controller but it's old technology (looks
1980s) and when I measure what it's doing although it reduces speed and
noise the fans seem to use almost the same quantity of electricity, it
appears to change the power factor which I recall isn't good.

I'm sure I've seen devices that reduce the speed AND power consumption of
AC fans / motors but I've been unable to find anything. Any ideas anyone ?

David C



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