RE: Intelligent AC motor control

["Neil Ball" <neilball@xxxxxxxxxxxxxxx>]

Don't know if there are any long term problems but I have been asked
to
provide speed control of motors from lighting dimmer modules on previous
projects. As these modules are cutting out the relevant parts of the AC
sine
wave then power is definitely reduced accordingly. I've always provided a
suitable disclaimer as the motors are not lighting (obviously) so the
dimmers are not designed with this kind of load in mind. That said some
have
been in for more than 6 years now and both fan and dimmer are still working
fine. The original installations were all made using Leax lighting controls
- leading edge 10A dimmers, the latter are via Helvar - 1kW universal
dimmer
modules generally set to trailing edge dimming.



Is there a better speed controller for your unit? I have a Vent Axia
Airminder and it has the speed control built-in and uses a timer to switch
between low speed (overnight), normal (daytime) and boost.



Neil B.



_____

From: ukha_d@xxxxxxx [mailto:ukha_d@xxxxxxx] On Behalf Of
David Chapman
Sent: 08 August 2007 16:36
To: ukha_d@xxxxxxx
Subject: [ukha_d] Intelligent AC motor control



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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