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'[EE]:: Ceiling fan speed control using simple TRIA'
The Freescale app note below suggests that a typical ceiling fan
induction motor can be speed controlled using a basic phase controlled
Fan and dimmer and I are not to hand as I write, so rather than going
and blowing uo a dimmer in the pursuit of knowledge, what do people
think of this?
If single phase motors can be speed controlled this was then people
would do it in droves.
I have severe doubts about this circuit.
But, Freescale must be right. No?
|On 28 Mar 2012 at 17:13, RussellMc wrote:
> The Freescale app note below suggests that a typical ceiling fan
> induction motor can be speed controlled using a basic phase controlled
> TRIAC "dimmer".
> Fan and dimmer and I are not to hand as I write, so rather than going
> and blowing uo a dimmer in the pursuit of knowledge, what do people
> think of this?
> If single phase motors can be speed controlled this was then people
> would do it in droves.
> I have severe doubts about this circuit.
> But, Freescale must be right. No?
Yeah, the correct way to do inductive motor speed control is to vary frequency, but that's too expensive. But I'm thinking a fan load has something going for it that migh allow this cheap voltage chopping method to be of some use. The speed torque curve of a fan slowly ramps up from 0 till fan gets up near operating speed then load rises dramatically. If the range of useful fan speeds was say 90-100% to give say 25-100% air flow, variable voltage and fixed freq could probably be quite useable.
-- Brent Brown, Electronic Design Solutions
9 Titoki Place, Pukete,
Hamilton 3200, New Zealand
Ph: +64 7 849 0069
Fax: +64 7 849 0071
Cell: +64 27 433 4069
|At 11:13 PM 3/27/2012, RussellMc wrote:
>If single phase motors can be speed controlled this was then people
>would do it in droves.
>I have severe doubts about this circuit.
>But, Freescale must be right. No?
Large industrial ceiling fans installed in warehouses normally come with a speed control which is nothing more than a lamp dimmer that is optimized for inductive loads. The speed pot is also wired backwards - when you rotate it clockwise from the OFF position, the speed is at maximum. That's an attempt to ensure that fan actually begins to rotate.
What they are doing is entirely reasonable if you think of the motor as having just enough torque to spin the fan at its maximum safe speed. Chopping the waveform reduces the torque, which then reduces the speed.
This technique does NOT work for motors that either are much larger than the torque load or for motors that have varying mechanical loads. Ceiling fans just happen to be the correct combination of limited motor torque and proportional load as the speed is varied.
-- Dwayne Reid <planet.eon.net> dwayner
Trinity Electronics Systems Ltd Edmonton, AB, CANADA
(780) 489-3199 voice (780) 487-6397 fax
Custom Electronics Design and Manufacturing
On Thu, Mar 29, 2012 at 1:45 PM, Spehro Pefhany <interlog.com> wrote: speff
> My understanding is that you're just lowering the torque of the
> motor, but with a fan that equates to lowering the speed.
Hm...would that work with standard household plug in portable fans? I
have a couple that I like a lot, but I'd like to have a bit of
granularity between 'gale force' and 'off'.
-- A common mistake that people make when trying to design something
completely foolproof is to underestimate the ingenuity of complete
> > My understanding is that you're just lowering the torque of the motor,
> > but with a fan that equates to lowering the speed.
> Hm...would that work with standard household plug in portable fans? I have a couple
> that I like a lot, but I'd like to have a bit of granularity between 'gale force'
> and 'off'.
(VBG) I know what you mean. I would expect it to work fine. I would try it with a light dimmer controller first.
-- Scanned by iCritical.
I've spent a number of years in the home automation industry primarily on the lighting control side and ceiling fan speed control is always in demand for these systems. The route most companies take is using capacitors tied in series to relays to give a system 3-4 speeds. Even the cheap fan speed control switches you can purchase at stores like Home Depot use capacitors. It's something about the reactance of the cap. One company had and engineer who made it his mission to design a ceiling fan controller using TRIACS and he gave up due to a variety of hurdles, finally agreeing that capacitors were the best way to do it.
'[EE]:: Ceiling fan speed control using simple TRIA'
Thanks - yes, I bought the magazine today from Jaycar NorthShore due
to that article.
They do seem to be doing things more properly than some. Both their
MPPT projet and this one show some real thinking about real world
issues - or maybe they have really good app notes :-).
On 2 April 2012 15:35, IVP <clear.net.nz> wrote: joecolquitt
> Thanks - yes, I bought the magazine today from Jaycar NorthShore
> due to that article.
I'm quite keen to make one. I've intentions to build a couple of tools
that could use induction motors and speed control. The only half-decent
controllable one I've got presently is a hefty 12VDC winch motor,
that I might possibly build a scroll saw around
Which I could use the
> MPPT project
for to keep a battery topped up (in conjunction with a PC PSU).
Although I don't think we'll be seeing much sun for a few days
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