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Sci.Electronics.Basics -> Fan Motor
There are 13 messages in this thread.
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Sorry for such a simple question, but I've got a few 120mm
240V .125A (?30W) axial fans like a bigger version of the case
cooling fans in a computer.
I've set one up in a box with a large truck air filter so I can run it
24/7 to remove dust from my house atmosphere. At the moment, the
aircons and computers do it :)
Unfortunately these fans are a little too energy hungry and noisy.
What are my options for slowing them down a tad?
I thought of adding a resistance in line, but this would only
dissipate heat -- not lost in Winter, but a waste of money in Summer.
Then I thought about running two of these in series.
Is there any cheap and cheerful way to cut down on these over
enthusiastic, but otherwise great little ball bearing fans?
Thanks, jack
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Author: Rich WebbDate: 11:57 21-04-08
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On Mon, 21 Apr 2008 23:47:42 +0800, spamfree@spam.heaven wrote:
> Sorry for such a simple question, but I've got a few 120mm
>240V .125A (?30W) axial fans like a bigger version of the case
>cooling fans in a computer.
>
>I've set one up in a box with a large truck air filter so I can run it
>24/7 to remove dust from my house atmosphere. At the moment, the
>aircons and computers do it :)
>
>Unfortunately these fans are a little too energy hungry and noisy.
>
>What are my options for slowing them down a tad?
>
>I thought of adding a resistance in line, but this would only
>dissipate heat -- not lost in Winter, but a waste of money in Summer.
>
>Then I thought about running two of these in series.
>
>Is there any cheap and cheerful way to cut down on these over
>enthusiastic, but otherwise great little ball bearing fans?
PWM is the usual way. Some good discussion at
<http://www.cpemma.co.uk/pwm.html>;
--
Rich Webb Norfolk, VA
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Author: john jardineDate: 18:44 21-04-08
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<spamfree@spam.heaven> wrote in message
news:98dp045ig5umlufvpp2n2c58hgag6ldbl3@4ax.com...
> Sorry for such a simple question, but I've got a few 120mm
> 240V .125A (?30W) axial fans like a bigger version of the case
> cooling fans in a computer.
>
> I've set one up in a box with a large truck air filter so I can run it
> 24/7 to remove dust from my house atmosphere. At the moment, the
> aircons and computers do it :)
>
> Unfortunately these fans are a little too energy hungry and noisy.
>
> What are my options for slowing them down a tad?
>
> I thought of adding a resistance in line, but this would only
> dissipate heat -- not lost in Winter, but a waste of money in Summer.
>
> Then I thought about running two of these in series.
>
> Is there any cheap and cheerful way to cut down on these over
> enthusiastic, but otherwise great little ball bearing fans?
>
> Thanks, jack
Just wire it to a lamp dimmer.
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Author: Michael A. TerrellDate: 22:56 21-04-08
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john jardine wrote:
>
> Just wire it to a lamp dimmer.
Not a good idea. There are speed controls made for ceiling fans that
will work, though.
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On Mon, 21 Apr 2008 23:47:42 +0800, spamfree@spam.heaven wrote:
> Sorry for such a simple question, but I've got a few 120mm
>240V .125A (?30W) axial fans like a bigger version of the case
>cooling fans in a computer.
>
>I've set one up in a box with a large truck air filter so I can run it
>24/7 to remove dust from my house atmosphere. At the moment, the
>aircons and computers do it :)
>
>Unfortunately these fans are a little too energy hungry and noisy.
>
>What are my options for slowing them down a tad?
>
>I thought of adding a resistance in line, but this would only
>dissipate heat -- not lost in Winter, but a waste of money in Summer.
>
>Then I thought about running two of these in series.
>
>Is there any cheap and cheerful way to cut down on these over
>enthusiastic, but otherwise great little ball bearing fans?
Thanks guys. I'll look for a fan speed controller, but I guess they
usually only come cheap with fans?
I've read that a transformer would be OK.
I see a cheapie 36V that would suit.
What speed would the fan likely do (fraction of full speed) at 36V?
Perhaps around half speed, if the curve I/rpm is logarithmic?
Then someone suggested a diode in one lead. Is that liable to damage
the motor? Perhaps a tranny is safer.
I don't really need a variable speed, just roughly halve the full
rate.
Cheers, jack
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On Tue, 22 Apr 2008 14:25:24 +0800, spamfree@spam.heaven wrote:
>On Mon, 21 Apr 2008 23:47:42 +0800, spamfree@spam.heaven wrote:
>I've read that a transformer would be OK.
>I see a cheapie 36V that would suit.
>What speed would the fan likely do (fraction of full speed) at 36V?
>Perhaps around half speed, if the curve I/rpm is logarithmic?
Could someone check my calculation, please?
The motor draws 125mA at 240V.
So at 36V, it should draw roughly 36/240 x 125 = 18.75 mA
The VA (~Watts) here will be 18.75 x 36/1000 = 0.675 W
Which will cost me ~ $1 per annum to run.
What would be the approximate efficiency of the transformer?
Cheers, jack
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Author: amdxDate: 08:09 22-04-08
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<spamfree@spam.heaven> wrote in message
news:dm2r04t2j4338o9ge3rjbmqe7rck34086d@4ax.com...
> On Tue, 22 Apr 2008 14:25:24 +0800, spamfree@spam.heaven wrote:
>
>>On Mon, 21 Apr 2008 23:47:42 +0800, spamfree@spam.heaven wrote:
>
>>I've read that a transformer would be OK.
>>I see a cheapie 36V that would suit.
>>What speed would the fan likely do (fraction of full speed) at 36V?
>>Perhaps around half speed, if the curve I/rpm is logarithmic?
>
> Could someone check my calculation, please?
>
> The motor draws 125mA at 240V.
> So at 36V, it should draw roughly 36/240 x 125 = 18.75 mA
> The VA (~Watts) here will be 18.75 x 36/1000 = 0.675 W
> Which will cost me ~ $1 per annum to run.
>
> What would be the approximate efficiency of the transformer?
>
> Cheers, jack
At some point the voltage will be to low to start the motor, it will run
if pushed, it just won't start.
My favorite solution is to use a series capacitor (non polarized, voltage
appropriate) to drop some of the voltage. The capacitor is smaller than a
transformer and produces much less heat than a resistor.
I don't have the math ability to calculate the proper capacitance and you
don't know what voltage you want on the fan. So use a transformer, resistor,
or variac to find the proper speed then measure the voltage across the
motor. With the wanted voltage known, someone on here can calculate the
proper capacitance.
I would try putting the two fans in series that may be the simplest
solution.
Anyone know how to model that motor in LTspice. Is it as simple as an
inductor? (or as complicated :-))
Mike
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Author: AlanDate: 12:14 22-04-08
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spamfree@spam.heaven wrote:
> On Tue, 22 Apr 2008 14:25:24 +0800, spamfree@spam.heaven wrote:
>
>> On Mon, 21 Apr 2008 23:47:42 +0800, spamfree@spam.heaven wrote:
>
>> I've read that a transformer would be OK.
>> I see a cheapie 36V that would suit.
>> What speed would the fan likely do (fraction of full speed) at 36V?
>> Perhaps around half speed, if the curve I/rpm is logarithmic?
>
> Could someone check my calculation, please?
>
> The motor draws 125mA at 240V.
> So at 36V, it should draw roughly 36/240 x 125 = 18.75 mA
> The VA (~Watts) here will be 18.75 x 36/1000 = 0.675 W
> Which will cost me ~ $1 per annum to run.
>
> What would be the approximate efficiency of the transformer?
>
> Cheers, jack
You're assuming that the current draw is linear over a wide range of
source voltage.
This is a mistake.
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Author: Michael A. TerrellDate: 12:25 22-04-08
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spamfree@spam.heaven wrote:
>
> Thanks guys. I'll look for a fan speed controller, but I guess they
> usually only come cheap with fans?
Home improvement stores sell them as an accessory for ceiling fans in
the US. You should have something similar in Oz.
--
http://improve-usenet.org/index.html
Use any search engine other than Google till they stop polluting USENET
with porn and junk commercial SPAM
If you have broadband, your ISP may have a NNTP news server included in
your account: http://www.usenettools.net/ISP.htm
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Author: Rich GriseDate: 19:37 22-04-08
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On Mon, 21 Apr 2008 23:47:42 +0800, spamfree wrote:
> Sorry for such a simple question, but I've got a few 120mm
> 240V .125A (?30W) axial fans like a bigger version of the case
> cooling fans in a computer.
>
> I've set one up in a box with a large truck air filter so I can run it
> 24/7 to remove dust from my house atmosphere. At the moment, the
> aircons and computers do it :)
>
> Unfortunately these fans are a little too energy hungry and noisy.
>
> What are my options for slowing them down a tad?
>
> I thought of adding a resistance in line, but this would only
> dissipate heat -- not lost in Winter, but a waste of money in Summer.
>
> Then I thought about running two of these in series.
>
> Is there any cheap and cheerful way to cut down on these over
> enthusiastic, but otherwise great little ball bearing fans?
It depends on what kind of motor. Different types use different
methods of controlling the speed. Most of them don't like just
reducing the voltage to them. Do you have any more information
about the motor, like a brand name, part number, maybe a nameplate
with some information?
Thanks,
Rich
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On Tue, 22 Apr 2008 23:37:04 GMT, Rich Grise <rich@example.net> wrote:
>It depends on what kind of motor. Different types use different
>methods of controlling the speed. Most of them don't like just
>reducing the voltage to them. Do you have any more information
>about the motor, like a brand name, part number, maybe a nameplate
>with some information?
Thanks for your help Rich.
The fan is a Sirocco brand.
Model YX2517
Ball bearing
AC230/240V 50Hz
125 mA
Impedance Protected
Made in Taiwan
That was from the label on the fan.
The cattledog says:
Air volume 3 m^3/min
rpm 3000
Input Watts 17
Current 125 mA
Noise 47 dBA
Maybe a diagnostic feature is that it freewheels without any cogging
for a long time after you switch it off. I guess that means there are
no permanent magnets in it.
I realise that it would be the ideal to buy another fan with less
current draw, but these are what I've got, and I can't see anything
more suitable. These were spot on, on paper, just that the acid test
shows them to be noisy little buggers -- I should have investigated
that 47 dB :)
Cheers, jack
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Author: Rich GriseDate: 18:53 24-04-08
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On Wed, 23 Apr 2008 12:32:32 +0800, spamfree wrote:
> On Tue, 22 Apr 2008 23:37:04 GMT, Rich Grise <rich@example.net> wrote:
>
>>It depends on what kind of motor. Different types use different
>>methods of controlling the speed. Most of them don't like just
>>reducing the voltage to them. Do you have any more information
>>about the motor, like a brand name, part number, maybe a nameplate
>>with some information?
>
> Thanks for your help Rich.
>
> The fan is a Sirocco brand.
> Model YX2517
> Ball bearing
> AC230/240V 50Hz
> 125 mA
> Impedance Protected
> Made in Taiwan
>
> That was from the label on the fan.
>
> The cattledog says:
> Air volume 3 m^3/min
> rpm 3000
> Input Watts 17
> Current 125 mA
> Noise 47 dBA
>
> Maybe a diagnostic feature is that it freewheels without any cogging
> for a long time after you switch it off. I guess that means there are
> no permanent magnets in it.
>
> I realise that it would be the ideal to buy another fan with less
> current draw, but these are what I've got, and I can't see anything
> more suitable. These were spot on, on paper, just that the acid test
> shows them to be noisy little buggers -- I should have investigated
> that 47 dB :)
>
Well, it sounds like it's definitely probably maybe an induction motor.
Controlling the speed of an induction motor, short of a VFD, is kind of
out of my league - maybe try a google (or any handy search engine) search
on "control induction motor speed" or the like.
Good Luck!
Rich
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On Thu, 24 Apr 2008 22:53:14 GMT, Rich Grise <rich@example.net> wrote:
>Well, it sounds like it's definitely probably maybe an induction motor.
>
>Controlling the speed of an induction motor, short of a VFD, is kind of
>out of my league - maybe try a google (or any handy search engine) search
>on "control induction motor speed" or the like.
Thanks, Rich, I've done some reading and it seems that small fans on
mains power are generally large-slip motors which are amenable to
speed control with voltage, as opposed to most induction motors that
approach synchronous speeds and not much away from that.
Now, I calculated that this fan has an "effective resistance" of
around 3.3 kOhms. I happen to have a 3.3 kOhm 10W resistor handy and
so I connected it in series with this fan.
The fan ran magnificently. Just about right, maybe a little faster
would be better, but perfectly quiet and acceptable.
Unfortunately, after about 3 minutes, the resistor was so hot it could
have burned me. I know that wirewound cement resistors can run really
hot, but this appeared to be absorbing more Watts than my calculation
would have led me to believe.
The motor says it draws 0.125 A but the catalogue says "input Watts
17" So I assume that that current is startup current. And the running
current is actually 17/240 = 0.071 A.
I suppose the effective resistance (reactance, impedance and all that)
of the motor can only be found by measurement, so it's possible that
the resistor was absorbing anything up to about 15W in the circuit
that I tried it.
Anyways, that is going to be too expensive to run 24/7.
I can't seem to find a transformer that would drop 240VAC to around
150VAC or so. I have a book of calculations for making your own
transformers, is this an efficient possibility?
Perhaps stripping out the secondary of an existing tranny and rewiring
to suit? Are big transformers less efficient than one just above
specs? Do you know of an easier way to efficiently drop the mains
voltage to two thirds?
Disclaimer : All advice taken without any implied responsibility of
the adviser. Rest assured that I treat electricity with all the
paranoia it deserves. No touchy when plugged in!
Cheers, and thanks, jack
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