Reducing speed of AC axial cooling fan

[techie_alison]

Hello,

Would it be an approach to insert a resister in series with one of the
supply leads?

I've replaced two old fans where the bearings had gone and were rattling,
the replacements are very clean running but so fast and even noisier.

It's two of these fans btw,
http://www.rapidelectronics.co.uk/rkmain.asp?PAGEID=80010&CTL_CAT_CODE=&STK_
PROD_CODE=M70817&XPAGENO=1

Thanks kindly,

techie_a

 

[techie_alison]

I've replaced two old fans where the bearings had gone and were rattling,
the replacements are very clean running but so fast and even noisier.

Solution to connect the two fans in series across the supply. Quiet and
running freely with noticable airflow.

Hope this was ok...

 

[Chris]

Solution to connect the two fans in series across the supply. Quiet and
running freely with noticable airflow.

Hope this was ok...

Hi, Alison. Maybe not. Check the motor temp.

By the way, the link isn't working. Could you specify the make&model,
or the seller p/n?

Chris

 

[techie_alison]

Hi, Alison. Maybe not. Check the motor temp.

By the way, the link isn't working. Could you specify the make&model,
or the seller p/n?

Chris

Hi Chris, sure, http://www.rapidelectronics.co.uk part# is 37-0975 .

Admittedly have had the device running for 30-60 mins or so and it's a
little warmer there than I'd like, a guess of about 25oC to 30oC. A friend
has suggested a light dimmer (too bulky), resistors, or indeed a diode to
chop the waveform.

How do 3W wirewound resistors sound? A guess at the ohms to get the rpm
down to 1250 from 2500 would be handy, not too up on the VCR/PVC forumlas
and how they apply here. I have a choice anywhere between 30R and 4k7.

Thanks

Aly

 

[Sjouke Burry]

Hello,

Would it be an approach to insert a resister in series with one of the
supply leads?

I've replaced two old fans where the bearings had gone and were rattling,
the replacements are very clean running but so fast and even noisier.

It's two of these fans btw,
http://www.rapidelectronics.co.uk/rkmain.asp?PAGEID=80010&CTL_CAT_CODE=&STK_
PROD_CODE=M70817&XPAGENO=1

Thanks kindly,

techie_a

Dont put in a resistor, a starting motor
needs a lot of current,and it will stall
that much easier when getting older.
Lower the voltage instead.
I used a 500 ohm potmeter and an emittor
follower npn power transistor for that purpose.
That way you have all the current you need,
at any voltage you want.

 

[John Larkin]

Hi Chris, sure, http://www.rapidelectronics.co.uk part# is 37-0975 .

Admittedly have had the device running for 30-60 mins or so and it's a
little warmer there than I'd like, a guess of about 25oC to 30oC. A friend
has suggested a light dimmer (too bulky), resistors, or indeed a diode to
chop the waveform.

For an AC fan, do *not* use a dimmer or a diode. It's a shaded-pole
induction motor and will not take kindly to either.

A power resistor will work, although it will get warm. Calculate the
motor impedance in ohms (rated fan voltage divided by rated current)
and start with a resistor of equal value, and power rating equal to
fan (volts*amps) to be on the safe side. It doesn't take a lot of
voltage reduction to make a fan noticably quieter, so a smaller
resistor could work.

John

(Yes, motors are reactive loads, but this is close enough.)

 

[Phil Allison]

"Sjouke Burry"

Dont put in a resistor,

** Nonsense - it works fine.

You can use a series cap instead.

a starting motor
needs a lot of current,

** Not one of these fan motors.

They are "impedance protected" and inherently current limited.

Lower the voltage instead.
I used a 500 ohm potmeter and an emittor
follower npn power transistor for that purpose.

** NO WAY !!!

It is a 240 volt AC fan - you half wit !!




............ Phil

 

[Jasen Betts]

Hello,

Would it be an approach to insert a resister in series with one of the
supply leads?

I've seen that done before, also capacitors and inductors.
the last two have the advantage of wasting less energy.
Bye.
Jasen

 

[ehsjr]

By the way, the link isn't working. Could you specify the make&model,
or the seller p/n?

Chris

Yep - you gotta watch the line wrap. This bit needs to
be pasted to the link: PROD_CODE=M70817&XPAGENO=1

Ed

 

[techie_alison]

For an AC fan, do *not* use a dimmer or a diode. It's a shaded-pole
induction motor and will not take kindly to either.

A power resistor will work, although it will get warm. Calculate the
motor impedance in ohms (rated fan voltage divided by rated current)
and start with a resistor of equal value, and power rating equal to
fan (volts*amps) to be on the safe side. It doesn't take a lot of
voltage reduction to make a fan noticably quieter, so a smaller
resistor could work.

John

(Yes, motors are reactive loads, but this is close enough.)

Hi

PVC = 240v * 0.1amps = 24watts

VCR = 240v / 0.1amps = 2400 Ohms

http://www.rapidelectronics.co.uk Stock # 62-8128

Tempted to buy a couple of 1K and see where that goes, bit of a stab in the
dark this as don't want to end up with a bag of different power resistors
that will never be used. Might have some high wattage resistors of unknown
values (right now) back at home.

Aly

 

[techie_alison]

Yep - you gotta watch the line wrap. This bit needs to
be pasted to the link: PROD_CODE=M70817&XPAGENO=1

Ed

Hi Ed

You know, every time I do this (mess up links), find out how to do it, then
forget again.

It needs to be quoted in < > doesn't it?

 

[techie_alison]

Dont put in a resistor, a starting motor
needs a lot of current,and it will stall
that much easier when getting older.
Lower the voltage instead.
I used a 500 ohm potmeter and an emittor
follower npn power transistor for that purpose.
That way you have all the current you need,
at any voltage you want.

noted. May research that for another application actually.

 

[techie_alison]

I've seen that done before, also capacitors and inductors.
the last two have the advantage of wasting less energy.
Bye.
Jasen

Yes, supplied this link from a friend which describes the various methods;

http://www.vintage-radio.com/repair-restore-information/valve_dropper-calcs.
html

Aly

 

[techie_alison]

http://www.vintage-radio.com/repair-restore-information/valve_dropper-calcs.
html

Aly

oh bloody hell!! have done it again......... real apologies people.

 

[Tony Williams]

How do 3W wirewound resistors sound? A guess at the ohms to get
the rpm down to 1250 from 2500 would be handy, not too up on the
VCR/PVC forumlas and how they apply here. I have a choice
anywhere between 30R and 4k7.

Maybe a 5-10VA 230:24V mains transformer, wired
as an autotransformer.


230Vin-------+
|
*)
'24V' )
)
|
+----> 208V out
|
*)
'230V' )
)
|
N------------+---->

A 10% reduction in voltage is usually enough
to reduce the noise.

 

[Phil Allison]

"techie_alison"

PVC = 240v * 0.1amps = 24watts

VCR = 240v / 0.1amps = 2400 Ohms

http://www.rapidelectronics.co.uk Stock # 62-8128

Tempted to buy a couple of 1K and see where that goes,

* They will need to be 10 watt rated ones.

Or, try one or two 1 uF, 250 volt caps.

1 uF = 3200 ohms at 50 Hz.



......... Phil

 

[Phil Allison]

"Tony Williams"

A 10% reduction in voltage is usually enough
to reduce the noise.

** By 1 dB maybe!

To get a 6dB noise reduction, the voltage has to drop to about 170 volts.




......... Phil

 

[ehsjr]

oh bloody hell!! have done it again......... real apologies people.

Just add the words "watch the line wrap in the above".
Most folks know to paste on the bit that wraps.

Ed

 

[Rich Grise]

Just add the words "watch the line wrap in the above".
Most folks know to paste on the bit that wraps.

http://www.tinyurl.com is also pretty frickin' handy, e.g.:
http://tinyurl.com/gwuhl

Cheers!
Rich

 

[JeffM]

This bit needs to

every time I do this (mess up links),
It needs to be quoted in < > doesn't it?
techie_alison

Won't help.
Usenet groups that don't have *binary* or *binaries* in their names
are ASCII-only.
(There is no such thing as *formatting*).
Either the servers and the newsreaders handle URLs properly,
or they don't.