Reducing speed of AC axial cooling fan

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

rattling,

Hi Chris, sure,

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

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.

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.)

"Sjouke Burry"

** Nonsense - it works fine.

You can use a series cap instead.

** Not one of these fan motors.

They are "impedance protected" and inherently current limited.

** NO WAY !!!

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

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

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

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

Ed

Hi :)

PVC = 240v * 0.1amps = 24watts

VCR = 240v / 0.1amps = 2400 Ohms

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

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?

noted. May research that for another application actually.

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

html

Aly

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

In article , techie_alison wrote: [snip]

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.

--
Tony Williams.

"techie_alison"

• 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

"Tony Williams"

** By 1 dB maybe!

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

........ Phil

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

Ed

is also pretty frickin' handy, e.g.:

Cheers! Rich

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.