Cooling fans - is the AC frequency a factor?

I am building a piece of equipment for the aircraft industry that uses a 115V 400Hz electrical supply. I have found I need to fit a cooling fan (like a PC one but a bit wider - about 5 inches diameter) and have got a 120V 50/60Hz one. Will this work? Impedance wise a higher frequency would mean less current drawn by what is presumably a mainly inductive load, but my main query is are fan rotation speeds related to the AC supply frequency? If so I guess trying to run a fan at about 7 times it's rated speed would not be a good idea so I haven't yet tried it.

Reply to
Steve
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Get a proper 400 Hz fan or run a DC fan off a DC supply.

If there's anyplace you don't want to be screwing around with "will it work" solutions, it's the aircraft industry!

And the answer is: It almost certainly won't work.

-- sam | Sci.Electronics.Repair FAQ:

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Reply to
Samuel M. Goldwasser

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I am not 'screwing around' with a 'will it work' solution and the equipment is not for on aircraft use. It is a simple bench test unit that only has a 115V 400Hz supply. As I am not being paid for the making of it I wish to see if I can use what equipment is available, rather than purchase bits I may not get refunded for; so less of the sarcasm please. As you do not know if it will work or not why bother replying?

Reply to
Steve

Do you blatantly ignore the ratings on other components? You can get away with putting too much voltage on a capacitor, or extra watts into a resistor, but not for very long.

With an AC fan, most are designed for a limited frequency range. The inductance and laminations and RPM are geared for a rather narrow range.

Most likely the 60Hz fan will refuse to spin. If it does spin, it will be way below synchronous speed and you'll get very little torque out of it.

The traditional way out is to use a fan running off some handy DC supply.

Reply to
Ancient_Hacker

I didn't detect an ounce of sarcasm in Sam's reply. He answered you matter-of-factly, and I totally agree with everything he said. Your original post stated that the device was for the "aircraft industry", implying that it would probably be used on or around an airplane. In retrospect, I would certainly have deduced the same thing that Sam did. Your original post would certainly have avoided all this if you had been more specific about the device, and where it would be used. We could care less about your financial arrangements with whomever you are building it.

An AC fan motor is almost certainly a synchronous type, meaning that its speed is totally dependent on the frequency of the power source. It would likely go up in smoke within a few seconds.

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Dave M
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Reply to
DaveM

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Nice attitude.

Reply to
Meat Plow

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the FAQs.

He DOES know and you ARE screwing around but fortunately no one will die from your work.

G=C2=B2

Reply to
stratus46

Seconded on every comment. Sam's replies and scribblings are well respected on this group, and if you can't listen without getting unnecessarily arsey, then perhaps you are asking your question in the wrong place ...

Arfa

Reply to
Arfa Daily

the

He did answer your question, it won't work.

Reply to
PeterD

the

Sadly, you don't know that. Since the OP has been less than honest, can't read replies, who knows what he's doing.

Reply to
PeterD

i'm pretty sure a 50/60 cycle fan wouldn't work; i agree with the guy who suggested a DC one. plenty of DC muffin fans around, and DC is universally producable. on the other hand, i don't know anything about airplane equipment, although i still have an old war surplus 400 hz motor/generator knocking around somewhere.

Reply to
z

I once ran some ham equipment (which used a linear 12v power supply) from a 400 Hz surplus generator. It worked well. The only way I could tell was instead of hearing a slight 60 Hz hum in the receive audio, I heard a slight 400 Hz hum. I felt like I was listening to flight attendant announcements in a DC-9. To this day, the PA system in DC-9's have that hum. By "to this day", I mean flying in an AirTran Boeing 717 which was the final configuration of the DC-9 before they went out of production. Sorry. Just rambling... None of this has anything to do with running an AC fan.

Reply to
greenpjs

| I am not 'screwing around' with a 'will it work' solution and the | equipment is not for on aircraft use. It is a simple bench test unit | that only has a 115V 400Hz supply. As I am not being paid for the | making of it I wish to see if I can use what equipment is available, | rather than purchase bits I may not get refunded for; so less of the | sarcasm please. As you do not know if it will work or not why bother | replying?

  1. Learn to read.
  2. Learn to ask questions.
  3. Learn about usenet.

For 1. you're on your own. For 2. you will have to provide the relevant information to get a usefull answer. For 3. answers are for free but you cannot make demands.

As for the original question, read Sams answer.

petrus bitbyter

Reply to
petrus bitbyter

On Tue, 14 Oct 2008 17:35:17 -0400, greenpjs put finger to keyboard and composed:

While we're rambling, I wonder how a mains frequency digital flip clock would run on a 400Hz supply, assuming it survived the experience. I reckon it would make an excellent bundy clock. Here in Australia we'd cut our working days to one hour ... just enough time for lunch. Time would fly.

- Franc Zabkar

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Reply to
Franc Zabkar

These are synchronous motor-driven.

Better to hack a digital clock. :)

-- sam | Sci.Electronics.Repair FAQ:

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Reply to
Samuel M. Goldwasser

I once worked at an avionics manufacturer and one of the pieces of lab equipment was a variable frequency AC mains generator. We took a spare one and sneaked a hidden cord to the time clock. We called it the "overtime generator".

Reply to
nobody >

I worked on avionics equipment for a lot of years. I retired in 1997. Back in 1966 while in the Air Force, fresh out of Avionics school. I was sure a

115 vac 400 cycle transformers would work just fine on 60 cycles. "I was young and knew every thing." An old Master Sargent wired up a 400~ 115 volt transformer to 60~s. He said watch and learn. Within 15 minutes the transformer overheated and started to smoke. I've remembered that lesson all these years. Transformers and induction motors are frequency sensitive. Has to do with current flowing in the core of the transformer. Some test equipment is designed to run on both 60 and 400 cycles.

I would be very careful using 60 cycles in circuit designed for 400 cycles. I think in most cases it will not work. If you do try to run the equipment on 60 cycles. Be sure to not leave it unattended even for a short period of time because when it starts overheating smoke and fire will be close behind.

Reply to
Jim Wheeler

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