Special fan - 115VAC 3

[zoobz]

I'm looking for a special 120mm axial 115VAC fan that has high amps and pressure ratings for an experiment of mine. So far, all I've found is high amp and pressure 12VDC fans. I'm wondering why I can't find the same in a 115VAC fan? Any good sources out there? Thanks

 

[edfair]

google "muffin fan". You'll find suppliers.

Ed Fair
Give the wrong symptoms, get the wrong solutions.

 

[mscallisto]

I've had good luck here:

http://www.thermalfx.com/merchant2/

click Fans > AC Fans

I did see a 119mm 115v but only looked through a few listings

sam

 

[kjv1611]

Hmm, muffin fan, hu? Learn somethin' new every day.

Is a muffin fan that much better than a typical computer fan? I mean, does it really blow THAT much more air, and still remain quiet?

What's the benefit of one of those? Any real world usage experience by anyone here?

--

"If to err is human, then I must be some kind of human!" -Me

 

[zoobz]

What I'm now thinking is that DC amps are waaaaay different than AC amps...apples and oranges.

I've been all through the muffin and axial fan searching...
Thanks

 

[zoobz]

I can't edit the above but I think I've figured it out.

The amps aren't different...just the scale. Since Amps= watts/volts, by only using a 12VDC fan, it shoots the amps up to 5a. But by using a 115VAC fan, the same formula only shows as .18a or so...

So are these the same force?

 

[DTracy]

kjv1611 -

I have had some experience with muffin fans. It depends on the specs of the fan as to whether the output is higher or not. At the time it was the only fan of that size that could be used. Worked ok, but now I would use the 12 volt version for the same project.

Regards,
David

 

[BadBigBen]

So are these the same force?

NO...



Ampere is not a force, but the definition of approx. 6.242x10^18 electrons passing a certain point per sec., also called a Coulomb ... See:

http://en.wikipedia.org/wiki/Ampere

Force is the concept used to describe how a mass is affected in form of acceleration or mech. stress... See:

http://en.wikipedia.org/wiki/Force

now there is "Ampère's force law", which is a totally different fruit (Peach), and should not be confused with the apples (Amps) nor the oranges (Force)...

Ben
"If it works don't fix it! If it doesn't use a sledgehammer..."
How to ask a question, when posting them to a professional forum.
Only ask questions with yes/no answers if you want "yes" or "no"

 

[zoobz]

I think it explains the high rating of amps with DC fans versus the low ratings of amps with AC fans.

15watts/12VDC = 1.25a
15watts/115VAC = .13a

What do you think?

 

[Nelviticus]

It's the resistance of the fans: V = IR, or Voltage (volts) = Current (amps) x Resistance (ohms).

So 12V and 1.25A means the resistance must be 9.6 ohms. 115V and 0.13A means the resistance must be ~884 ohms.

Unless I've forgotten my school physics (it was 30 years ago).

Nelviticus

 

[goombawaho]

Let me take a step back and ask this question (not jumping this thread though):

Are there any drawbacks or negatives in having an AC fan inside a computer. Like inducing electrical noise that might get into the sound card/speaker output??

 

[BadBigBen]

Are there any drawbacks or negatives in having an AC fan inside a computer

Yes, as it could cause EMI(RFI), and could, if installed by dope, e.g. if the cables are loosely attached, come off at any time and cause a short that would knock out the system, at best, or cause a fire, at the worst of it...


as to EMI, judge yourself:

Electromagnetic interference (or EMI, also called radio frequency interference or RFI) is a disturbance that affects an electrical circuit due to either electromagnetic conduction or electromagnetic radiation emitted from an external source. The disturbance may interrupt, obstruct, or otherwise degrade or limit the effective performance of the circuit. The source may be any object, artificial or natural, that carries rapidly changing electrical currents, such as an electrical circuit, the Sun or the Northern Lights.

source:

http://en.wikipedia.org/wiki/Radio_interference

a DC fan has NO CHANGING CURRENT, as it runs only in one direction, where as the AC fan has a rapid changing current (either 60Hz or 50Hz, depending on where you live in the world)...


Ben
"If it works don't fix it! If it doesn't use a sledgehammer..."
How to ask a question, when posting them to a professional forum.
Only ask questions with yes/no answers if you want "yes" or "no"

 

[zoobz]

quoting wiki...oh brother...big help that is

 

[BadBigBen]

quoting wiki...oh brother...big help that is

knocks the quotes but does not back up HIS opinion, and that is what it is, YOUR OPINION, nothing more nothing less...

and just stating that it is of NO HELP, does not invalidate the information given...

I normally just leave it at that, but I am in a bickering mood, and will point you to another reference or two:

Electromagnetic Interference (EMI) is caused by undesirable radiated electromagnetic fields or conducted voltages and currents. The interference is produced by a source emitter and is detected by a susceptible victim via a coupling path. The coupling path may involve one or more of the following coupling mechanisms:

1. Conduction - electric current
2. Radiation - electromagnetic field
3. Capacitive Coupling - electric field
4. Inductive Coupling - magnetic field

Conducted noise is coupled between components through interconnecting wires such as through power supply and ground wires. Common impedance coupling is caused when currents from two or more circuits flow through the same impedance such as in power supply and ground wires.

Radiated electromagnetic field coupling may be treated as two cases. In the near field, E and H field coupling are treated separately. In the far field, coupling is treated as a plane wave coupling.

Electric field coupling is caused by a voltage difference between conductors. The coupling mechanism may be modeled by a capacitor.

Magnetic field coupling is caused by current flow in conductors. The coupling mechanism may be modeled by a transformer.

Some typical external noise sources into a radio receiver include radiated electric field coupling from: high-voltage power lines, broadcast antennas, communications transmitters, vehicle ignition systems and electric machinery. Most conducted coupling from external sources occurs through the ac power lines.

Typical radio interference to other equipment includes radiated electric field coupling to: TV sets, broadcast receivers, telephone lines, appliances, and communications receivers. Most conducted coupling to other equipment occurs through the ac power lines.

source: eEngineer - Intorduction: EMI, EMC, RFI

http://www.radioing.com/eengineer/intro.html

Electromagnetic Interference (EMI), defined by NATO as an electromagnetic disturbance which interrupts, obstructs, or otherwise degrades the effective performance of electronic or electrical equipment.

Source: DUH, NATO...

for further reading I would suggest:

AGARD LS-177
Electromagnetic Interference and Electromagnetic Compatibility
(InterErences Electromagnktiques et Compatibilitk Electromagnktique)
Copyright AGAKD 1991
ISBN 92-835-0620-0

and

Electromagnetic Interference
Brian Mordick, RCDD and Trent Jones, Hoffman with contributions by Abdi Jama
Ecnmag.com - July 01, 2004

http://www.ecnmag.com/electromagnetic-interference.aspx?menuid=580

Ben
"If it works don't fix it! If it doesn't use a sledgehammer..."
How to ask a question, when posting them to a professional forum.
Only ask questions with yes/no answers if you want "yes" or "no"

 

[goombawaho]

Ok boys, let's not start a "pull out your sources" competition here.

I guess for general computing as long as you install the AC fan safely and securely with no wires dangling, it should be okay.

But for my PC where I'm recording vinyl to disk, I wouldn't want that potential extra source of noise. That's why I mentioned it

 

[edfair]

Using AC in computers was no problem in the "old" days. One I was around used 4 per bay and there were 28 bays.

Power required to run them is mostly a function of air volume, ie "work" independent of (but result of) voltage and current.

Some that I built up at IBM PC timeframe used AC as those were all that were available to move the amount of air I wanted to pull through.

One issue: using AC fans in a PC would require an AC distribution harness. Since the load is minimal it is easier (cheaper) to use the DC distribution. And building the little ones as AC would be difficult.

AC fans use male connectors so the connectors are an insulated socket. You couldn't short something without trying.

About the AC issues: If you recall the AT power supplies with front power switches you would remember the power cable dangling down along side the motherboard. Never seemed to bother anything other than being a pain when it came time for M/B replacement.

Ed Fair
Give the wrong symptoms, get the wrong solutions.

 

[BadBigBen]

Ed, I remember those days too, where the hardware was pretty much solid and short of a nuclear blast would survive almost anything, heck I still have three PC'S (not IBM compatible) around that still work like a charm...

goombawaho - you are right, to a point, in that it is pointless to argue, where biased views are concerned...

Ben
"If it works don't fix it! If it doesn't use a sledgehammer..."
How to ask a question, when posting them to a professional forum.
Only ask questions with yes/no answers if you want "yes" or "no"

 

[edfair]

You may have seen some BBB, but I suspect you saw later versions. The ones that really had the air movers were in service before you were born and were retired before you hit grade school. (based on your profile) All transistor using RTL with core memory. At the same time there were tube based ones still in service that needed even more air.
I have several pre IBMPC (my build) in boxes awaiting reassembly. They are SWTP based but hardware hacked to make them usable. I packaged them in 19" rack Scientific Atlanta set top cases bought surplus when they started using a smaller case.


Ed Fair
Give the wrong symptoms, get the wrong solutions.

 

[BadBigBen]

Ah, I see Ed, yup, that was before my time...

the oldest system that I ever touched was an C3 Data System, came with a walloping 32 Kilobyte of mem, 11 TTY and 5 VTerminals, two 8" floppies, and I believe a 10 MB HDD the size of a VW Beetle (well not quite that big but to a kid it sure looked like it)...



Ben
"If it works don't fix it! If it doesn't use a sledgehammer..."
How to ask a question, when posting them to a professional forum.
Only ask questions with yes/no answers if you want "yes" or "no"

 

[kjv1611]

So really, unless you have a very specific need for a Muffin fan, or any AC fan for that matter (when it comes to computers), it is best to just not mess with them anyway.

Just in case I ever ran into that, I'm glad I asked.

--

"If to err is human, then I must be some kind of human!" -Me