On Wed, 31 Jan 2007 18:54:40 GMT, "Don Kelly" wrote:

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"Ross Herbert" wrote in message
.. .
On 30 Jan 2007 11:49:20 -0800, wrote:

Deep down I already know the answer to this is NO, but on the off
chance someone knows something I don't...

I have an old Lincoln "buzz box" welder with a dead cooling fan. Parts
to fix will run $76 and change.

I also have a Radio Shack 120V muffin fan #273-241 that's the right
size. $25 is much better than $75.

The original fan is 220V. I can wire up the new fan as 120V, but what
would really be great is if I could wire it up as 240V. That'd move a
whole lot more air.

Will the fan be able to deal with the higher voltage?

Radio Shack 273-241 is rated at 120V, 22W (approx 180mA)

You could wire a 4uF (or close) MKP motor start cap in series with the
fan. At 60 Hz this should give about 660 ohms series reactance which
should drop 120V at 180mA if my arithmetic is correct.
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Whether the capacitor idea would work or not depends on the type of motor.
If it is induction, you could end up with well over rated voltage on the fan
due to resonance. definitely not a good idea with inductive devices. Also
the power being 22 watts doesn't necessarily mean that the current is
0.18A -it could be more because of power factor.
The motor could be shaded pole induction or possibly brushless DC. I expect
that the original was shaded pole. What the radio shack one is is unknown-
and its ruggedness in the particular application is questionable.

Unfortunately the best solution is simply to bite the bullet and replace the
fan with a 240V model.
try
http://www.surplussales.com/Fans-Blo...ansBlow-3.html

Don Kelly
remove the X to answer



I have used this method with low powered ac fans usually as a cheap
way of running them at less than maximum speed and I have not noticed
any exccessive heating of the motor.