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running 120V muffin fan on 240V

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?
 
J

Jack

Jan 1, 1970
0
Although it may be possible to run the 120 fan motor on 220 without damaging
it, you would be wrong to think that you would get a lot more airflow
because the speed of an induction motor is primarily a function of the
frequency of the power source, not the voltage. Typical induction motors
run at only slightly less than the synchronous speed - for example 1725 rpm
vs 1800 rpm synchronous. You might get this up to 1760 by running it at 220
but it's not going to double or anything close to double.
 
P

PeterD

Jan 1, 1970
0
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.

Only great for a few seconds... said:
That'd move a whole lot more air.

The speed (and therefore the air moving capabilities are probalby
based on teh fact it si a syncronous motor--fixed to the frequency of
the power, not the voltage.
Will the fan be able to deal with the higher voltage?

For a few seconds. If it is thermally protected, it might last a bit
longer but still not a good idea.

How about two fans in series?
 
R

Ross Herbert

Jan 1, 1970
0
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.
 
R

Ross Herbert

Jan 1, 1970
0
Radio Shack 273-241 is rated at 120V, 22W (approx 180mA)

You could wire a 4uF (or close) MKP ** MOTOR RUN ** 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.
 
J

Jack

Jan 1, 1970
0
I think if you do the analysis that you will find that adding the capacitor
in series will actually result in higher current in the motor than just
connecting it to the 220 directly.
The reactance of the capacitor will be 180 out of phase with the reactance
of the motor windings and so will exactly cancel it out and the current will
only be limited by the resistance of the motor windings -- the worst case
possible as far as overheating the motor goes.
Inserting a series resistance or another fan motor in series would be the
safest solution although I still don't think the motor would be damaged by
just connecting it directly.
 
J

jasen

Jan 1, 1970
0
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?

no. stack two of them and wire them in series,

or put a 240V AC rated capacitor of the aproprite size in series
with the fan to drop the voltage it sees to 120V,

or see if you can find a centre tap on the weldder's primary and hook
one end of the fan to that.

Bye.
Jasen
 
D

Don Kelly

Jan 1, 1970
0
----------------------------
Ross Herbert said:
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.
-------------
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-Blowers/FansBlow-3.html

Don Kelly [email protected]
remove the X to answer
 
R

Ross Herbert

Jan 1, 1970
0
----------------------------

-------------
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-Blowers/FansBlow-3.html

Don Kelly [email protected]
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.
 
J

Jack

Jan 1, 1970
0
Not really the same situation though is it Ross.

I guess mkirsch1 has taken the option of hooking his 120volt fan up to the
120volts available and left us all here spinning our wheels.
 
R

Ross Herbert

Jan 1, 1970
0
Not really the same situation though is it Ross.

I guess mkirsch1 has taken the option of hooking his 120volt fan up to the
120volts available and left us all here spinning our wheels.

No Jack, it isn't quite the same application, I agree. Nevertheless,
it would be worth a bit of experimentation to see just how well it
worked. If I had a 120Vac fan I would try it on our local 240Vac to
see how it worked in that role.

It would be nice if the OP would post to this group to let us know
what he is doing so we don't keep spinning our wheels.
 
D

Don Kelly

Jan 1, 1970
0
Ross Herbert said:
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.
 
R

Ross Herbert

Jan 1, 1970
0
Nope! Simple empirical method of testing - finger on motor frame.

If I took out my scope and took measurements the results would surely
have told me that the method was not advisable. Since it worked
without any problems I preferred to take this as a sign of its
effectiveness for the application.
 
D

Don Kelly

Jan 1, 1970
0
Ross Herbert said:
Nope! Simple empirical method of testing - finger on motor frame.

If I took out my scope and took measurements the results would surely
have told me that the method was not advisable. Since it worked
without any problems I preferred to take this as a sign of its
effectiveness for the application.
Fair enough (I wasn't thinking of a scope but a simple voltmeter) but as I
said- high R/X in the motor. --

Don Kelly [email protected]
remove the X to answer
----------------------------
 
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