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Old 11-10-13, 11:39 AM   #1
oil pan 4
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Join Date: Nov 2012
Location: NM
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Default Eco mod my welder

I picked up a craftsman 230 amp AC welder for $100. It was in rough shape.
One thing I do not like about its rated for a .77 power factor.

This means that it draws around 11,000 Volt Amps of reactive or apparent power for this highly reactive inductive load. That is 50 amps of 220.
It draws 8.6kw of true power.

If the power factor was corrected to closer to 1 it would only draw 39 amps.

I figure if a few high voltage non polarized capacitors can knock 11 amps (of 220!) off the reactive load. How can I not do this?

Aside from saving 11 amps of utility power I would like to be able to run this off grid on a generator and I don't want to screw up the power for any other items being run off the generator. Also saving 11 amps of 220 when you are on a generator is very valuable.

Only problem is I am having trouble with the math that you use to figure out how much capacitor you need to correct power factor.

I think it will take 3 or four 100uf motor run capacitors to fully correct the P.F. when running the welder at full power. Or more I really don't know for sure.

Only thing I can think of is run it through my kill-a-watt meter, up to 20 amps and check the P.F. with and with out capacitors and then wing it with an amp clamp only from there on. If I get the power factor corrected it should read closer to 40 amps, if not then closer to 50 amps.

Then once I get this power factor thing straightened out I am going to convert it to DC.

The difference between an 0.8 power factor and a power factor of 1 means the engine has to work up to 27% harder to drive the generator.
On a generator you may not have the horsepower to do that.


Last edited by oil pan 4; 05-17-16 at 10:38 PM..
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