Power from voltage

[pointer2null]

Can you calculate the current from measuring the open circuit voltage on a MIG?

 

[Archie]

Well yes and no. Yes, current is related to voltage very simply by V=IR. However, the resistance R is dependent on all manner of variables such as arc length etc so for a given voltage the current could be within quite a range. This is why when manufacturers quote a current range for a machine it has been worked out with a load bank so that standard results are obtained. I think Jake SS said that's how it was done a while back.

 

[Hitch]

I dont believe so, factors such as arc length, wire speed, are all factors that can alter the current.

One way is to use one of those clamp on ammeters, and run a bead. The sort that just clip over the cable, no direct contact is required.

 

[rtbcomp]

I........One way is to use one of those clamp on ammeters, and run a bead. The sort that just clip over the cable, no direct contact is required.

Make sure you get a DC one though, the cheap & cheerful ones are AC only.

 

[R Kraft]

Can you calculate the current from measuring the open circuit voltage on a MIG?

The ratings in the manual or the front panel seem to be accurate enough for most work.
Why did you need to know ?
Robert

 

[pointer2null]

Manual? One of them would be nice, but this machine has been obsolete for 15 years! All I have is the dial in the front numbered 1 - 6 and the panel at the back that tells me the max output and duty cycle.

It's more out of curiosity than any actual need.

 

[shenion]

Many panels also tell the minimum current.

To measure the voltage, you would need an RMS meter and also provide a load. Then you could guess the current range from the voltage given the gas and wire size.

If it goes down to 18V or less, then it should be ok for thin metal.