how to check voltage output on a mig?

# Thread: how to check voltage output on a mig?

Join Date
Oct 2009
Location
Germany
Posts
203

## how to check voltage output on a mig?

I would like to know what the voltage is at the different settings on my mig welder. It has a six step switch. Or am I stating it wrong. I am under the understanding that the switch selects the voltage and the wire feed speed control the amperage, correct? I am amazed at how little I turn the WFS and it affects how it welds. The manual does not list the voltages.
It is connected to 400 volts single phase. It is only a 200 amp unit.

2. WeldingWeb Apprentice
Join Date
Nov 2009
Posts
21

## Re: how to check voltage output on a mig?

Hey Burnandreturn!

You can easily check the voltage of your machine while welding with a standard DC Voltmeter. I assume this is an all-in-one MIG unit. You want to measure the voltage with the lead's connected to weld power connection at the back if the weld gun, and the ground/workpiece you are welding on. Make sure the DC volt range can accomodate up to 100V (realistically if it has a 50V setting you are fine). You are correct in your voltage and amerage assumptions. The only other variable that you need to take into consideration is the "Stick-out", which is basically the distance from the mig tip to the work piece (for all the theriost's out there, we are talking simple explanations here). You can do a lot of experimination with a simple volt meter and clamp on ammeter to help understand the theory's behind welding and what the different variables (settings) do to affect your weld.

Have fun, but do it safely! An extra set of hands and eyes works best for this type of "work".

3. WeldingWeb Craftsman
Join Date
Jun 2009
Posts
1,524

## Re: how to check voltage output on a mig?

Wow, that’s a tall order. Ok, with out going off the deep end I’ll try to explain it as simply as possible.
The welding power supply is divided in two half’s, an input side [400 volts] and the output side [200 amps]. In-between the two is a transformer that has many turns of wire connected to the input voltage source and a fewer turns of wire connected to the output for welding. Both coils of wire are wound around an iron core and both coils are not electrically connected. The ratio of the turns of the coils determines the output voltage given the input voltage.
For a turns ratio of 13 the output voltage is 400/13 = 30.7 volts. You say that the welder has six power settings, that means that the input coil is divided into six segments with six different turns ratios. Each ratio is successively higher say, 15, 19, 20, 22, 24, making the output lower with each step.
Now things get a bit more complex, the AC output of 30.7 volts is rectified to DC voltage and storied in a capacitor. The capacitor is charged to the maximum of the rectified voltage, 1.41 x 30.7 = 43.287volts, this also holds true for the other heat setting voltages. This is the OPEN CIRCUIT voltage when not welding. The voltage while welding will drop to 12 to 26 volts depending on the heat switch, wire speed and wire diameter settings. Typically you would measure the voltage from the ground clamp to the arc. However, measuring the arc voltage is very difficult. The next best place to measure the voltage is from the ground clamp to the wire contact tip. The error missing the arc voltage will be small.
Knowing the voltage doesn’t have much use. The voltage [heat] is usually posted on a chart for the stock thickness and type of wire. The wire speed may also be posted on the same chart, it may also be calculated. These values are all recommended settings and will most likely be tweaked for the task at hand.

Join Date
Oct 2009
Location
Germany
Posts
203

## Re: how to check voltage output on a mig?

Wow, much more complicated than I thought it would be! I think I should just weld with it in all positions on different thickness material and get an idea of what works. I have always welded with stick and this mig is testing me some. But it gets better. thank you for the help.

5. Master Welder
Join Date
Jan 2004
Location
Northern Cal., Shasta County
Posts
7,990

## Re: how to check voltage output on a mig?

Originally Posted by burnandreturn
Wow, much more complicated than I thought it would be! I think I should just weld with it in all positions on different thickness material and get an idea of what works. I have always welded with stick and this mig is testing me some. But it gets better. thank you for the help.
Actually it doesn't need to be complicated. You can make it complicated sure, but not for what you really want. Highlandwelder 'splained it about as good as any. There are numerous things that can have sublte effects at any given time but but those things tend to average themselves out. And that's what you're looking for, average operating parameters for a given tap. No need to get all hung up about whether you're measuring at the machine end or stinger end for something that's constantly varying at this point. No need to get worried about whether the input is a volt higher today than yeasterday. That stuff all averages out over the years time.