MIG amperage

[automech]

from another site: Welding machines are usually classified as constant current (CC) or constant voltage (CV); a constant current machine varies its output voltage to maintain a steady current while a constant voltage machine will fluctuate its output current to maintain a set voltage. Shielded metal arc welding will use a constant current source and gas metal arc welding and flux-cored arc welding typically use constant voltage sources but constant current is also possible with a voltage sensing wire feeder.

The nature of the CV machine is required by gas metal arc welding and flux-cored arc welding because the welder is not able to control the arc length manually. If a welder attempted to use a CV machine to weld with shielded metal arc welding the small fluctuations in the arc distance would cause wide fluctuations in the machine's output. With a CC machine the welder can count on a fixed number of amps reaching the material to be welded regardless of the arc distance but too much distance will cause poor welding.

 

[J_J]

I found this.

 

[jake98]

I found this.

Those two charts together give good info, thanks JJ, I bookmarked them.

 

[Mark @ Everlast]

Mig process is typically a Constant voltage process. The taps (detents) are preset voltage levels. Some welders have a lot more taps, with ranges to provide more selections. Other welders such as inverters allow you to change the Voltage infinitely. Once set, the voltage is held constant while welding (theoretically).

Wire speed and amps are directly linked. Increasing wire speed automatically delivers more amps. Some mig welders have an scale for amps...Others for wire speed, but they do the same thing. The faster the wire feeds, the higher the amps go.

 

[dstig1]

Perhaps this will help. Admittedly I'm shooting out my butt on this, but it follows basic electrical theory...sort of... I know I'm going to get flayed for this, but I'll try to make some sort of layman sense out of it. No I'm not an EE, but I stayed at a Holiday Inn Express last night

1. It's a CV source, so it tries to maintain the voltage at the setting.
2. Every time you short the wire to the work as it feeds out, the voltage wants to drop as there is less resistance when it shorts than when it is holding an arc across a gap.
3. Since it tries to keep the voltage constant, it will boost the power to keep V constant.
4. Since V is held constant, A must increase and the wire melts back a bit.
5. The faster the wire moves, the more often this must happen, thus the higher amp draw on average.

Anyone agree with me? Maybe I got that wrong, but on a Fri night, it sounds good

 

[k0ua]

Perhaps this will help. Admittedly I'm shooting out my butt on this, but it follows basic electrical theory...sort of... I know I'm going to get flayed for this, but I'll try to make some sort of layman sense out of it. No I'm not an EE, but I stayed at a Holiday Inn Express last night

1. It's a CV source, so it tries to maintain the voltage at the setting.
2. Every time you short the wire to the work as it feeds out, the voltage wants to drop as there is less resistance when it shorts than when it is holding an arc across a gap.
3. Since it tries to keep the voltage constant, it will boost the power to keep V constant.
4. Since V is held constant, A must increase and the wire melts back a bit.
5. The faster the wire moves, the more often this must happen, thus the higher amp draw on average.

Anyone agree with me? Maybe I got that wrong, but on a Fri night, it sounds good

I am buying into it.. I am not a EE either, nor do I play one on TV, but it sounds about right to me.

James K0UA

 

[henryswe]

Just to make more variables the larger diameter the wire the, more current. I also started mixing my gases and found other characteristics. I just used 2 flow meters to mix gas.

 

[Shield Arc]

Wire speed and amps are directly linked. Increasing wire speed automatically delivers more amps.

That doesn't work with this combination! Turn the wire speed up with this setup, and the wire will bang into the puddle!

 

[Mark @ Everlast]

Well voltage sensing wire feeding excepted.

 

[J_J]

My best guess is that some machines have taps for different voltage, the there is an open voltage, and current drawing voltage, and even that is variable within a narrow range, based on the air gap between the wire and the puddle.