MIG welding with DC power supplies

YOu will need a higher voltage than 14 volts. 25 volts or more.

John

OK... If I put two of them in series, I could get 100 amps at 28 volts. Would that be good enough for welding most stuff. I hope that I am making sense, I am a little drunk at the moment (wife bday)

"Ignoramus2596" wrote: (clip)I think that they are CC

^^^^^^^^^^^^^^^^ Isn't that what you would use for stick? I think you want constant voltage for MIG.

Leo, I am sorry, I was and still am a little drunk, I meant to say CV.

If you put the two in series you will have the combined voltages but the current capacity of the smaller one.

Sure. They can do 100 amps at 14v. So, two of them could produce 100 amps at 28 volts, if put in series. That, I suspect, is not so bad for MIG welding.

Their current meters show a red area above 100 amps, so, I think, they could possibly go higher at reduced duty cycle.

The grounding arrangements on these might screw you over. unless the units wind up truly floating related to each other they couldnt be rigged up in series without causing then instant smoke and crack of the ic's rupturing on the 100A dead short

I think it will have issues trying to gang both PSU's together without using a LOT of protection to keep the business end of the PSU apart.

Because they are voltage and current sources they wont be as simple as hooking up 2 batteries (Voltage source only) and likely one mistake and you will be faced with 2 power supplies making smoke.

but have fun with it I'd have to look to find 3 computer PSU's for that little so its not like youre really out on the parts cost.

Nothin to lose but your eyebrows

You're probably going to want 22 to 28 volts. 100 amps is enough for thin metal, maybe up to 1/8" with fluxcore. However, if they have foldback current limiting they'll trip out when the wire touches the work.

Just a word of warning - remember the supplies might not work stacked. Most will. But make sure there is not a problem early on.

I don't see much voltage isolation issue - being so low, but there might be internal circuits that don't like it.

Martin

Martin Eastburn @ home at Lions' Lair with our computer lionslair at consolidated dot net NRA LOH & Endowment Member NRA Second Amendment Task Force Charter Founder

Ignoramus20905 wrote:

Now is a great time to go experiment!

Yes, the cost is negligible, but getting rid of smoke smelling hunks of metal is not as much fun.

Replying to another poster, I will see when I get them, but their output relinking arrangement makes me hope that DC output is isolated. (as is usually the case) With that, putting them in series should be possible.

Thanks. If their DC output is isolated from ground, then, I hope, I can put them in series instead and switch them to 100A, 14V outputs. In series of two, that would give me 100A, 28 volts. As they seem to be able to go beyond

That would be unfortunate.

The manual for them is here:

also:

``The reference circuit maintains a constant voltage to the load as the load conditions vary. The reference circuit consists of reactor L4, transformer T3, bridge rectifier CR3, variable resistor R4, filter choke L3, and magnetic amplifier T2. The input ac voltage is applied to transformer T3. During each half-cycle of the ac voltage appearing across transformer T3 secon- dary, two diodes in bridge rectifier CR3 conduct in series and produce a direct current (dc) pulsw in the output. During the second half-cycle of the ac voltage that appears across transformer T3 secondary, the two other diodes in bridge rectifier CR3 conduct in series, and produce another dc output pulse in the same direction. These dc pulses are then applied as reference voltage to the saturation control winding (ter- minals 5 and 6) of magnetic amplifier T2. Variable resistor R4 adjusts the output of bridge rectifier CR3.''

So, it seems to my uneducated eye that they do not have foldback current limiting, or really much current limiting at all. There is a breaker CB1(A,B) though. (on the top left, on the AC power line side)

Good point. See my reply to Don, with a pointer to the schematic. It does not seem that any output is connected to ground.

It's made to work with both 14V and 24 volts, so, I think, 28 volts will not hurt it.

Don,

The complete manual is here:

As long as you don't get any oscillation in the mag amp. it should work fine. The unit has voltage regulation and also you can vary the output voltage which is necessary to vary the heat of the welding process.

John

Thanks John. Three of them, two in series and one in parallel (with an appropriate diode to prevent "backflow" of current), could make a

and even better one is here