HOW DOES AC WELDING DIFFER FROM DC WELDING

[stuckmotor]

Thanks Shield Arc. I guess I was wrong.

 

[Shield Arc]

Thanks Shield Arc. I guess I was wrong.

You are welcome!
I've done it since I started out, at 14-years old.

 

[stuckmotor]

Shield Arc,
Would you do it with an AC welder? That's all I have.

 

[k0ua]

Well I'm no pro, but that's how I've been doing it for years.

And I know I am not a pro, and I hold the electrode to get started too.

 

[buickanddeere]

AC current starts and stops 120 times per second . DC is continuous .

 

[k0ua]

Shield Arc,
Would you do it with an AC welder? That's all I have.

Some things to keep in mind. When your skin is wet, your gloves soaked thru, be CAREFUL!. If you don't have to weld, consider doing it some other time. If you have to, try real hard not to "complete the circuit". In other words, don't touch both sides of circuit at the same time. Don't lean on that bush hog and touch the electrode at the same time. The OCV (Open Circuit Voltage) measured between ground and stinger is not supposed to be over 80 volts, but 80 volts is enough to knock your **** stiff if you are wet.

On a dry fall day you could touch both stinger and ground and probably never feel it, depending on how calloused your hands are. Of course if you just touch ground and never touch the stinger, no current will flow thru your body. Also if you just touch the stinger and not the ground clamp, or the weldment, then no current will flow thru your body either.

Welding is just like working around any other source of electricity, the thing that needs to be foremost in your mind is "don't become part of the circuit". When I touch an electrode to steady it when striking the arc, I make it a point to not be touching the grounded workpiece. I also make it a point to not have wet gloves or wet skin. Dry calloused skin has a high resistance to the flow of current, but wet skin has a very low resistance to the flow of current.

Also keep in mind that a welders source of current is not very current limited from the point of view of the human tolerance to current flowing across the body. They tell us that at as little as 50 milliamps is enough to kill you. That is 50 thousandths of 1 amp. We often set our welder to deliver over 100 amps. That is thousands of times more than what is needed to kill us.

 

[Soundguy]

lol, I think our terminology is getting confused, caps don't fill holes ( as in a zero volt reference and up ) they smooth out " ripples"/"noise" of a specific voltage and are also used as storage cells. .

Your the confused one!

what you are calling filling a hole, as in the space between the crests of the positive wave form as compaired to steady state dc.. and YES, caps will smooth / filter that bumpy DC to steady state DC .

 

[Soundguy]

lol, I think our terminology is getting confused, caps don't fill holes ( as in a zero volt reference and up ) they smooth out " ripples"/"noise" of a specific voltage and are also used as storage cells. .

here, this might help. and for the other EE's out there, this drawing is OBVIOUSLY not scaled.. freq, etc, waveform errors, etc. it's just a pictogram.

Skyhook... the first line shows half wave dc, an ac wave form ran thru a diode and it chops one half off as the diode oposes current flow in one direction.

the next line shows full wave dc, either a transformer and 2 diodes, or 4 diodes aranges so that the lower waveform is tossed 'up top'.. this makes for a riple-dc.

Now, if you take a capacitor and put across the ground reference and the positive test point. the capacitor will 'fill in' the space between those waveforms. ( of course you must have a large enough cap to filter with... loaded or unloaded circuit will effect that, yada yada..

the third line shows the full wave dc with a steady state line over it and a green hash shaded area.. that's what the cap is doing, the green shaded area.

to your vom, the 4 line is what gets reported... steady state dc.

 

[k0ua]

View attachment 456660


here, this might help. and for the other EE's out there, this drawing is OBVIOUSLY not scaled.. freq, etc, waveform errors, etc. it's just a pictogram.

Skyhook... the first line shows half wave dc, an ac wave form ran thru a diode and it chops one half off as the diode oposes current flow in one direction.

the next line shows full wave dc, either a transformer and 2 diodes, or 4 diodes aranges so that the lower waveform is tossed 'up top'.. this makes for a riple-dc.

Now, if you take a capacitor and put across the ground reference and the positive test point. the capacitor will 'fill in' the space between those waveforms. ( of course you must have a large enough cap to filter with... loaded or unloaded circuit will effect that, yada yada..

the third line shows the full wave dc with a steady state line over it and a green hash shaded area.. that's what the cap is doing, the green shaded area.

to your vom, the 4 line is what gets reported... steady state dc.

I considered doing this drawing, but I was lazy. I am glad you posted it.

 

[Soundguy]

I considered doing this drawing, but I was lazy. I am glad you posted it.

I realize it's hard for those that are not engineers or tech's to visualize some of these concepts, and how cap's and inductors interact with circuits voltage and current, etc.

hopefully the drawing will help. it's a bad drawing, but i think it will work. the signal 'generator' ( my hand ) needs to be calibrated.

 

[k0ua]

I realize it's hard for those that are not engineers or tech's to visualize some of these concepts, and how cap's and inductors interact with circuits voltage and current, etc.

hopefully the drawing will help. it's a bad drawing, but i think it will work. the signal 'generator' ( my hand ) needs to be calibrated.

Actually I though your waveforms were not bad at all. I don't believe I could have done any better.

It all seems so simple for those of us that have been around these concepts for decades, but to many here it is all new concepts. Nothing wrong with that, as I am sure that the fields of endeavor that they work in seem simple to them too, and I would likely not have a clue about their work. I have started off into a new tangent of learning about health insurance in my advancing years, and leaving engineering behind.

Imagine my confusion and questions when I first jumped into this field. But hey, I am a professional now.

 

[FTG-05]

So, if I may ask: What's a good entry level DC welder? Something that's usable for typical farm equipment. I already have a Lincoln SP-175 Plus MIG, but I need something with a little more oomph for 3/8" and up material.

I looked at the old Lincoln AC/DC buzz box, but DC amps are only 125. Doesn't sound like enough.

Thanks,

 

[k0ua]

So, if I may ask: What's a good entry level DC welder? Something that's usable for typical farm equipment. I already have a Lincoln SP-175 Plus MIG, but I need something with a little more oomph for 3/8" and up material.

I looked at the old Lincoln AC/DC buzz box, but DC amps are only 125. Doesn't sound like enough.

Thanks,

Everlast Power Arc 200ST. Contact Mark on this forum for a TBN discount.

 

[paulsharvey]

So, if I may ask: What's a good entry level DC welder? Something that's usable for typical farm equipment. I already have a Lincoln SP-175 Plus MIG, but I need something with a little more oomph for 3/8" and up material.

I looked at the old Lincoln AC/DC buzz box, but DC amps are only 125. Doesn't sound like enough.

Thanks,

The 125 amps DC would be fine, but I wouldn't spend "new" price for the AC/DC; think they are around $385-400 and there's plenty of options when you get in that range. I quick Google search returned $400-550; so I wouldn't pay that for one.

Edit: Hobart Stockdale LX235 is 150 amps DC/225 AC; for same price (at northern tool, new)

 

[sd455dan]

So, if I may ask: What's a good entry level DC welder? Something that's usable for typical farm equipment. I already have a Lincoln SP-175 Plus MIG, but I need something with a little more oomph for 3/8" and up material.

I looked at the old Lincoln AC/DC buzz box, but DC amps are only 125. Doesn't sound like enough.

Thanks,

The everlast would be really nice for sure- If you have the coin
but on a tight budget Craigslist, at least what i see every week lots of great ac/dc transformer welders for $50- $200 most come with leads to which are worth at least $50.

 

[k0ua]

My little Everlast PA160 has done all that I have needed done. I paid $265 several years ago for it. I use it for TIG too.

 

[Shield Arc]

Shield Arc,
Would you do it with an AC welder? That's all I have.

Sure! But with good welding gloves on. Back when I was working I welded a lot with just White Ox cotton gloves. Used those gloves mostly for rigging, but they worked OK for a few quick welds.

 

[FTG-05]

Everlast Power Arc 200ST. Contact Mark on this forum for a TBN discount.

Looking at the specs as we speak, thanks!!!

:beer:

 

[k0ua]

Looking at the specs as we speak, thanks!!!

:beer:

Ask Shield Arc about how he likes his. I can't remember how much the TBN discount from Mark at Everlast was, but it was a fair chunk. Send him a PM

 

[Shield Arc]

Looking at the specs as we speak, thanks!!!

The PowerArc 200ST really likes ESAB's 10P-Plus 6010.