DC Welding

[patrick_g]

Unless I'm reading it wrong, they do use a full wave rectifier.

Nothing wrong with your analysis, that is a full wave bridge circuit where the full voltage of the transformer secondary is expressed at the diodes rather than a two diode circuit with a center tapped secondary.

Pat

 

[Soundguy]

That appliction fee is why so many devices use a 'standard' ul listed wall wart xformer.. that is detachable.. and sold as a bundle.. vs building their own design.. too much payola to spread out over a sales life of an item..

Soundguy

Not that time. They gave me conditional approval, with the condition being to wrap a minimum of three layers of vinyl electrical tape over each insulated with nut.

The highest voltage was 120VAC +/- normal fluctuations. What boggles the mind is that the insulated wire nuts were UL approved. Why in H E double toothpicks did they want us to wrap insulation around a UL approved insulator approved for a much higher voltage? Like my customer said, they were probably justifying their existence. If they couldn't find something to gripe about then of course they weren't needed.

You ain't seen nuttin' till you design something that plugs into the wall AND attaches to a patient! I built a prototype hot/cold therapy machine for use on race horses and human athletes. VERY STRINGENT leakage standards and such. Hospital equipment standards make household UL approval look like a kindergarten game.

I remember various experiences with different peoples electric guitars and amps. You could get electrocuted!!!! Hard to be much more surprised than to close talk a microphone and get sparks between the mike and your lips!!!

Pat

 

[Soundguy]

I agree.. and it looks like the current is based on what tap they are using to feed the diode bridge.... etc..

Soundguy

Nothing wrong with your analysis, that is a full wave bridge circuit where the full voltage of the transformer secondary is expressed at the diodes rather than a two diode circuit with a center tapped secondary.

Pat

 

[Casey1]

A question to some that have that type of welder. Can you weld as large of stock with the 150 amp dc setting as the 225 amp ac in a single or equal passes.

 

[Brad_Blazer]

According to the "typical operating Procedures" in this document:
http://content.lincolnelectric.com/pdfs/products/literature/c210.pdf

DC runs at about 10% lower amps for a given electrode. I am guessing that would also apply to size of stock welded in a single pass. That would mean about 205 DC amps to equal 225AC.

 

[gunta]

The advantage is it welds much better,forget about ac,,just use dc,,if you don't know this than its hard to tell you much more,,,get you some 6010 rods and use dc,,elecrode positive,,but all rods will burn better on dcep,,,,thingy

 

[patrick_g]

The advantage is it welds much better,forget about ac,,just use dc,,if you don't know this than its hard to tell you much more,,,get you some 6010 rods and use dc,,elecrode positive,,but all rods will burn better on dcep,,,,thingy

Agreed, mostly. A reason to go AC on my Lincoln Tombstone is that you can get more heat at full power AC than you can get with full power DC. This is a RARE requirement for me (your needs may be different.) Within the heat available with DC it is typically superior.

Trivia questions for all you welding guys out there:

1. When do you want to use electrode negative (and why?)

2. The real welder dudes say straight and reverse polarity when referring to the polarity of the setup. Which is which? Is the rod + or is it - when using straight polarity?

Pat

 

[cp1969]

I am by no means a real welder but will take a shot at it.

Don't you use 'reverse' polarity (electrode positive) when you want the electrode to get most of the heat rather than the workpiece, such as when welding thin material?

 

[patrick_g]

I am by no means a real welder but will take a shot at it.

Don't you use 'reverse' polarity (electrode positive) when you want the electrode to get most of the heat rather than the workpiece, such as when welding thin material?

It is a plasma physics thing... Ions and such... You select the polarity to get the most heat at the work or the rod. One way gives more heat at the rod like if you want more fill material for the amount of heat/melting of the workpiece (thin workpiece is one reason) and the other way gives more heat/melting at the workpiece for the amount of rod used.

You have no choice with AC and that is yet another reason AC is not as good as DC.

DCSP (Direct Current Straight Polarity produces a narrow, deep weld. Since the heat is concentrated on the work, the welding process is more rapid and there is less distortion of the base metal. Usually, straight polarity is preferred over reverse polarity because you can achieve better welds. DCRP (reverse) makes a wider and more shallow weld and is not used as much. An exception is when it is aluminum. (something that nearly escapes me in practice)

Positive ions bombarding the workpiece tend to clean it and break through any oxide coating, an advantage for reverse. IT is sort of an advantage for AC since half of the tie the current is Reverse and so AC will weld rusty metal better than DC Straight Polarity (rod emitting electrons.)


The Weldor's Weld
by Sonia Balcer 8/21/82

Wherefore must I wear a mask when
I hold in my hand, the pen
wherewith I write poetry with fire?

How I long to discover the secrets that are hidden
in the theater before me;
to behold the movement of tiny, metal
particles, as they waltz and interlock
in a world within a world;
as they pirouette between the boundaries set
by the fire which frees them to move.

Oh, Lord in heaven! Why are not human eyes made
to see this wonder directly?
Must I always hold this dark glass before me?

Hark! He causes my heart, to see the mystery!
The metals are assaulted, by electric energy,
carried by heaving, heavy wires. In a molten flash,
I see the crystals breaking, and sighing;
the silent order of the solid surface, giving way
to rushing, hotly-radiant tides
that crash together like waves at a beach.

It swirls before me, an intricate dance
which I cannot see, but yet feel inside.

I delight to caress the molten piece
in my heart.
It is inside of me, and I am inside of it.
I slowly feel over and underneath
the hot liquid surfaces.
I move into its every contour, and through
the whole of it.

Bodies of metal, which once were separate;
the boundaries are fading.
It swirls and whirlpools within me-
It is all blurred now, caught
Into a quickly-freezing body of what once
was separate, but now is together,

a single piece.

Pat

 

[BTDT]

I didn't know anyone could get that "passionate" about welding. Well, maybe,, other,,, than gunta tin,,,,, (thingy),,,