AC vs DC Equivalent Amperage?

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Personally I have two DC welders, a lincoln 180 and a hobart champ stick welder.  I don't have any experience with AC myself.  My question is - is 140 DC equivalent to 140 AC?  I know with DC you have DCEN and DCEP which can give you greater penetration.I don't think I need anything larger then my lincoln for what I do but I've been trying to understand the difference in this regard.Thank you,Matt
Reply:With regards to penetrating, the simple answer it's no. The DCEP portion of an equal amplitude 50%-time-balanced AC waveform puts less heat into a joint than the DCEN portion, which is part of the reason you almost always need more amperage when welding in AC.  But then again, my mind is always in TIG mode, so I'm sure someone else will chime in Last edited by Oscar; 10-19-2014 at 09:59 AM. 1st on WeldingWeb to have a scrolling sig! HTP Invertig 400HTP Invertig 221HTP ProPulse 300HTP ProPulse 200 x2HTP ProPulse 220MTSHTP Inverarc 200TLP HTP Microcut 875SC
Reply:Originally Posted by OscarWith regards to penetrating, the simple answer it's no. The DCEP portion of an equal amplitude 50%-time-balanced AC waveform puts less heat into a joint than the DCEN portion, which is part of the reason you almost always need more amperage when welding in AC.  But then again, my mind is always in TIG mode, so I'm sure someone else will chime in
Reply:Originally Posted by MinnesotaDaveTrue only for tig Oscar.  With stick, DCEP has more penetration.Since AC is a balance of the two, a little more amps would be required for the same penetration.
Reply:Originally Posted by Willie BI'm counting on you teacher. Why? It happens, I know. I don't understand why. DCEP flows electrons from work to rod sending more heat to rod, melting the rod faster. Why does it penetrate deeper? Welding thin steel with 6013 I use DCEN for less burn through, why?
Reply:Originally Posted by Willie BI'm counting on you teacher. Why? It happens, I know. I don't understand why. DCEP flows electrons from work to rod sending more heat to rod, melting the rod faster. Why does it penetrate deeper? Welding thin steel with 6013 I use DCEN for less burn through, why?
Reply:In reverse polarity DCEP  DC stick SMAW which is the most common polarity, electrons flow from the work to the electrode. In TIG principals, this melts the electrode, overheats the torch, provides lots of cleaning action in non ferrous metals, but because of lots of heat at the tungsten and little at the work, it isn't practical in TIG. In stick, it is common. Logic says this should produce quick metal deposition, yet logic doesn't explain that molten metal jumping like a salmon in a fish ladder against the electron current to penetrate deeply into the joint. I've seen diagrams showing electrons flowing one direction, ions flowing the opposite direction. Might it be ions from the rod carrying droplets of liquid steel to the work?Logic again says DCEP overhead welding shouldn't work. Liquid steel should fall away from the joint instead of defying gravity and jumping to the joint.Inquiring minds want to know.
Reply:Originally Posted by Willie BLogic again says DCEP overhead welding shouldn't work. Liquid steel should fall away from the joint instead of defying gravity and jumping to the joint.Inquiring minds want to know.
Reply:Wow - that's a lot of info.  So from what I gather then - If I am understanding correctly - AC requires more amperage then DC SMAW.How much - I'm not sure, it would depend if we were talking DCEN or DCEP.Is that correct?Thanks,Matt
Reply:It's not much, maybe 10% or so.Dave J.Beware of false knowledge; it is more dangerous than ignorance. ~George Bernard Shaw~ Syncro 350Invertec v250-sThermal Arc 161 and 300MM210DialarcTried being normal once, didn't take....I think it was a Tuesday.
Reply:Since I grossly over built the DC side of my 230 amp craftsman I have some DC settings available to me that other welding machines just don't offer.My favorite DC setting for 7024 is what I call rough DC. Its "rough" because it gets used straight off the rectifier with no inductive choke. Normally you never want to do this with a OEM machine and rectifier. I don't have A single rectifier, I opted for a rectifier array. One big advantage this gives me is full rated AC amps in DC. Only major draw back is you have to use AC compatible rods.I would have to say that rough DC at 180 to 190 amps penetrates about like AC running at 230 amps. Not only does it penetrate better, but the electrode is also consumed a little faster.So running rough DC is just more efficient.old Miller spectrum 625 Lincoln SP-135 T, CO2+0.025 wireMiller model 250 and WP-18V torchCraftsman 100amp AC/DC and WP-17V torchCentury 115-004 HF arc stabilizerHome made 4 transformer spot welderHome made alternator welder
Reply:Thank you all for the great information.Matt