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  • An Amp is an Amp

    An amp is an amp or is it? Hi all. I'm having a tough time figuring out if say a mig is delivering 125 amps through .030-.035" wire and a tombstone dc arc welder is delivering 125 amps through a 3/32-1/8" rod, is it the same thing???

    After all each is delivering 125 amps but one is able to do it through a much thicker medium, so is it actually hotter?

    In addition to this is an AC welder delivering 225 amps the same as a DC welder delivering say 112 amps? If not why do most A/C -D/C machines seem to halve the D/C value? Why don't they both supply 225 amps in both A/C and D/C?

    Just a few things I have been pondering, who's got the answers, if there are any? Uncrichie.

  • #2
    Hey Uncrichie - I asked the same question a while ago and got the answer I was looking for:

    http://www.hobartwelders.com/weldtal...ad.php?t=26870
    Pete

    While mere mortals get their recommended daily allowance of iron from a pill - Weldors will take it Cold Rolled or DOM, thank you very much!

    www.texhand.com

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    • #3
      The AC/DC and AC only arc welders typically have a high and a low output tap. The DC output uses the low tap. This cuts down the max current. I believe this is done to prevent overheating of the transformer but have never seen that in writing. Some transformers are designed for rectifier duty as used in DC power supplies.
      What do I know I am just an electronics technician.

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      • #4
        After all each is delivering 125 amps but one is able to do it through a much thicker medium, so is it actually hotter?
        There is also the load voltage to take into consideration, if the amperage remains equal.

        100 amps at 100 volts would put a lot more energy/heat into a hypothetical weldment than 100 amps at 1 volt. Numbers exaggerated of course.

        Comment


        • #5
          amp is an amp yes no

          Howdy Howdy!

          An amp is an amp, so long as the voltage is the same, to keep apples to apples. The term should really be a watt is a watt. a watt is amp x volt. a watt is a measure of how much work can be done. I think you'd get a better feal for comparing machines to one another if the machines labels used a max watt rating. like on small machines, 90 amps at 18 volts, and = 1620 watts. 90 amps x 20 volts = 1800 watts. thats a 10% difference with no difference on the label in regards to amps. not really pertaining to your question.

          Another thing to think of, is not just the metal thickness. i.e. wire dia to rod dia. One must also consider the ionized gas in which the arc creates, and the metal transfer within the arc. Solid wire behaves differently with shielding gas, then a stick electrode with flux coating. It's kindof a physics/chemical thing. One morething is speed at which the metal is fed into the arc. comparing wire to sticks are kinda like apples and oranges.

          maybee this helps a little. Brian Lee Sparkeee29

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          • #6
            This is perhaps informative: http://www.thefabricator.com/Aluminu...cle.cfm?ID=613
            --- RJL ----------------------------------------------

            Ordinarily I'm insane, but I have lucid moments when I'm merely stupid.
            -------------------------

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            • #7
              An amp is an amp, but you can vary the welding characteristics of those amps drastically by running them thru different consumables using different process'.

              An example would be: say you have 200 amps at your disposal, run them thru a 6010 stick rod and you end up with a forcefull arc with lots of dig and a moderate amount of deposition. Run them thru a 7018 stick rod and you have a moderate amount of penetration and more deposition. Run them thru one of the jet rods and you have a minimum of penetration (admixture) and even more deposition.

              Same with the different wire process' and even different wires in the same process. those 200 amps will produce much more penetration using a flux core wire over using a solid wire. And will deposit more (flat) using say a
              NS-3M wire than any other.

              But out of position you'll get maximum deposition (assuming you're not out in the wind) out of a dual shield type wire.
              All using the those same 200 amps.

              So it becomes a matter of using the right process and the right consumable within that process to get the most bang for the buck in your particular welding application and the enviroment the welds are made in. Fortunes have been made, and lost, based on these decisions

              JTMcC.

              Comment


              • #8
                Also, consider that with MIG, you have constant voltage and with STICK you have constant current...so you're also dealing with a curve..not to complicate the question.

                Comment


                • #9
                  Hi, Uncle!

                  Yer runnin' yer motor for little result!

                  I feel for ya. Been there, done that! I agonized over the same things for a long time untill the brethren convinced me that the really important part is how the weld turned out.

                  The definition of an "amp" (ampere) is "one coulomb of electrons passing a given point in one second".

                  Like JtMcC said, it's how you manage them coulombs........

                  Hank
                  ...from the Gadget Garage
                  MM 210 w/3035, BWE
                  HH 210 w/DP 3035
                  TA185TSW
                  Victor O/A "J" series, SuperRange
                  Avatar courtesy of Bob Sigmon...

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                  • #10
                    Originally posted by hankj View Post
                    The definition of an "amp" (ampere) is "one coulomb of electrons passing a given point in one second".
                    Hank

                    OH! Well now...that sure simplified it all for me!!!.........

                    Comment


                    • #11
                      Originally posted by Sully2 View Post

                      Originally posted by hankj View Post
                      The definition of an "amp" (ampere) is "one coulomb of electrons passing a given point in one second".


                      Hank
                      OH! Well now...that sure simplified it all for me!!!.........
                      Maybe this'll help:

                      One coulomb is defined as one farad of capacitance times one volt of electric potential difference.
                      Pete

                      While mere mortals get their recommended daily allowance of iron from a pill - Weldors will take it Cold Rolled or DOM, thank you very much!

                      www.texhand.com

                      Comment


                      • #12
                        How fast are the electrons running if there are 6.241506 x 10^18 electrons running past that point in one second?
                        --- RJL ----------------------------------------------

                        Ordinarily I'm insane, but I have lucid moments when I'm merely stupid.
                        -------------------------

                        Comment


                        • #13
                          Originally posted by usmcpop View Post
                          How fast are the electrons running if there are 6.241506 x 10^18 electrons running past that point in one second?
                          Are we going to get into the woodchuck / firewood scale soon? Cuz I KNOW that one!
                          I NEED MORE COWBELL!!!


                          'Red' Powcon 300ST (no torch yet)
                          (ok, not really a 'Red'... )
                          'Blue' Miller 35 (older than me and runs great), Thunderbolt AC arc (ditto)
                          'Craftsman' AC arc (who made this originally?)
                          O/A x 2 (both smaller than I'd like)
                          14" Milwaukee chopper
                          20t HF press (crap, but works)
                          Buffalo forge w/ blower
                          Alot of pumps!

                          "All of us know more than any of us."- TexHand

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                          • #14
                            Originally posted by usmcpop View Post
                            How fast are the electrons running if there are 6.241506 x 10^18 electrons running past that point in one second?
                            A couple meters per second maximum in a conductor. Usually slower. There are a LOT of electrons available to move.

                            Assuming one electron per atom is available for conduction in copper: There are approximately 6*10^23 atoms per mole, so there are about 10^5 coulombs per 7cm^3 (molar volume of Cu). 16Ga wire is about 0.006cm^2 cross section, so a length about 170cm is one cm^3, and a length of about 1.2m is one mole. So, one amp flowing through 16Ga wire has an average velocity of (1.2m/10^5C)*(1C/s) gives a velocity of 0.012mm/s. This is an average. Each electron is actually generally moving a good bit faster than this, but doesn't move straight.
                            I may not be good looking, but I make up for it with my dazzling lack of personality

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                            • #15
                              This thread just gave me a headache
                              Pete

                              While mere mortals get their recommended daily allowance of iron from a pill - Weldors will take it Cold Rolled or DOM, thank you very much!

                              www.texhand.com

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