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  • 3 Phase Needed to...???

    When I started shopping for a tig for aluminum. I was told a 250 amp tig would only ever be able to max out 225 amps using single phase current? Is this a true statement? I f so I would not bother with buying a 250 but instead perhaps a 225 or 200 amp tig. I primarily wish to weld crankcases on engines with it. Thanx Mike

  • #2
    First off the statement of a 250 Welder only outputting 225 on single phase may only apply to the specific unit they were selling.
    The reason for it is that when you are connected with 3 phase you have one third more power connected to it due to the third phase.

    Obviously you are looking at an inverter style unit if it will run on single or 3 phase and those do have advantages in portability if you need to weld away from home, you can run it on a good quality generator or a dryer outlet at a friends house. Carrying around a 3 phase generator or a rotary phase converter would be a bit more difficult.

    So next question is do you have a rotary phase converter and how big is it? I run a 350 AMP MIG welder on a 15 HP phase converter without any issues, at least with the stuff I weld.

    As far as welding crankcases. Are we talking car engine? aircraft engine? or smaller stuff? The first two do have rather thick areas that are going to require a lot of heat input to weld them. The smaller stuff not so much. IF you are looking at the big stuff, I am not sure that you don't want to be looking at a larger welder. If you look at the duty cycle of a welder it decreases as the output increases. If you are needing to run 200 plus amps and make long welds, you might look at a 300 amp welder so you are not fighting it. Remember that the imports (if that is what you are looking at) may be rated for a lot of amps, they are running the ragged edge when you turn them up that high.

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    • #3
      Thankyou for the reply. I will be building 3 cylinder snowmobile engines from 2 cylinder engines. I have a 100 amp econo tig by miller but...too light. I also bought a old oven for preheating and am finishing of a fixture and crank jig to hols all cases in alignment. I tinker around with engines a bit. I truly appreciate the Tips and Hints since I dont know too much thankyou Mike

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      • #4
        Powewr Feed!

        Oops I forgot I have a dedicated 50 amp circuit for my new TIG welder. Im still not sure I can run a 250 amp? three phase is NOT available to me. Thanx

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        • #5
          Originally posted by madman View Post
          ...I have a dedicated 50 amp circuit for my new TIG welder. Im still not sure I can run a 250 amp?...x
          50 amps is probably a little light for a 250 amp welder. Newer transformer welders can do "more with less" but would likely be pushing the limits
          with only 50 amps input. Inverters are a whole different story--we run our Dynasty 350 on a 50 amp circuit...
          Keith
          __________________________
          Just one project too many--that's what finally got him...

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          • #6
            You can run a 250 amp machine on a 50 amp breaker, just not at the full 250 amp rated output. I've got a synchrowave 350 running off a 60 amp breaker, but have yet to go 170/180 amps with it. The manual calls for a 120 amp breaker on 230 volts to get the full 350 out of it. I've been wanting to up the breaker, but the run wiring will be over taxed since I sized it for my mig needs way back when. Main thing to keep in mind is you can run a small breaker on big wires, but not vise versa. That's how fires start. Start pushing things like this with small breakers and it all becomes a balancing act...hotter the output, shorter the welds you can make at one time.

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            • #7
              I have an old (1980's or early 90's) Airco Heliwelder IV that is 300 amp. It's a transformer design unit and doesn't have the features like square wave and DC offset but it's still effective for what I need. Mind you I rarely turn it up more than 3/4 of full output but it's running on a 50 amp breaker and I am yet to pop the breaker running it.

              Now unit's like this old Airco, or an old Miller are single phase mostly and weld very well and have close to a 100% duty cycle. Heck the Airco has a 12 inch fan in the back for cooling. Mind you it's better than half the height of a full size refrigerator and just as wide, but they are also cheap and are a really good unit. Granted, if you are thinking you will be running it full out, you are going to need to install a larger feed to the garage and most likely hard wire it to the feed as the largest reasonable cost outlets and plugs are 50 AMP. To go beyond 50 amp you get into large pin connectors and it's simply not worth it. With the welder being 500 or more pounds, it's not portable anyway.

              Just a thought.

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              • #8
                Originally posted by madman View Post
                When I started shopping for a tig for aluminum. I was told a 250 amp tig would only ever be able to max out 225 amps using single phase current? Is this a true statement? I f so I would not bother with buying a 250 but instead perhaps a 225 or 200 amp tig. I primarily wish to weld crankcases on engines with it. Thanx Mike
                It's quite common for modern INVERTER based TIG welders to pull as little as 30 amps on a 220V single phase circuit while putting out 200 amps. Scale that up to 300 amp output and the input will be around 45 amps which is well within the capability of a single phase breaker.

                The documentation for each welder will specify the electrical needs. They will also specify the limitations. For instance my TIG will weld at 200 amps output on 30 amp 220volt circuit, but only 150 amps output on a 40 amp 120volt circuit.

                Dan
                At the end of the project, there is a profound difference between spare parts and left over parts.

                Location: SF East Bay.

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                • #9
                  Dynasty 280 is the answer. I think mine says 34 amps max on the tag. 100% duty cycle at 200 amps on AC. You will be welding those cases in the 200 amp range.

                  The syncrowave 200 I replaced would draw 54 amps at 200, but had like a 20% duty cycle.

                  You already know it sucks to not have enough oomph. Don't make that mistake again.

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                  • #10
                    Current isn't the only thing. For aluminum you need power, in watts, volts times amps. A welder can be buit for lots of amps with a lower circuit voltage which is common on inexpensive welders. Also circuit breakers have time current curves. A 50 amp breaker won't trip at 50 amps. At 60 amps it will trip after after maybe 10 minutes and say 3 minutes at 70 amps. This matches up pretty well with the duty cycle of inexpensive welders. So you can often get by with a fairly large welder on a small circuit. For tig welding aluminum a 250 amp machine is marginal at best. A 400 amp machine is so much better you won't believe it. You'll also have less trouble with the entire part getting really hot because your welding tume will be much shorter. Also for aluminum you want a water cooled torch. They are actually lighter abd easier to handle.

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                    • #11
                      Originally posted by garyhlucas View Post
                      Current isn't the only thing. For aluminum you need power, in watts, volts times amps. A welder can be buit for lots of amps with a lower circuit voltage which is common on inexpensive welders. Also circuit breakers have time current curves. A 50 amp breaker won't trip at 50 amps. At 60 amps it will trip after after maybe 10 minutes and say 3 minutes at 70 amps. This matches up pretty well with the duty cycle of inexpensive welders. So you can often get by with a fairly large welder on a small circuit. For tig welding aluminum a 250 amp machine is marginal at best. A 400 amp machine is so much better you won't believe it. You'll also have less trouble with the entire part getting really hot because your welding tume will be much shorter. Also for aluminum you want a water cooled torch. They are actually lighter abd easier to handle.
                      A 200 amp TIG Welder will do up to 1/4" aluminum nicely. Anything, more than that and you do need a more powerful welder. The buyer should really consider the limits of the work to be done before purchasing a welder.

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                      • #12
                        He mentioned engine blocks which are quite massive even on small engines. 1/4" strips and edge welds yes 200 amps is fine. Try welding a tab in the middle of a 24" square sheet of 1/4" aluminum and it is a completely different story.

                        Speaking of engine blocks. Many years ago a guy asked me to weld a broken off generator mount on the engine of a VW dune buggy. I made a beautiful weld all the way around using 4043 filler. While waiting for it to cool there was a pop and it fell clean off! I had him bring me a piece of another VW block and I sliced it into strips on the bandsaw, and used that for filler. That weld worked perfectly, no cracking at all.

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                        • #13
                          Originally posted by OhioDesperado View Post
                          First off the statement of a 250 Welder only outputting 225 on single phase may only apply to the specific unit they were selling.
                          The reason for it is that when you are connected with 3 phase you have one third more power connected to it due to the third phase.

                          ....
                          Not really the issue.

                          You can draw more current on single phase and get the same power. But it takes a good deal more current than the actual power requires, because the "power factor" of most ordinary non-inverter-type welders is quite bad.

                          The issue is in the "even-ness" of 3 phase power. When rectified and not filtered at all, 3 phase voltage never drops below approximately 86 % of the peak voltage. Single phase voltage drops to zero every half cycle, so a good deal of time is spent with input voltage well under 86% of voltage.

                          The power provided by 3 phase is constant, while single phase obviously is pulsating, varying from a high power to zero power twice per cycle. Welding is best with a constant power input, so a regular welder on 3 phase is likely to be smoother, even though the hot metal does tend to even out the overall effect, and the inductor in DC welders smooths the current.

                          Even though a standard type welder has a bad power factor on 3 phase also, the current per leg is less. And the peak currents can be lower because power flow is constant, not pulsating

                          An inverter welder can also provide a smoother weld on single phase, because it stores power to get through the times of zero power input. With a power factor corrector, included as part of many inverter type welders, the input current can be reduced to that which is required to provide the actual welding power.
                          Last edited by J Tiers; 02-19-2017, 10:32 PM.
                          2730

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                          • #14
                            Deleted.
                            Last edited by GNM109; 02-20-2017, 07:40 PM.

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