Parallel Inverter Welders - With Pictures!

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Here's a real Power Up story for y'all.  I didn't really expect this to work at that well... but it did fantastically well!Here's the story...A few years back, I bought a slightly used Canadian Tire 'Mastercraft' brand inverter welder off Kijiji for $200.  The attraction for me was that it was a portable 100 amp tig welder and 80 amp arc welder - and it came with the tig torch!  Actually this first welder came with $80 worth of extras - to the left off the welder in the picture.A couple months back, I bought an identical unit off Kijiji for $100 plus $30 shipping.  It was advertized as an inverter stick welder in an unopened box... but I knew it was a tig welder with torch!  Lucky for me that the tig torch was no too visible on the box!OK, so I had two identical inverter welders.  Here's a photo of the electrical characteristics.On a 120 volt, 20 amp input, the welder can output 80 amps stick at 21 volts or 100 amps tig at 14 volts with a 30% duty cycle.  In some previous posts, I had stick welded with the first unit .  While it laid down OK looking beads with 3/32 inch electrodes, when it came to fillet welds (sucking more heat away) it was marginal with 6011, 6013 and 7014 but definitely 'cold' with Lincoln 7018AC.  In fact I was told to 'get rid of that POS inverter!'Yeah, I was looking for a more powerful inverter stick welder and posted on that, "Cheap Inverter Stick Arc Welders - Thoughts?"  http://weldingweb.com/vbb/showthread.php?t=58082A couple of weeks ago, I decided to actually measure the output amps of the first welder using a DC clamp-on meter.- I measured a max of 65 amps with a 3/32 inch electrode (7014) and 80 amps on short circuit.- I measured a max of 80 amps with 1/8 inch electrode (7014) but that was low amps for that size rod.As I had suspected, that's just not enough amps for some 3/32 inch 7018 rods (e.g. Lincoln 7018AC) and most all 1/8 inch rods.The idea to try and parallel my two inverter welders came to me yesterday.  I thought I would be careful and check with a multimeter that there was no feedback from one to the other.  Even if there was no feedback, I felt that maybe the low 21 volt arc voltage might limit the amps to 80 or less anyway - same as one welder.So tonight, I tried it... and it worked - Frigging Super! 1 - Checked with a multimeter - there was no feedback from one to the other welder 2 - Hooked the welders up in parallel and WOWEEE !!!   POWER BABY!!! Here's the two welders, side-by-side.Here's me plugging in the two 120 volt, 20 amp plugs from the welders into the duplex 20 amp receptacle.Note: Both sockets are wired to one 12 gauge wire running to a single 20 amp breaker.  I popped the 20 amp breaker after running about 1 inch of 1/8 inch 7014 electrode with both welders in parallel.  For the final bead runs with 1/8 inch electrode, I changed to a 30 amp breaker - a bit high for #12 wire.Here's a photo of the two welder, each amperage knob set to 70 amps.  To the left you can see the electrode holder positive leads joined together.To be continued... give me time to post the rest please.Rick V 1 Airco Heliwelder 3A/DDR3 CTC 70/90 amp Stick/Tig Inverters in Parallel1 Lincoln MIG PAK 151 Oxy-Acet
Reply:The negative grounds were joined by simply clamping their ground clamps to the welding grill.Here's a photo of the positive electode holders joined to a new stinger cable.  For this quick test, each Tweeco-style electode holder was clamped to a small copper bar.  The end of the stinger lead was clamped to be copper plate using vice-grip-style pliers.Here's the results of messing around before the slag was knocked off the welds.  That steel plate was 3/16 inch thick, 6 inches long and 2 inches wide.Here's the results... YIPPEE... IT WORKED!!!When I tried that first weld with the inverters in parallel, I didn't know what to expect... but the huge change in the 3/32 7014 arc spoke loudly!  That 3rd bead on the top row was HOT!  Too hot - way wider and flatter than two individual welder beads preceeding it.  This could have been of the order of 2 x 65 amps = 130 amps.  Yeah, a whole lot of amps for a 3/32 inch electrode!I then tried (second row) the same 80 amps settings with a larger 1/8 inch diameter 7014 electode.  First two beads for each welder were almost cold but the 3rd bead (parallel welders) was hot!  This could have been of the order of 2 x 80 amps = 160 amps.  That's quite a bit of amps for a 1/8 inch electrode. In row three, I used an 1/8 inch 7014 electrode with the welders in parallel.  I ran a series of short beads with the welders both set at 40, 50, 60 and 70 amps.  The results look more like I'm getting what:- 1.5 x that: 60, 75, 90 and 105 amps? (last bead looks hotter than 105 amps)- 1.75 x that: 70, 88, 105 and 123 amps?- 2 x that: 80, 100, 120 and 140 amps?Anyway, that's the story... it sure was fun!Rick V 1 Airco Heliwelder 3A/DDR3 CTC 70/90 amp Stick/Tig Inverters in Parallel1 Lincoln MIG PAK 151 Oxy-Acet
Reply:IF both welders are plugged into the same circuit, I don't think you'll be exceeding 100 amps or so.My name's not Jim....
Reply:Originally Posted by BoostinjdmIF both welders are plugged into the same circuit, I don't think you'll be exceeding 100 amps or so.
Reply:Try two separate plug circuits instead of the same plug (if you have access to 2 different circuits in the shop area)Having a Harbor Freight 80A inverter & a 100A Forney unit I found they weld better using 1/16" rods....maybe 3/32" for heavier max output... anything larger just seemed not to flow well. Since you're doubling up though larger rods should be usable. I've often wondered if this could be accomplished since I read of it being done with a couple of Millers somewhere.(guess it can) I've never had 2 identical units to test the idea (or the guts to chance it if I did) I'm assuming you're end goal is more juice for Tig welding? That would be interesting too.Thanks for the pictures of your test... I really like both my "little" inverters and usually use them for little stuff around the shop that needs a quick fix...they're just too easy to grab and weld with. I found a 1930's AC small box welder that puts out 80-100A and bought it because it was cheap & in excellent condition (almost new). It welds as well as the inverters (just AC) but weighs about 45# so it sets on the bench.These little inverters are highly underated as far as their abilities are concerned... Enjoy yours and have fun experimenting with the dual output...
Reply:you do some really odd things. Just so you know, you can buy/make a y cable that ties both positives together and has a female connector for you to plug your stinger in. We do it all the time for air-arcing with xmt 304's.ESAB MigMaster 275Miller Econotwin HFMiller Syncrowave 250
Reply:Originally Posted by mudbugone... I've often wondered if this could be accomplished since I read of it being done with a couple of Millers somewhere.(guess it can) I've never had 2 identical units to test the idea (or the guts to chance it if I did)...
Reply:if you are on 1 30 amp circuit you probably don't have enough input power which is limiting your output power. When i had my 110v mig, I could VERY clearly tell a difference in peak power on a 15amp vs 20amp circuit.ESAB MigMaster 275Miller Econotwin HFMiller Syncrowave 250
Reply:Ah-Ha!  I found the problem... in Test 2 the jaws of the clamp-on ammeter had opened about 1/8 inch with the two ground cables passing through - that's why the low amperage readings when running in parallel. A further test will be needed to confirm that but based upon the simple amp addition results of Test 1, it appears the individual welder delivered amperages just add together. That would mean welds H and I were made with about 72 + 74 = ~146 amps... and the welds look it.Rick V 1 Airco Heliwelder 3A/DDR3 CTC 70/90 amp Stick/Tig Inverters in Parallel1 Lincoln MIG PAK 151 Oxy-Acet
Reply:You should break the connection tab between the top and bottom outlet and run some 12/3 cable to it for a hot,hot, shared neutral, and shared ground to a dual 20a breaker. This way a single breaker cuts all power into the outlet box, but you do get 40 amps total. Shared neutral is allowed as it will never carry more than one leg of power. IE, when both units are running full out, neutral will have no current through it.Running a 30 amp on 12 guage wire is like you said, a bit much.miller syncrowave 250hobart handler 140home made 400 amp engine driven in progress...
Reply:Originally Posted by claymans13if you are on 1 30 amp circuit you probably don't have enough input power which is limiting your output power...
Reply:I'm not an expert on inverter welders but I would think putting them on different phases with double pole breaker may be a problem. I would keep them on the same phase by skipping a slot in the breaker panel and then using 2 20amp breakers and 12 gauge wire to feed circuit.
Reply:transformerr machines in AC mode might end up with issues, but an inverter by design will have no issue.miller syncrowave 250hobart handler 140home made 400 amp engine driven in progress...
Reply:Some more testing results...Test #3 used a large 3/16 inch thick plate and 1/8 electrodes 7014+ and 6013+.The ground clamps cleaned with a wire brush and clamped to the welding grill via a copper block.  Both ground leads passed through the ammeter C-clamp and were left there with no gap visible on the C-clamp jaws.  Welders were turned on or off as required.1/8 inch 7014+Welder 1: 72 - 90 amps, average 76 ampsWelder 2: 78 - 95 amps, average 86 ampsParallel welders (each set at 80 amps): 125 - 158 amps, average 135 amps falling slowly to 115 amps while welding.  The decreasing amperage was real - observed two times.  Maybe that's the #12 wire heating up with 30 amps?Let's see:Separate welders = 76 + 86 = 162 amps; that's greater than the parallel output of say 125 amps.The average output of the separate welders = (76 + 86)/2 = 81 ampsThe increase in parallel welder current is about = 125/81 = 1.54X1/8 inch 6013+Welder #1: 88 - 102 amps, average 88 - 95 amps or say 90 ampsWelder #2: 88 - 102 amps, average 95 ampsParallel welders: 132 - 148 amps, average 135 - 145 amps, say 140 ampsLet's see:Separate welders = 90 + 95 = 185 amps; that's greater than the parallel output of say 140 amps.The average output of the separate welders = (90 + 95)/2 = 92.5 ampsThe increase in parallel welder current is about = 140/92.5 = 1.51XI'm not sure why the parallel current is not just the simple sum of the output of each individual welder.  Maybe the current draw is heating up the #12 current supply wires and dropping the input voltage?Input current draw = (output watts / efficiency factor) / input voltageInput current draw = (140 amps x 21 volts / 0.85) / 117 volts = 29.5 ampsI'm not certain what happens when you push 30 amps through #12 wire.  As already suggested, I should try separate 15 amp circuits and see if I observe that falling welding current after welding for a few seconds.OK, paralleling inverter welders to get more welding current works for me!  For the future, I could use some refinements to my input power wiring and to my welding output leads.Thanks for listening and for the great suggestions...Rick V 1 Airco Heliwelder 3A/DDR3 CTC 70/90 amp Stick/Tig Inverters in Parallel1 Lincoln MIG PAK 151 Oxy-Acet
Reply:Interesting post- I, too, thought that the power might be voltage-limited but apparently not!Those bayonet connectors are called 25mm Dinse connectors. Lenco ( www.profaxlenco.com ) makes male and female connectors which you can use to rig up your adapters. Should be available at your LWS.JohnA few weldersA lot of hammersA whole lot of C-clamps
Reply:Originally Posted by Silicon-basedInteresting post- I, too, thought that the power might be voltage-limited but apparently not!
Reply:Bravo! Proof this works is very cool.
Reply:Originally Posted by farmallBravo!  Proof this works is very cool.
Reply:Great research and results as well as your additional information on this in great detail. I've often wondered how this would actually work.As you stated earlier you could use this for additional power capacity without a 220v outlet. I'm sure there are those that don't have a 220v line that might actually use your information. You fell into a chance to try this since you purchased 2 identicle welders for cheap. I might give this a go if I find another 80A inverter from HF for some extra power.Thanks for taking the journey into the unknown and more importantly for taking the time to share the outcome with all of us.What do you imagine the results might be should you use this for Tig welding ?Last edited by mudbugone; 12-21-2011 at 10:15 PM.
Reply:Originally Posted by mudbugone... What do you imagine the results might be should you use this for Tig welding ?
Reply:Ooops, one more interesting & rather weird effect I forgot to mention.When the welders are paralleled the arc 'sings'! Yeah weird or what!  I kept wondering if something was wrong.I noticed that the singing became noteably louder the longer the arc.The explanation came to me this morning...Each of these inverter welders operates at high frequency above the audible range; something like 18,000 Hz+, way above the transformer-based welder's 60 Hz.  Operating a singel inverter welder, you can't hear this... it might drive your dog nuts though. When you operate two such welders in parallel, they are both driving a common arc, each pulsing at it's own internal frequency, say f1 and f2, which are close but not exactly the same.  This creates a beating sound - like you hear when two of more engines are running together but at slightly different speeds.  You get a throbbing sound superimposed on the normal engine noise.  e.g. Twin or four engine propellor driven aircraftI hear this type of throbbing sound when I operate my my small air compressors together; if I run all 4 of them it sounds like a bloodly four-engine bomber!  Thrum-thrum-thrum-thrum.... What's happening is called hetrodyning... you get the sum and difference of the frequencies.e.g. f1 + f2 and f1 - f2.  Suppose my welder frequencies are f1 = 18,000 Hz and f2 = 18, 800.  The sum of the frequencis is 36,800 Hz - way above the audible range so you can hear that.  However, the difference of the frequencies is 800 Hz and you can definetly hear that!What started out as annoying is actually helpful.  The shorter the arc, the quieter is the 'singing'.  So now I have two feedback mechanisms - the visible length of the arc and the loudness of the singing!   Keep the sound down (short arc) and I get a good weld. Maybe 'Darth Welder' should become the the 'Singing Arc'. Rick V 1 Airco Heliwelder 3A/DDR3 CTC 70/90 amp Stick/Tig Inverters in Parallel1 Lincoln MIG PAK 151 Oxy-Acet
Reply:interesting!  BTW, i bet teh reason you do not get 2x the current ( ie 80 + 80 = 160 ) is the voltage is not changed at all, so that is just the max current that will flow at that voltage with whatever load is created by your two cables, clamp / rod holder and rod / arc.  I bet you could get more current out if you upgraded wires to higher gauge, used good clamp / holders, and had good solid connections.. but do you need more ? is it worthwhile?  Maybe a bigger Rod would flow more as the steel in the rod is the biggest resistor in your circuit.miller syncrowave 250hobart handler 140home made 400 amp engine driven in progress...
Reply:Originally Posted by jdchmielinteresting!  BTW, i bet teh reason you do not get 2x the current ( ie 80 + 80 = 160 ) is the voltage is not changed at all, so that is just the max current that will flow at that voltage with whatever load is created by your two cables, clamp / rod holder and rod / arc.  I bet you could get more current out if you upgraded wires to higher gauge, used good clamp / holders, and had good solid connections.. but do you need more ? is it worthwhile?  Maybe a bigger Rod would flow more as the steel in the rod is the biggest resistor in your circuit.
Reply:UPDATE...I rewired the welder inputs using 16 foot #12 gauge extension cords.  I plug each extension cord into a separate 20 amp breakered wall outlet.  I plug each welder into it's extension cord using a short 6 inch long 15 amp plug to 20 amp socket.I changed out the welder cables.  Originally each welder used a  total of 16.5 ft (9.5 electrode and 7 ft ground) of #7 gauge cable.  Each #7 cable was carrying a maximum of 70 to 80 amps.  I wanted to increase the ampacity.From each welder's + connector, I used 1 ft of #4 red cable joining to a 'T' to 10 ft of #1 gauge cable going to the electrode holder.From each welder's - connector, I used 1 ft of #4 black cable joining to a 'T' to 10 ft of #1 gauge cable going to the ground clamp.The first picture shows the brass 'T' air fitting I used to join the cables from the two welders: drilled, tapped for 3/8 inch NC, stainless steel set screws used to secure red/orange #4 cables and #1 black cable.  I used thin brass sleeves inside the fitting so as not to cut the copper stands on the fitting threads.The second picture shows the completed fittings wrapped with insulating electrical tape.  Also shown is the electrode holder and ground clamp I chose to use.  The ground clamp is interesting as it uses bronze conductors (joined with copper braid) inside a steel camp.  Sort of the best of both worlds: bronze for electrical conduction but encased in steel to prevent breaking the bronze should the clamp get dropped, etc.The third picture shows the average welding amps (140 - 145) and maximum amps (~170) welding amps recorded by the video camera while welding.  Both welders were set at max amps - 80 amps on each dial.Shown is the result using 1/8 inch 6013 electrode + at an average of 145 amps.  Normal amperage variation was 140 - 150 amps.  1/8 inch electrode ran smooth and nice = very good.Also shown is the result using 5/32 inch 7014 electrode + at an average of 145 amps.  Normal amperage variation was similar, 140 - 150 amps.  This larger 5/32 inch electrode was too much metal for the paralleled welders.  I struck the rod several times on starting.  It was difficult to maintain the arc - I could not maintain a normal arc length without the arc going out.  I had to use a very short arc.  Still the weld bead, particularly the first few inches (left side) went down well enough.  However, I felt I didn't have enough arc volts to run this 5/32 electrode.On the other hand, I don't think my Lincoln AC/DC 225/125 could run this large size electrode on DC either... 125 amps would not be enough.Overall, I'm quite pleased this paralleling welders worked so well.Alone, each 80 amp inverter welder was good for 65 amps max with 3/32 inch electrodes - just enough amps for 6011, 6013 and 7014 but really not enough for 7018.  With 1/8 inch 7014, I could get the max 80 amps out of each welder but that 80 amps was too low to run most any 1/8 inch electrode (OK, maybe 6010/6011).Paralleled together, the welders could run all 3/32 and 1/8 inch electrodes that I had.  I could even get a marginal result with 5/32 7018.That was/is a major improvement in cabability... I question keeping my two remaining big box transformer welders?  If I stay with 1/8 inch or less diameter electrodes, the paralleled inverters are more convenient to set up and use... anywhere.Yeah, this worked out GREAT! Rick V 1 Airco Heliwelder 3A/DDR3 CTC 70/90 amp Stick/Tig Inverters in Parallel1 Lincoln MIG PAK 151 Oxy-Acet
Reply:I would get rid of the big trannies and look at getting rid of the little inverters also. I would see about getting the TA 161stl since they are on sale at cyberweld right now. As always your very thorough with your post but the one thing I see you don't address are the volts of the output the machines run at. Yes they are cc machines but the TA unit runs at 26.4v vs the 21v of your units. The extra volts will let you run 5/32" 7018 rod. I don't the TA 161stl but I do have the TA 185 which has the same stick welding output and don't have any problems running 5/32" 7018.I would get rid of the big trannies and look at getting rid of the little inverters also.
Reply:So, I take it the CSA certification is now void? Good job - interesting topicFire!, Fire! Oh wait, that's my torch...Lincoln PT-225 TIGLincoln 175 MIG
Reply:Paralleling welders is an old shipyard trick.  If you have multiple welders sharing a common ground you can mess with your buddy while he is welding by taking your welding electrode and sticking it on the screw in the connector for his welding lead.  You will double his amperage by paralleling the two welders and make his welding rod explode.  Nobody will be any where near his welder to mess with his settings so he will be very confused.
Reply:I wish I'd known that trick in welding school....
Reply:Hi RickV,You have inspired me to try a similar experiment... Craigslist just provided me with a Century 295A AC welder similar to one I already have. Both machines have 2 taps, a 'high' setting (actually lower voltage) and a 'low' (higher voltage) tap. The 'low' tap is better for most welding but is only 230A max and 120A at 100% duty cycle.I'm going to try paralleling the higher-voltage taps of both welders which should give me (hopefully) close to 460A max and 240A at 100%, with adequate voltage to make use of the added currentI have 2 separate 240V circuits, one 50A and one 60A, which should be enough given the duty cycles of the welders. Just have to make sure the phasing is correct. I'm almost done cleaning and fixing up the new machine, and I'll try it out as soon as I recover from the holidays.  JohnA few weldersA lot of hammersA whole lot of C-clamps
Reply:Hey John... that will be Starting The New Year With A BANG!If we don't hear from you by Jan 5th, we'll have to assume you got the phases wrong!  Yeah, try it (with care ); the results of paralleling two 230 amp AC welders should be interesting... you know in case you ever need to run a 0.5 inch electrode. Rick V 1 Airco Heliwelder 3A/DDR3 CTC 70/90 amp Stick/Tig Inverters in Parallel1 Lincoln MIG PAK 151 Oxy-Acet
Reply:Nope, not dead yet! Just busy with "real" work.Experiment was a rousing success; despite the 2 welders not being exactly identical (as you can see) they paralleled with no problem, the arcs were powerful but smooth.The ground clamp from each welder was clamped to the table. The wacky-looking cable connects the outputs of both welders to an LC40 connector for my heavy-duty stick cable. The bottom bead in the pic is 7/32" 7016 @ 240AThe one above it is 3/16" 7024 @ 300AThe top bead is 1/4" 11018M @ 400ADon't try this at home, kids!  Attached ImagesA few weldersA lot of hammersA whole lot of C-clamps
Reply:Glad you made it out alive Silicon-based! Good to hear paralleling worked for you as well... both machines were AC only right?The bottom bead in the pic is 7/32" 7016 @ 240A - Looks 'cold' to me.The one above it is 3/16" 7024 @ 300A - Looks a mite on the 'hot' sideThe top bead is 1/4" 11018M @ 400A - That look way too 'hot'Hmmm... big electrodes 3/16, 7/32 and 1/4 inch at high 240, 300 and 400 amps.Yes, your trials and photo's rounds out this thread nicely!  Good Job! Rick V 1 Airco Heliwelder 3A/DDR3 CTC 70/90 amp Stick/Tig Inverters in Parallel1 Lincoln MIG PAK 151 Oxy-Acet
Reply:This thread just keeps getting better.  Anyone have two buzzboxes that'll do DC?
Reply:Originally Posted by farmallThis thread just keeps getting better.  Anyone have two buzzboxes that'll do DC?
Reply:Nah, those beads ain't gonna win any beauty contests  , more of a "proof of concept"There is a practical aspect to this, though. Sometimes AC is actually the preferred process, especially at high currents- try running a fillet with 1/4" rod on DC sometime AC welders that can put out over 400 Amps aren't that common and they sure as he11 aren't light and portable! The 2 welders together weigh about 220 lbs. and cost me $140 on C/L- a bit Frankenstein but hard to beat! JohnA few weldersA lot of hammersA whole lot of C-clamps
Reply:Originally Posted by farmall... I'd sell the Lincoln AC/DC 225/125 since they have high name recognition, and keep the Linde...
Reply:Really interesting thread, guys! Rick_V, my hat is off to you. Awesome idea, great testing, and great data  Very cool read. Good thinking, and I'm glad you expanded what you can do with the small machines! I have done some experimenting with my 140A, 110V MIG. I don't have 2 MIG's to parallel, sadly  But I have taken video of both voltage & clamp-on AC current readings while welding. My measurements have been on the AC-input side, since my clamp-on meter is AC-only. I've used this to check the voltage getting to the plug using different extension cord setups. I have also checked my gun output voltage at different settings (not actually while welding, though). I am working on getting a higher-capacity plug wired to the garage. Currently, I have 14 gauge wire on a 15 amp circuit. Interestingly, my welder seems to pull about 20A at "C" voltage, and 25A at full "D" voltage. I have not tripped a breaker yet. But I also have not tried to weld at 25A for more than maybe 10 seconds or so at a time. I have wondered about something that you sort of touched on. I'm curious to run extension cords to two different 15A outlets (selected so they are both on the same leg, 0V between the cords, not 240V). Then tie those cords together, and feed the welder that way. That's a quick & dirty way to "fake" having a higher-amperage circuit. It would be more like having a 30A circuit. Should help avoid tripping a breaker, and would also provide higher voltage to the welder (now splitting the 25A across 2 sets of power leads, so there would be less voltage drop through each set of wires). Several people have mentioned that a 20A circuit provides more power with their 110V MIG, vs a 15A circuit, so this approach might help get a bit more "oomph" out of mine. To be clear, I know this is potentially hazardous. The outlets must be selected so they are on the same leg, providing 110V (0V between them). This might need to use a male-to-male cord, to tie the two extension cords together, which is dangerous. Though going through power strips, with on/off switches, might let you connect all the exposed male plugs, *then* switch on the power for each strip. This would not be meant as a long-term solution, more as a test. I'm trying to get a proper, higher-current outlet. But, in a pinch, if you needed more power at a location with only 15A, this could help provide more current. Lincoln put a 14 gauge power cord on the welder. It seems like going to 12, or even 10 gauge, could also help a bit. I know, a 220V MIG would provide much more capability, but this is what I have, and I don't even have a 220V outlet currently  And this seemed in keeping with the spirit of the thread, doing more with what you have.
Reply:Hey RedOctobyr,Yeah, IMO making up a T-type cheater cord for a test is a great idea.I have one that I keep around.  Designed for what you want, two 115 volt 15 amp same phase plug inputs for one 115 volt 15/20 amp receptacle outlet.... that I can pull 30 amps through.  The safety key is to always verify that you have zero volts - same phase.Rick V 1 Airco Heliwelder 3A/DDR3 CTC 70/90 amp Stick/Tig Inverters in Parallel1 Lincoln MIG PAK 151 Oxy-Acet
Reply:I forgot to mention - if you can get 30m/100ft 12 gauge cords at Costco for $35, that seems like a pretty great deal. I thought I was doing well to get a 50ft 12 gauge cord at Harbor Freight recently for $30. If I went to Home Depot, it would be $50+ for 50 ft. And I have no idea if this is just dumb, I do not really know anything about arc welding. But the output voltage of your machines was mentioned, where even in parallel, they are still putting out 21V. If you needed more voltage for something, could you connect their outputs in series, to double the voltage, instead of the current? Ground, to electrode holder, to ground, to electrode holder? I have no idea if double the original voltage would cause some other sort of problem (either just electrically, or with the arc). You just got me thinking about it, since voltages were mentioned, along with all this flexibility you've discovered.
Reply:Yep on the Costco cords - same here in Canada... just a few $ more, but still the best deal.When the 3rd welder arrives (stalled in Easter post) the intent is to simultaneously monitor both the arc voltage and current so we nail that down.NO... wiring welders in series is not a good idea!  For many reasons..... Blue Smoke!Rick V 1 Airco Heliwelder 3A/DDR3 CTC 70/90 amp Stick/Tig Inverters in Parallel1 Lincoln MIG PAK 151 Oxy-Acet
Reply:Hi Rick,As you may know, the voltage requirement for an arc increases with increasing current. Therefore, paralleling 3 welders will probably not give you 3 times the current, but you will probably be close to 100% duty cycle at whatever current you do get. Provided that you have 3 good 120V circuits! I have connected 2 welders in series, but it is definitely a don't-try-this-at-home-kids scenario. Not so much because of damage to the welders, but because the blue smoke may come out of your chest cavity!   JohnA few weldersA lot of hammersA whole lot of C-clamps
Reply:Originally Posted by Rick V... I'm trying to find a 3rd at a good-deal price.  If 1 was good for 70 amps, 2 for 140 amps, I'd like to see if 3 would go to 210 amps!
Reply:REMINDER: WHY AM I DOING THIS?The concept is to parallel low cost, low output welders to achieve a substantial increase in welding current.  This post has shown that one can use two 70 amp DC inverter welders in parallel to obtain about 140 amps of welding current.Three Welders in ParallelOK, I acquired my third identical CTC inverter welder.  Here they are all sitting side-by-side on a shelve.Each welder is rated for 80 amps max output in stick mode.  Past welding experience with the welder has shown that 70 amps max output is more the norm.Welders 1 & 2 were already harnessed together.  Welder 3 was wired in parallel by:a) clamping the electrode holder to a copper bar clamped to the (+) cable joiner for welders 1 & 2. b) running a separate (-) ground lead to the welding table.NOTE: Arc VoltageTo measure the arc voltage, one has to measure the voltage between the ground clamp (see above photo) and the electrode holder (see photo below).Wires from these arc voltage pick up points run to the digital voltmeter.Welding amperage was measured using a clamp-on ammeter measuring the single (+) welding lead headed to the electrode holder.  In practice I use a small digital camera in movie mode to record the video and audio while I weld.  This records the simultaneous values of arc voltage and welding current at any moment in time before, during and after welding.Continued on next post....Last edited by Rick V; 04-11-2012 at 03:24 PM.Reason: spell errorRick V 1 Airco Heliwelder 3A/DDR3 CTC 70/90 amp Stick/Tig Inverters in Parallel1 Lincoln MIG PAK 151 Oxy-Acet
Reply:SO... BIG QUESTIONDo three 70 amp welders in parallel deliver 210 amps?YES!!!Here's the recorded video picture using a 1/8 inch 6013 electrode... 206 amps!Changing to a larger diameter 5/32 inch 7018 electrode permits more current to flow... 224 amps... but we are at the max of the paralleled welders.Here's the details... if you don't want details you can simply skip to ***********Individual Welder Test 13/32 inch 6013 Welder at full output (80 amps)Welder #.....Volts.....Amps......1.............25 open....0.........1.............21-24........64-80, ave = 75......2.............25 open....0.........2.............21-24........64-78, ave = 72......3.............25 open....0.........3.............21-25........62-77, ave = 74Observation:  Each welder outputs very similar voltage and current when driving the same 3/32 inch 6013 electrode.Double Welder Test 13/32 inch 6013 Welder at full output (80 amps each)Welder #.....Volts.....................Amps.....1+2 .........26 open...............0........1+2..........27-33 (ave 31)....95-115, ave = 105.....2+3 .........26 open...............0........2+3..........25-33 (ave 30)....95-125, ave = 110.....1+3 .........26 open...............0........1+3..........25-31 (ave 27)....104-140, ave = 122Observations:1. The arc voltage is higher with two welders, rising from about 23/23 volts to 28/29 volts.2. Compared to a single welder max output of 75 amps through the 3/32 6013 electrode, doubled welders give a maximum output of 112 amps.  This is only 1.5 times the output of a single welder.Double Welder Test 2 - larger diameter electrode1/8 inch 6013 Welder at full output (80 amps each)Welder #.....Volts.....................Amps.....1+2 .........26 open...............0........1+2..........18-24 (ave 19)....112-158, ave = 150.....2+3 .........26 open...............0........2+3..........18-24 (ave 22)....130-166, ave = 145.....1+3 .........25 open...............0........1+3..........17-23 (ave 19)....140-180, ave = 160Observations:The change from a 3/32 to a 1/8 inch 6013 electrode created significant changes; the arc voltage dropped and the welding current rose.  (I guess the 3/32 inch electrode was heating up at the 110 amp currents and giving a higher resistance.)Where are we and what do we know so far?One nominal 80 amp welder pushes 72-75 amps through a 3/32 6013 electrode.Two nominal 80 amp welders in parallel push 105-122 amps through a 3/32 6013 electrode.Two nominal 80 amp welders in parallel push 145-160 amps through a 1/8 6013 electrode.Double Welder Test 3 - even larger diameter electrode5/32 inch 7018 Welder at full output (80 amps)Welder #.....Volts......................Amps.....1+2 .........26 open...............0........1+2..........18-23 (ave 21)....130-170, ave = 155.....2+3 .........26 open...............0........2+3..........19-24 (ave 22)....130-165, ave = 150.....1+3 .........26 open...............0........1+3..........19-24 (ave 22)....135-165, ave = 155Triple Welder Test 11/8 inch 6013 Welder at full output (80 amps)Welder #.....Volts......................Amps..1+2+3........25 open................0.....1+2+3........22-24 (ave 23).....178-206, ave = 195Triple Welder Test 25/32 inch 7018 Welder at full output (80 amps)..1+2+3........25/26 open...........0.....1+2+3........20-25 (ave 23).....160-224, ave = 205********************************The final picture shows the weld beads made during the tests.  I lost track of the middle beads.You can see the 1 welder 70 amp (3/32" 6013) results on the right side of the plate.You can also see the Super HOT looking 3 welder 200 amp (5/32" 7018) results on the left side of the plate.Yes, it looks way, way too hot... isn't that great? So there it is...Paralleling three DC inverter welders can output three times the maximum current of any one welder! Last edited by Rick V; 04-11-2012 at 03:22 PM.Reason: spell errorRick V 1 Airco Heliwelder 3A/DDR3 CTC 70/90 amp Stick/Tig Inverters in Parallel1 Lincoln MIG PAK 151 Oxy-Acet
Reply:What makes this great is that instead of merely asserting it will work in theory, you prove it works in practice!That should also translate to increased DUTY CYCLE at lower amp settings.Instead of a single failure taking out the whole "combination", you'd merely have reduced max output.I can see it now! Instead of Miller "eight packs" at the job site, row on row of little inverters hooked together like PCs in a Google server farm. Also: "DO 4!"
Reply:now test 3 of them in series.. plasma cutter power source.miller syncrowave 250hobart handler 140home made 400 amp engine driven in progress...
Reply:Ok, that's over my pay grade. I just have REAL WELDERS that you turn on and weld ! Next, why not try to run off generator ?  Great job, impressive !
Reply:That's awesome. Great work! And I'm glad you're really seeing a benefit with them. Personally, I think this is cool. For those of us without high-current 220V outlets, it's more feasible for me to run a few 110V devices in parallel at the moment. I wish my clamp-on meter did DC, but it's AC-only, so I can't check my MIG current, just voltage. And I haven't yet gotten brave enough to try and check my voltage while actually welding. I've just checked it from the gun to ground, open circuit, with no arc. I do like your voltage idea, though. Maybe I could try and wrap a wire around the MIG contact tip, then use that to keep the meter leads a bit further away, while reading voltage. I don't want to mess up the leads.
Reply:Great test, Rick- glad to see that the voltage held up.Now, who has 2 or 3 of those big honkin' 650A 3-phase welders that they can connect together? A few weldersA lot of hammersA whole lot of C-clamps