QFTB #7: What are volt/amp curves of welders?
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- Опубликовано: 8 июл 2024
- In this episode we tackle figuring out what volt/amp curves are of welders and why it matters.
0:00:00 Intro and overview
0:06:32 Volt/amp curve charts
0:13:15 Info on transformers and conclusion
Excellent explanation and visual examples!
The laws of the Universe must be obeyed!
It’s good to have a clear simple model to understand complicated subjects. There is no real need to go into sophisticated science and mathematics to understand there are limits to what we can expect out of our machines.
That being said, I am always amazed at videos of very talented and creative people, using very primitive machines, sometimes cobbled together from scraps, can do with what to us is junk. Under their particular circumstances - “Necessity” drives creative ways to get things done, and they provide for themselves and their families, and they have my respect. We are lucky to have easy access to a wide variety of equipment. It is humbling to say the least, and I can’t complain if my welder has its limits. I simply must work with what I’ve got, and this video helps me to better understand that.
I will ADD; I will dime myself out and say I thought I couldn't learn much out of this video... And now I REALLY want to know, learn and LISTEN to anyone who has already 'thumbs-down' this video! There is so much incredible explanation and understanding presented that I NOW understand why some machines can't 'run' 6010' or the 'limitations' of 120V welders - until today. I'm literally in awe when I sit down with Greg's videos; I get schooled quite often and I for one, am better for it!
The laws of the universe are unfortunate road blocks aren’t they lol. You are correct, it’s crazy to see what primitive machines that someone with a bunch of skill can use to make stuff. Having limitations isn’t a hinderance to creativity fortunately 😀
Very Nice Job Explaining Greg!!
I learned something new. Thank you!
best wishes Greg, love everything you do, cheers from an old fart in Orlando, Paul
Very well explained!
Addition:
The manufacturers "trick" physics by overloading the input circuit periodically for a short time to get higher output. That works because breakers usually have two working principles 1. An electromagnetic (that trips the breaker at a amperage that is N-times higher than the nominal load - but then it Acts emidiately) and 2. a thermal actuator (that needs time to reach the critical energy - it works on lower overload values but is kinda lazy.
Cheaper Inverters are actually drawing more power form the input than they are rated and get away with it (often) because this done only a limited time. But on longer weldseams they are notorious for tripping breakers.
Yep 100%. Case in point the arc captain 130 I have been trying to test for a couple weeks that kills my generator despite claiming only 20a current draw. It’s so bad I don’t know how it’s legal to sell lol. 35a input loading on 120v just to weld 1/8th in steel 😅
Liv'n n learn'n. Thanks Greg.
Great education! I remember learning this stuff, in my early 20s, doing a welding inspection course. Somehow, I forgot most of it, until watching this video, so, thanks!
No problem 😀. It’s hard to remember it since for the most part it’s not something that helps you out every day lol.
Good explanation Greg. I’d like to add that you can’t maintain 2400 watts on a 20 amp 120v circuit. At most, a breaker won’t operate for more than 15 seconds or so at a 90% load. It could drop to 80% load for a longer period. So realistically, no one is going to get more than about 2150 watts longer term. It’s amusing when I see small, cheap 120v welders advertising over 120 amps and even 200 amps at 240. The ones I’ve tested barely do 100 amps at 120v for more than a few seconds and the 200 amp spec at 240 usually turns out to be 150 or less.
For very short duration obviously a breaker will hold a higher load, and no doubt welders abuse this often. Just like you said, a cheap welder advertising 120a when you know it has poor power factor and efficiency. 75% of the time they are lying about output, and the other 25% they are overloading the breaker and causing it to trip lol. Speaking of that, I bought an arc captain 135 and they claim over 120a of stick power on a 20a breaker with a .65 power factor while only having an inrush a bit over 20a 😅😅. It tripped my 30a generator breaker welding 1/8th steel at 2/3rds max output. I hate lies lol.
As an electrician, I’m pretty sure the breakers can hold on for longer than that, if you’re actually close to their rating.
When wiring a building you can feed a load that’s up to 100% of the rating of your wire and breaker, as long as it doesn’t run continuously for more than 3 hours at a time. For “continuous loads” (ones that run full power for over 3 hr) you don’t want to load a wire or breaker beyond 80% of its rating. But that’s more of a safety/reliability margin, and breakers will typically hold their rated current continuously.
Schneider Electric claims that for a 15 second overload time, their single pole 20A breaker will take somewhere between 30 and 50A to trip.
At the end of the day it’s just more room for the cheap welding machine manufacturers to lie about their specifications and build things that aren’t as safe or useful as you’d think from reading their sales pitch.
I think this video has convinced me that if I get into welding, I’ll buy a transformer based 240V/50A input machine with a DC option. I would be able to use 6010 that way. And out of curiosity I could look at the transformer and see how it actually worked to maintain the selected current across a range of output voltages.
Plus I’ve heard some of the cheap inverter machines don’t accurately produce the amperage you set them for, which I’m sure is easy enough to compensate for but it seems like a bad thing while trying to learn.
Obviously cost is a big drawback of the transformers, especially since I’d also be buying electrodes, a decent hood, gloves, and welding jacket, practice steel, etc. But I have seen old welding transformers for sale, second hand, for similar prices to a new cheap-brand 120V inverter machine.
So the older transformer machines (like my dial arc 250) are still exceptionally good welding machines. They are easy to strike arcs on (because they can hold high voltage easily). They generally don’t have any issues whatsoever running 6010 (the industrial welders that is, some of the cheaper transformer machines like the sears branded ones might not run 6010). They are simple, fairly quiet, and will last forever. The main drawback is they are very power hungry, and really need a 50a power outlet.
You can often pickup a dial arc 250 like I have for less than 300$. That’s roughly the same price as many cheap inverter stick machines. That’s really not a bad deal for an indestructible shop welder.
i always get so excited when i see an upload from you, thank you greg
No problem 😀
Must interesting explains a lot !!!!❤❤
great video greg, i just sold my miller thunderbolt 225 that was made in the 70s and i regret it big time that thing ran everything even on a 30 amp line
Those are indestructible and had a similar volt/amp curve as the dial arc, so they ran rods really well. To me the main downside is the size and weight, but sitting in a shop where that doesn’t matter they really worked well. I like the modern settings of most inverters but I won’t be selling my dial arc anytime soon lol.
I am learning that I should be aware of the minimum voltage required to run any given stick rod, or tig arc, or spray transfer. This way I can look at a machine's volt/amp curve to see if that machine can deliver what I want/need. am I understanding this correctly?
With tig it operates at such a low voltage that any stick power source can tig weld without a problem. With stick, if you want to run particular rods (6010) and the volt-amp curve of a machine can’t produce say 40v at 90a, the welder won’t run 6010. The same can be said for carbon arc gouging (air arc) which needs 50v at 200a to run common rods, which is way higher than most welders can supply. The big dial arc 250 I have isn’t bothered by 6010 but my cheap Amazon special won’t run it because it won’t produce enough voltage. To further complicate things it’s very common for companies to mention something like “high open circuit voltage (or OCV)” and “80 volts OCV” in marketing their stick welders. That’s a good thing to start rods (higher resting voltage makes it easier to start a arc just like it’s easier to get shocked by 120v over a 9v battery) but it has nothing to do with actually running rods.
Most 1/8th rods run at 19 to 24volts. 6011 is around 26-27 and 6010 is 30-33v. Many welders will run 6011 that won’t run 6010 because they produce just enough voltage for them. On face value being able to run 6010/6011 properly (or at all) might not seem like a big deal, but stick welders that will run 6011/10 well often flat out weld better with other rods too. They often start easier, are more forgiving, and when welding a gap the arc stays lit rather than cutting out. A gap requires more voltage to weld due to longer arc length, and it becomes hard to keep even 7018 lit on welders with a poor volt-amp curve
Always coming with knowledge, thanks Greg.
Would you be interested in doing a video on the internals of the arccaptain?
I have filmed most of the video on the arc captain, including the internals. I ran into a major issue testing it, the machine almost kills my generator on a 30a 120 plug. I had to resort to going to a household breaker to even doing testing. I am finishing up testing this weekend and hopefully have the video out shortly 👍.
This topic reminds me of a video suggestion. Make a video of spray mig with .023(3 pass) wire on a 3/8inch steel fillet and bend-test with press and then comprare against 0.035(one pass) spray mig bend test. The leg and the throat - must be the same. I wonder the deeper "depth of fusion" of .035 wire would effect the break point. But i think this test would be invalid on fillet , because you can't get even leg and throad thickness between 3 pass weld with .023 wire and 1 pass weld with 0.35 wire. And this would effect bending. The best test would be to make it on a 3/8 plate groove weld and bend the root. Then the thickness would be the same. I wonder if the .023 spray mig would hold , because short mig definitely doesn't. And have a good day man. Edit: It's interesting topic because there's some 250amp chinese migs that states they can go to 24volts which is good of spray arc with .023wire.
That’s a good question. The biggest limitation of wire is its inability to fuse the root on anything thick without significant power, and preferably gas mix for spray. The different gas mixture combined with high values really solves most of the issues with wire over stick. .023 spray would open the door to possibly welding thicker plate with reduced settings that more lower powered welders could do. That could be a good thing in the sense of added capability, however I would be pretty hesitant to suggest doing it for the fact it would likely hammer the machine pretty bad and how well it would hold up would be questionable (depending on machine of course).
From a strength perspective believe it or not a 140a short circuit mig weld on a 3/8th fillet (like I use in many videos) will actually hold a full bend away from the face. The problem is it’s incredibly weak when bent towards the face due to less than zero root fusion. Such a weld would likely fail if it experiences vibration, dynamic loads, or force towards the face. Not to mention that weld would be even weaker on anything besides perfectly clean metal, I bet millscale would make it much weaker. Solid sidewall fusion and root fusion is always going to be an issue with c25 gas and short circuit on thick plate. C100 gas helps a ton but the welds seem to lose some strength over c25.
So realistically the main limitations of wire processes is output power and then gas mixture used. .023 wire with spray gas may actually be useable on a normal 200a mig welder for actual spray, but it would be at the limit. The results would have to be better than short circuit on 3/8th though. Next time I run .023 wire I will try it and see what happens.
@@makingmistakeswithgregThanks for the informative answer.
Your explanation was spot on. Can you tell me what kind of machine you would recommend that is of the newer inverter type that will hit the magic 25V min and allow me to spray arc with MIG(GMAW), stick weld up to 1/8”dia 6010 and TIG weld with high frequency for Aluminum on a 240VAC input? Would a MILLER MULTIMATIC 235 MULTIPROCESS fit the bill?
Thanks, keep up the great work. 😎
So the only welders that can tig aluminum and stick weld with 6010 are the everlast lightning, esab rebel 205, and the miller 220. The miller 235 is a DC only unit and for some unknown reason it not designed (and according to miller) won’t run 6010. Most all multi process machines won’t run 6010 because they have power supplies that can’t output more than 27-30v. The miller 255 will run 6010, and as of 6months ago miller updated the 220 with new software and hardware to run 6010. Whats interesting too, is my esab rebel 235 and rogue 200 actually run 6010 differently. So even from the same company there is differing performance on 6010 because of differing voltages the machine can output.
@@makingmistakeswithgreg Thanks for the reply Greg. The Miller 255 looks very nice, and only rated at just under 40A input at 240VAC at full rated output, that’s actually very impressive. However I’de probably have to rub my wife’s sore feet and back everyday for the next 25 years in order for her to buy me one. 😁👍
is it feasible for you to make aluminum skids for pressure washing setup?
Aluminum anything generally isn’t that hard to make, the material just costs a lot. It’s actually easy to work with in comparison to steel in a lot of ways. Are you looking for advice on how to make something?
@@makingmistakeswithgreg no, in a round about way was suggesting you could make, as there is a market for them in pw industry. Most seem to be made in the south, so you could corner market in your corner of the world, given your talent and entrepreneurial way.
@@charlottesspot gotcha. I am looking at buying a commercial building so I might consider starting to manufacture items of some sort. I will definitely have the room lol.
Makes me wonder how Fronius with the 180 can have it weld 6010 on 240 and 120 volts. I have done it just as a fun weld on plate.
It works. I usually run on 240 volts seldom 120 with any of my machines. The voltage /amp curves are interesting something most don't even think about. On stick I just set the amps and weld on mig I set the wire speed and trim volts ,never giving it much notice.
Then runnng on any synergic mode you just set thickness and weld again not paying any attetion to volts or amps. Thanks for the explanation Greg.
Is that the one that has a battery mode as well as a mains powered mode?
If so, it’s possible it’s drawing some extra power from the battery.
@@deltab9768 No mine are 120/240 volt models, not battery powered. Theydo have a battery powered one and Greg has one, just look at his previous video.
You can do a lot of crazy stuff with power electronics. If they have active PFC for example, the internal bus voltage after a ton of engineering will probably be around 400 V, regardless of 120 or 240 V input. Change the rectifier configuration between centertap and H with a relay etc. PFC boost stage does the rest. The control computer then decides how much power can be drawn safely and controls the welding inverter stage to a suitable curve. I have never designed a modern welder, but plenty of very similar systems. Some day i gotta design my own inverter welder, just so i can design my own hot start, "dig", variable inductance etc. features. Digital real time control is basically real world space magic.
Awesome comment zonkotron, and that’s what’s going on. By changing the voltage, frequency, and wave form going into the transformer, and having more control on the conversion of the transformer output they have complete control over output power. They are free to take the input wattage and split it into any number of varying output voltages and amperage setpoints. So the curve a normal transformer has becomes more or less a flat predictable line.
As far as the original question, fronius has absurdly high efficiency (over 90%) combined with power factor correction (and near perfect power factor. This is exactly why fronius can run 6010 at lower input voltages than any purely transformer machine could, because 95% of the available input wattage is turned into output wattage. A old transformer machine could run 6010 on 120v, but it would need 35-40amps of power to do it, which isn’t exactly practical. With that said I assure you the fronius is actually overloading the 120v breaker by a bit to achieve max output. It’s simply not possible to run a 6010 at 90 amps (90a x 30v = 2700 watt) on a 120v 20a circuit (2400watt) without overloading it. So the device will pull more power through the breaker than its face rating, and it can do so because the breaker trips on a thermal curve. Most 120v welders do this, however the fronius is unlikely to cause a breaker trip because its power factor correction is not letting reactive power back to grid through the breaker.
On a side note, the fronius accupocket battery welder I have is the only stick welder that is capable of 140a of output on 120v without overloading a breaker. That’s because the battery power reduces the power demand from the outlet. You can weld at 140a out for a 20% duty cycle on a 15a breaker and not trip it. Thats something that is not possible without energy storage like a battery.
@@makingmistakeswithgreg Hehe greg, i forgot to reply to the other answer you posted coupla weeks ago, too busy with my day job. Anyhow, we were discussing hardenability of mild steel. You seemed a little incredulous. No really. Sqare bar 1/2 inch (actually 12mm, im German) and similar sizes from my steel merchant, all of it will harden to a good chisel when quenched in an alkali solution (brine would probably work too, but the vapors cause rusting, no thanks, not in my shop). The reason is pretty clear. Carbon, by spark test, is on the upper end for mild steels. >.1 for sure. And copper, i got my hands on an XRF gun, is around 1%. Probably more Chromium etc than it really should have, as well, forgot the numbers. Copper was the shocker. All of it increases hardenability. Modern S235 European structural steel can have a carbon equivalent number of up to .35. Thats basically carbon plus all the hardenability increasers weighed by some formula. 35 points is not tool steel, but it is plenty to get massive strength increases on quench. Normally that should not be a huge problem, because a slow quench like a weld cooling in 2-3 seconds is too slow to get fully hard. And i also noticed that the structural shapes and flar bars from the same trader are not hardenable and spark less on grinding. Only square and round bars. I guess they roll the dodgy crap like vehicle scrap remelt into bars that dont usually dont get used for structural weldments anyways. Anyhow. Im a hobby blacksmith, power electronics engineer by trade and used to work part time as a machinist/millwright/museum assistant environment in an industrial heritage museum before i got my electronics degree. I have a "few" interests :D
As an electronics nerd this is pretty interesting.
I’m interpreting it as each machine setting comes with its own current/voltage curve.
Am I right in thinking a stick machine set to 100A would produce less than 100 if you were long-arcing and making a mess, and more than 100 if you stuck a rod to the workpiece?
So stick welding power sources produce constant current. 100amp setpoint means 100 amps regardless of arc length. As you long arc the rod the welder will handle the increase in voltage up until the cutoff of its volt amp curve. As the voltage increases due to arc length the power draw from the wall increases to be able to handle the demand. The increase in arc length increases heat input due to the wattage increasing, that combined with the long arc gap ends up causing the rod to become unstable and produce spatter.
With mig and wire processes, voltage is fixed and amperage is variable. Amperage is whatever it takes to keep the short clear (aka the dead short that short circuit mig produces). The higher the wire feed the higher the amperage because it takes more amperage to keep the wire from being shorted to the plate.
Every machine has a different volt amp curve, and some have multiple due to multiple transformers or multiple taps on a single transformer. Modern machines more or less mostly have a single curve and it’s often flat because the transformer inside is being controlled (for both frequency and waveform). The biggest limiting factor is input power. On 120v 20 amp circuit you only have 2400watts of power thus trying to run a 1/8th 6010 at 90a, 32v is 2880w, or way over. This is not counting the losses of the welder itself. How some welders are still able to run this is they overload the breaker and the machine itself is super efficient. The esab rogue in this video is 93% or higher efficient, and it draws up to about 30a on 120v. Therefore it’s possible for it to run 1/8th 6010 on 120v, something that is basically impossible to do on most welders.
So anyway constant current devices regulate current so you don’t just have a dead short and trip a breaker immediately or melt the rod. Constant voltage welders (wire welding) don’t regulate amperage output, the wire feed does. If you set the wire feed too high the machine will end up tripping its internal breaker/fuse (if equipped) or the outlet breaker.
@@makingmistakeswithgreg Thanks for the detailed answer! I think it’s helped me understand the voltage/current curves a lot better.
I don’t fully understand how they keep current constant at a set number across a range of arcing voltages. I can’t see how they’d manage that on the older machines that were just a transformer with taps or variable shunt inductance and no active electronics monitoring the output. But that’s not really relevant to the actual welding process!
@@deltab9768 Your concept of a welding transformer is too simple. A standard transformer has two winding and a laminated steel magnetic core. What determines the output is the primary to secondary turns ratio and the load. Generally it is a linear device. If you cut the load resistance in half you get twice the current.
But welding transformers are more complex. One method of controlling the current output is to vary the steel lamination in the core. Turning the current dial moves the core material in and out, altering the amount of core that supports the magnetic field. If you remove half the core material from the magnetic path then it can't transfer as much energy, it will limit the output.
@@rudycandu1633 That’s the variable shunt inductance I was talking about. It basically gives a “shortcut” path for some of the magnetic field to just run without entering the secondary winding. Effectively that would give the transformer some inductive reactance that “holds back” the current and (unlike normal transformer inductance) cannot be cancelled just by adding a load to the secondary.
That would obviously limit the current on the output but it wouldn’t create a constant current. It would still be affected by the voltage across the arc.