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  1. #1
    Join Date
    Nov 2020
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    Default Mig Welder for Generator Power

    Hi Guys,
    I have just joined and live on a remote property, have been welding on a portable 8Kva petrol generator with a transformer type Arc (180A) for the last 25 years, am looking to get a single phase gas Mig (150-180) to do light gauge stuff, and maybe Aluminium at a pinch.

    Question is, What is available that people recommend?

    There seems to be a tendency towards Inverter machines, which are useless to me, and it seems hard to find a basic transformer type with knobs and minimal electronics/LED displays, any advice from someone in a similar situation,

    Thanks.

  2. #2
    Join Date
    Aug 2011
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    Melbourne
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    Hi there,

    Cant really help with your question as its outside my area of expertise.

    I am keen to understand why an inverter welder is not an option for you.

    Simon

    Sent from my SM-G970F using Tapatalk
    Girl, I don't wanna know about your mild-mannered alter ego or anything like that." I mean, you tell me you're, uh, super-mega-ultra-lightning babe? That's all right with me. I'm good. I'm good.

  3. #3
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    bought a AVR generator, 8.5 Kva, and a BOC smootharc mig/tig/arc inverter welder new several years ago, as a package that was supposed to work for me, welder lasted at best, 10 hours before destroying itself and needing to go back under warranty, upon return it lasted 2 hours, this time when it went back, the repair guy said to never run it on a generator again, voltage and hertz control need to be precise for inverter type welders, any fluctuation will cause nearly all to fail, unit has sat in the shed for 5 years and never used again, not going down that path again, and against the advice of the guy who has a trade in repairing them.

  4. #4
    Join Date
    Jun 2010
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    Canberra
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    Default

    That's a shame inverter welders typically don't care at all about voltage or frequency, as it immediately gets turned into DC inside the welder. That said, it could be that the voltage swing from the AVR on your generator may have caused issues - as the voltage drops due to increased load (striking an arc) an inverter will simply draw more current as needed to maintain the required input power (volts x amps) so if the AVR is a bit slow, and allows the voltage to momentarily drop to, say, 50V, the input current might momentarily go from 20A to 100A, perhaps exceeding the rating of the input rectifier.

    Finding a decent, new transformer-based welder is going to be hard. It might be worth seeing whether there are any inverter units that specify compatibility with generators.

  5. #5
    Join Date
    Nov 2017
    Location
    Geelong, Australia
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    Default

    You might find this blog article on the Weldclass website interesting in regards to the issues with running inverters off generators.
    https://www.weldclass.com.au/blog/47...tions-answered

    Some interesting stuff that I wasn't aware of like disconnecting the welder from the generator before starting/stopping. Makes sense when the reasons are explained.
    Also the normal thing regarding voltage drop in extension leads (ie use H/D leads and keep them as short as possible).

    Obviously Weldclass are saying their own gear is designed to be suitable for generator use, but I'm sure there are other brands that will be too. Inverter welders are the perfect thing from a mobility perspective and I'm sure there are thousands in use running happily off generators.

    The repair guy that told you never to run yours off a generator, if you still have access to him it would be worthwhile asking him for a recommendation on a make/model that he knows will work successfully.

    I have no experience with the BOC welders, but my impression from the general comments online is that they aren't necessarily the quality level that you might expect from a dedicated welding supplier like BOC.
    It would be worth giving the likes of Tokentools a call to discuss your situation. They have been around a fair while and all the feedback I've seen about their service and welders has been positive. Being a smaller company offering long warranty on their gear if you explained your situation I think they would be unlikely to steer you in the wrong direction.

    Also keep in mind that there's the standard consumer protection in that if you state you're going to run it from a generator, and the supplier sells it as being suitable you don't have to just suck it up if its not.

    Edit: Apologies for not answering your specific question on sourcing a transformer MIG. The last time I recall seeing one for sale new was old stock, and in the 200-250A range with the matching ~90kg weight to go with it. You'd probably be looking at having to get a used one.

    Steve

  6. #6
    Join Date
    Aug 2008
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    near Rockhampton
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    The Cigweld Weldskill 250 might still be a transformer machine. https://www.totaltools.com.au/80727-...plant-w1004500

    I have a Cigweld Transmig250SE and it has performed really well. I also have a Unimig 250 amp MIG, TIG, Stick and it's performance leaved the older transformer welder for dead, it produces a better arc and is much more efficient, so you get more electricity into the arc, then is lost as heat in the machine, but then being electronic it is more fragile.

    There are not many choices left these days for transformer ones. I am not going to recommend any inverter ones

    Here is a WIA transformer one https://www.welding.com.au/equipment/view/weldmatic-270

    You are not going to get full 250 amps power out of them with only 8.5KVA though. You need about 12kva for that.
    Gold, the colour of choice for the discerning person.

  7. #7
    Join Date
    Dec 2018
    Location
    NSW
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    Quote Originally Posted by RustyArc View Post
    1) That's a shame inverter welders typically don't care at all about voltage or frequency, as it immediately gets turned into DC inside the welder.

    That said, it could be that the voltage swing from the AVR on your generator may have caused issues - as the voltage drops due to increased load (striking an arc) an inverter will simply draw more current as needed to maintain the required input power (volts x amps) so if the AVR is a bit slow, and allows the voltage to momentarily drop to, say, 50V, the input current might momentarily go from 20A to 100A, perhaps exceeding the rating of the input rectifier.

    Finding a decent, new transformer-based welder is going to be hard. It might be worth seeing whether there are any inverter units that specify compatibility with generators.
    In my experience, true on all 3 accounts. Generally it looks something like Input filter>rectifier>PWM/control circuits>inverter>transformer>rectifier>DC output
    Transformer machines are dinosaurs- outdated by 25 years or more. Generally worth more in scrap copper than they are as a welding power source (change my mind).

    If you examine the machine's data plate, or manufacturer's specs, it will identify the voltage and voltage tolerance of the unit. ie 240V +/- 30%. The max current draw on the input circuit should also be listed. NB this input current spike is short lived, but often much higher than the input circuit fuse... machines with a 15A input plug can momentarily spike up to 30A.

    Generators by nature essentially turn a combustion engine into rotational energy which drives an AC generator. When a welder arc is struck at say 150A output (welding current- ie a 4mm arc welding rod), and it draws an instantaneous 23A from the input circuit, this tends to do odd things for a mechanical engine that is struggling to handle all the electrical 'load' on the generator windings, while maintaining it's RPM and voltge output. This is my understanding of where things go AWOL on a generator, when the input requirements for a welder are not met by the generator. Just like an ECU on a car, without a minimum voltage available to the machine, it won't play the game. Same would apply for a transformer machine- what you get out of a welder is a function of what you put into it- welders are just a 'gearbox' for power from a wall socket at 240V 15A, to welding output at 23V, 180A or similar...

    I run a single phase german designed/built pulse mig that is good for steel as well as aluminium (and stainless, FCAW, Silicone bronze), and is rated for 230V input -40% and +15% ie can operate safely at full output between 138V and 264V- well within the specs of a dodgy farm supply at the end of the power line. Specs suggest it can be run on an 8kVA genny, but I haven't tested it out on one.

  8. #8
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    Dec 2018
    Location
    NSW
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    Quote Originally Posted by OxxAndBert View Post
    You might find this blog article on the Weldclass website interesting in regards to the issues with running inverters off generators.
    https://www.weldclass.com.au/blog/47...tions-answered
    Got to love the poorly photo-shopped welder into the pic of their article!
    I wonder which brand machine was in the pic before they cropped their own welder in...

  9. #9
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    Nov 2020
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    thanks guys, some good info there, especially the bit from weldclass and generator use,
    looking at 180 being absolute max I can run on the generator I have, even though their machines are setup for use on a generator, they still say it only minimises the chance of electronic failure.

    Will have to scroll through specs of the myriad of inverter machines and see who warranties use on a generator, betting not many.

    My mate did get an ESAB many years ago, cost him $6000, ran it on a 12Kva diesel generator, lucky for the warranty, as it had to be rebuilt 7 times over its life, at the end they gave him a brand new machine which he now runs on an 18Kva diesel generator with complete voltage and hertz regulation, no problems since.

    Unfortunately I need something portable that I can load into the back of the ute by myself.

    The guy that repaired them said that not only did the voltage have to stay within set guidelines, but that it was critical that the hertz was smooth as well for inverter machines.

  10. #10
    Join Date
    Sep 2010
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    Lebrina
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    Quote Originally Posted by BayanDundee View Post
    bought a AVR generator, 8.5 Kva, and a BOC smootharc mig/tig/arc inverter welder new several years ago, as a package that was supposed to work for me, welder lasted at best, 10 hours before destroying itself and needing to go back under warranty, upon return it lasted 2 hours, this time when it went back, the repair guy said to never run it on a generator again, voltage and hertz control need to be precise for inverter type welders, any fluctuation will cause nearly all to fail, unit has sat in the shed for 5 years and never used again, not going down that path again, and against the advice of the guy who has a trade in repairing them.
    You've identified your problem right there. BOC Smootharc. I am yet to see a decent BOC Smootharc of any description and their build quality is absolute rubbish. Cheap Inverters often struggle with generators, but decent Inverters thrive on gensets. Worth remembering too is that cheap gensets often overstate their capabilities.

  11. #11
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    Quote Originally Posted by Karl Robbers View Post
    You've identified your problem right there. BOC Smootharc. I am yet to see a decent BOC Smootharc of any description and their build quality is absolute rubbish. Cheap Inverters often struggle with generators, but decent Inverters thrive on gensets. Worth remembering too is that cheap gensets often overstate their capabilities.
    have had a better look around, seems there is some advancement in technology since initial purchase which makes inverters better able to handle power fluctuations, along with a reduction in price, warranties are poor but the 180A Unimig machine seems to be the pick of the smaller machines with the best warranty for gen use I could find.

  12. #12
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    If you are going to run off a generator, I personally would only buy one with power factor correction. I have seen the difference.

    Unimig machines often say only for use on pure sine wave generators. Although any good generator with AVR and brushes should have a good sine wave. With a total harmonic distortion (THD) below 5%.

    Here is a good thread showing cheap inverter stuff and generators.

    https://metalworkforums.com/f309/t203231-generator-waveforms


    http://power-topics.blogspot.com/2008/02/what-is-pfc-and-why-do-i-need-it.html
    Gold, the colour of choice for the discerning person.

  13. #13
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    Update for those interested

    Have been to see the bloke who does all the repairs up this way, he says that when it comes to inverter welders and generators, he can only recommend Kemppi as being the only reliable one, it is a pricey one with power correction of 0.99%.

    The main welding supply shop now deal with Kemppi as a preference due to failure of other machines. Their advice was that Lincoln still make a 180a coil based mig and it would be the best option to get one of these, either new or used.

    They also told me that it is not advisable to go to a higher amp model in an inverter to get a better power correction factor, say a 220 and only run it at 160, as some models will sense the available power supply, and if it is not suitable to run at full amperage it will throw an error code and not operate anyway.

    Seems the best option is still old school tech in my position, anyone know of a good 2nd hand buy/swap/sell site specialising in welding equipment I can keep an eye on for a Lincoln mig?

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