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  1. #1
    Join Date
    Aug 2008
    Location
    near Rockhampton
    Posts
    5,950

    Default My welders are breeding.

    It seems my welders are breeding.

    Some weeks ago at an online auction I bid on and won a Miller Thunderbolt 300 amp AC stick welder. It is a welder that is single phase, but is 240V or 415V input. It also came with a heap of welding rods and I have found I like 7014 rods. It will probably get converted to running a lathe, as I can input 240V and tap 415V off it, then use that to run a VFD connected to a lathe.

    Then I go out and buy a portable Unigmig 250MTS for mig welding in the field. It seems really good and probably is the best welder I own going by the arc it runs. It also seems to be highly efficient as turn the stick up to full power and I can burn holes in everything, all from a 15 amp socket, although it says to use a 32 amp.
    Gold, the colour of choice for the discerning person.

  2. #2
    Join Date
    Aug 2011
    Location
    Melbourne
    Posts
    4,396

    Default

    Hi RC,

    What a problem to have!

    Wrt using your welder as an step up converter (is that what you would call it?)

    I have an old Goodwell AC arc welder which has multiple input taps, 240 & 415 from memory. Are you suggesting it may be possible for me to wire that to get 415 out of a 240v input?

    (Hey Mods time for the massive disclaimer bit!)

    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
    Join Date
    Mar 2011
    Location
    Adelaide
    Posts
    409

    Default

    Quote Originally Posted by simonl View Post
    Hi RC,

    What a problem to have!

    Wrt using your welder as an step up converter (is that what you would call it?)

    I have an old Goodwell AC arc welder which has multiple input taps, 240 & 415 from memory. Are you suggesting it may be possible for me to wire that to get 415 out of a 240v input?

    (Hey Mods time for the massive disclaimer bit!)

    Simon

    Sent from my SM-G970F using Tapatalk
    If it has seperate windings for the 415 and 240 depending on how itís wound and assembled, yes it might be possible. The two input windings would need to be assembled onto the core in the same fashion as the traditional primary and secondary relationship between input and low voltage secondary are. So assuming they were, you also need to keep in mind the voltage vs current relationship that applies when using a transformer which is in this case as itís a step up, as voltage ones up, available current goes down. Your step ratio is 1.7:1 so if you want 10A at 415V the 240V Side must be capable of delivering 17A plus any losses, which in an iron core transformer will be anywhere up to 30%, so you could comfortably suggest around 23A would be required at the input winding.
    More likely the input winding is a tapped winding in which case no it is not possible.

  4. #4
    Join Date
    Nov 2017
    Location
    Geelong, Australia
    Age
    53
    Posts
    1,087

    Default

    If the inputs are a single tapped winding it will still work. Itís effectively an auto transformer.

    Steve

  5. #5
    Join Date
    Dec 2018
    Location
    NSW
    Posts
    298

    Default

    Know them feels.
    Nothing quite matches new welder day IMO.

    Picked up my new one last week myself. A German 180a multi process pulser by EWM. One of the nicest arcs I've had the pleasure of making to date. Particularly so as a single phase machine.

  6. #6
    Join Date
    Aug 2009
    Location
    East Warburton, Vic
    Posts
    337

    Default

    Quote Originally Posted by .RC. View Post

    Then I go out and buy a portable Unigmig 250MTS for mig welding in the field. It seems really good and probably is the best welder I own going by the arc it runs. It also seems to be highly efficient as turn the stick up to full power and I can burn holes in everything, all from a 15 amp socket, although it says to use a 32 amp.
    Iíve got one of these as well, heaps of power and yeah, itíll blow holes everywhere if you not concentrating or turn it up too much
    Cheers

    DJ

  7. #7
    Join Date
    Aug 2008
    Location
    near Rockhampton
    Posts
    5,950

    Default

    Quote Originally Posted by simonl View Post
    Hi RC,

    What a problem to have!

    Wrt using your welder as an step up converter (is that what you would call it?)

    I have an old Goodwell AC arc welder which has multiple input taps, 240 & 415 from memory. Are you suggesting it may be possible for me to wire that to get 415 out of a 240v input?

    (Hey Mods time for the massive disclaimer bit!)

    Simon

    Sent from my SM-G970F using Tapatalk
    This welder has three input leads, a neutral then one for 240 and another for 415. When it is wired for 415, the cooling fan runs off the 240V wire and neutral. Mine is essentially an auto transformer, not an isolating transformer.
    Gold, the colour of choice for the discerning person.

  8. #8
    Join Date
    Mar 2011
    Location
    Adelaide
    Posts
    409

    Default

    Quote Originally Posted by OxxAndBert View Post
    If the inputs are a single tapped winding it will still work. Itís effectively an auto transformer.

    Steve
    Valid point, wasnít even thinking about an auto transformer when I was typing this morning.

  9. #9
    Join Date
    Aug 2011
    Location
    Melbourne
    Posts
    4,396

    Default

    Thanks for the replies.

    So the welding connections don't get used. They basically become a spectator winding?

    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.

  10. #10
    Join Date
    Oct 2008
    Location
    N.W.Tasmania
    Posts
    1,167

    Default

    Quote Originally Posted by simonl View Post
    Thanks for the replies.

    So the welding connections don't get used. They basically become a spectator winding?

    Simon

    Sent from my SM-G970F using Tapatalk
    That's correct Simon, at least on any 240/415 Volt input welder I have seen. The primary winding is effectively an auto transformer, so you get no isolation, but a lot less copper is needed to wind the winding, than would be the case where you had two seperate windings, electrically isolated but magnetically coupled. I have often wondered if they could be used to build a rotary phase converter, but have felt that I would probably need a conventional transformer, that is one with seperate windings for the 240 volt winding and another winding for the 415V. It seems to me that with the Australian system having the neutral leg at ground potential, I would never get that leg to get anywhere near 415v without having an isolation transformer to get my 415 volts. That won't be a problem for Richard however if he uses a VFD to generate the three phases, and since VFDs are so much cheaper now and come with lots of useful features, the attraction of a rotary phase converter is lessened even though it can run multiple machines simultaneously.

  11. #11
    Join Date
    Aug 2008
    Location
    near Rockhampton
    Posts
    5,950

    Default

    Gold, the colour of choice for the discerning person.

  12. #12
    Join Date
    Jan 2004
    Location
    Mackay North Qld
    Posts
    5,399

    Default

    Quote Originally Posted by simonl View Post
    Hi RC,

    What a problem to have!

    Wrt using your welder as an step up converter (is that what you would call it?)

    I have an old Goodwell AC arc welder which has multiple input taps, 240 & 415 from memory. Are you suggesting it may be possible for me to wire that to get 415 out of a 240v input?

    (Hey Mods time for the massive disclaimer bit!)

    Simon

    Sent from my SM-G970F using Tapatalk
    OK ! Here it is,then.


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    Members following such information do so at their own risk

  13. #13
    Join Date
    Aug 2008
    Location
    near Rockhampton
    Posts
    5,950

    Default

    Well there is one downside to this Mig, stick, Tig welder.

    They decided to put something called Voltage Reduction Device on the stick setting. I have renamed it to make rods stick device.

    An absolutely stupid thing to have without a switch to turn it off. The whole point of welders OCV is to make it easier to strike the arc.
    Gold, the colour of choice for the discerning person.

  14. #14
    Join Date
    Aug 2011
    Location
    Melbourne
    Posts
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    Default

    Yea I learnt about that feature when looking into my last stick welder purchase.

    Is it designed to reduce the chance of electricusion of the operator if they touch both the clamp and electrode end?

    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.

  15. #15
    Join Date
    Dec 2018
    Location
    NSW
    Posts
    298

    Default

    IIRC the OCV on non vrd welders can be up around 60V. Some electrodes will specifiy a minimum OCV for operation.

    VRD IS a protection device.
    It is often required for workplace environments where it is a WHS requirement. They usually have a protection rating that is linked to the type of environment they are able to be used in from a WHS risk management point of view- category A B or C (cat c is when the operator is in contact with the job, and temp > 35 degrees c- ie climbing all over the job in hot summer heat). I can't recall the actual requirements of the australian standard, but having the ability to switch it off may mean that the manufacturer is no longer compliant to the standard.

    YMMV if all this is applicable for you, as with most things... But the big idea is to stop you copping the full 200A and popping your eyeballs if you are somehow stupid enough to put yourself as the path of least resistance between the earth clamp and the electrode holder...

    That being said, an AS1674 compliant VRD will give you full voltage within 300ms of arc strike. I'd suggest you either have incorrect electrode selection, or a slow non compliant VRD. Or perhaps all the pipeline, mining and field service structural guys who need to use a VRD machine for work are also having the same problem getting a rod to strike?

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