CV vs CC welding power supply for Arc Melting Furnace
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  1. #1
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    Default CV vs CC welding power supply for Arc Melting Furnace

    Ok, oddball question.

    I have a need to use a very large welding power supply for creating a stable arc. The arc is created in an inert atmosphere between a water cooled piece of copper and a tungsten electrode and the radiant heat melts samples such as platinum or rhodium. Thus far, I have been using my TIG welder, but I'd like more power...I'm at 300 A right now.

    I can pick up 650 A power supplies pretty cheap, but they are constant voltage...I've always had a rudimentary understanding that CV was for wire feed and CC was for TIG or Arc welding and that fundamentally it's transformer design that sets them apart. BUT...I have no understanding of whether or not a CV power supply will be able to maintain a stable arc for a relatively short period of time.

    In this application, the arc is started with a high frequency arc starter and then the arc length is kept relatively constant.

    Is anyone able to explain what the difference would be between my current, CC power supply, and a CV power supply.

    I just need power...and lots of it.

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    Quote Originally Posted by snowman View Post

    I just need power...and lots of it.
    Get one that switches between cv/cc

    FWIW The Meadville Pa craiglist has this for at least 6 months:
    MILLER SRS-1000-A1 3phase welder - tools - by owner - sale

    I can't recall if it is cv/cc switchable, the miller website has all the manuals
    online.

    Are you going to do any kind of magnetic stirring/focusing ?

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    Quote Originally Posted by digger doug View Post
    Are you going to do any kind of magnetic stirring/focusing ?
    Only that which exists naturally, or a little moving around of the electrode.

    The melt pool in these cases is only like 1/4" deep, so it's not like a crucible where you can end up with different densities and settling.

    Thanks for the link, I'll check it out!

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    A couple of months ago I got a tour of a "Melt shop"

    50 ton arc furnace, and a 100 ton remelting vacuum furnace next to it.

    Arc re-melt, with induction stirring, 2 wire feeders putting alloys in as needed,
    all under vacuum.

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    Yeah...that's just nuts.

    I'm already having trouble visualizing 1000 amps.

    It's scary.

    I like my piddly air cooled tig welding.

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    "maintain a stable arc for a relatively short period of time" is way too vague a description. how stable, and for how long?

    critical question, " the arc length is kept relatively constant" how are you doing that?

    the primary difference between CC and CV power supplies occurs as a short of the secondary is approached, a CC will "DROOP" in output, limiting the short circuit current (as say a stick electrode touches the work) and a CV will tend to spike (a necessary thing with a wire feed GMAW in short circuit mode). how you are adjusting the arc length in your application determines what will work for you I think. if you are doing this manually, a CC supply will be more forgiving. if you short a CV supply, you might get basically an "explosion" that will blow your melt away and destroy the electrode.

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    Next up...Snowman will be looking for a drive in movie's projector arc rod feeder...
    Last edited by digger doug; 02-21-2019 at 05:05 AM.

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    Quote Originally Posted by cyanidekid View Post
    "maintain a stable arc for a relatively short period of time" is way too vague a description. how stable, and for how long?

    critical question, " the arc length is kept relatively constant" how are you doing that?

    the primary difference between CC and CV power supplies occurs as a short of the secondary is approached, a CC will "DROOP" in output, limiting the short circuit current (as say a stick electrode touches the work) and a CV will tend to spike (a necessary thing with a wire feed GMAW in short circuit mode). how you are adjusting the arc length in your application determines what will work for you I think. if you are doing this manually, a CC supply will be more forgiving. if you short a CV supply, you might get basically an "explosion" that will blow your melt away and destroy the electrode.
    THANK YOU! This was the description I was looking for.

    The electrode is held mechanically, with manual adjustment on an as needed basis. Basically, the 1/4" tungsten is held in a copper rod that's about 1 1/4" in diameter, through a series of seals and a ball swivel. Nothing is moving around too easily.

    Arc Stability and length of time is around a minute or so.

    If I was doing a touch start, yes, I can see where the surge could cause an impressive explosion. Given that I had planned to use a high frequency starter, I don't see it as such. Generally you start your arc away from your melt, then move it closer to the melt...and I don't see a 1/4" tungsten electrode being "destroyed" in short order.

    I'll likely just use a CC power supply. I had not found one big enough, but Doug helped out with that. It's easy to shop for NEW, shopping for surplus, semi rare and mostly not in demand welder power supplies is a little difficult.

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    I have heard....That the sub arc people will wad up a steel wool pad and stick
    it in there to start the arc.

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    ^ honesly the ones i have been around you just start the flux and once you have enough flux to "submerge" you turn the current on then the wire feed.

    Bad shit happens only if you run out of flux! That said, i am talking 2x 1K amp power supplies on a twin head machine, either 1k amps to each or 2K to one and 1/4" wire with a seriously impressive deposition rate.

    As to destroying the tungsten, about the split secound after something blobs - spits up onto it.

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    The specific supply you're looking for, is a carbon-arc lamp supply. Look for Dalmatiangirl's Hanovia arc lamp supply, to see how it differs from a Hobart SRH-333...

    Miller SRH-333/Hanovia 3 Phase to Single Phase Conversion - SmokStak

    The SRH is a CV supply...


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