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Thread: Looking for some help understanding OCV's

  1. #26
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    Re: Looking for some help understanding OCV's

    Quote Originally Posted by farmersammm View Post
    Might be an oldie, but it was actually a goodie. I ordered the Lincoln Handbook of Arc Welding and Design offa Ebay because of it. I have the Bible, but I thought, after seeing the reference to this book, it would make a nice addition.
    No doubt it’s a goodie, would probably still work today LOL.

    What other book are you referring to Sam? I always thought the welding “bible” was the Lincoln Handbook?

  2. #27
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    Re: Looking for some help understanding OCV's

    Without trying to understand all the information above......and injure my brain in the process:
    A specification of a inverter TIG reads: “Open circuit voltage (VRD active). <113V”
    Is that good/bad? Obviously I don’t get it.
    Ernie F.

  3. #28
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    Re: Looking for some help understanding OCV's

    Quote Originally Posted by metalman21 View Post
    Without trying to understand all the information above......and injure my brain in the process:
    A specification of a inverter TIG reads: “Open circuit voltage (VRD active). <113V”
    Is that good/bad? Obviously I don’t get it.
    I'm surprised it is so high. I had been led to believe shock hazard concerns forced manufacturers to lower OCV.

    Older machines commonly had 100 OCV. falling to less than half that when an arc is struck.
    What little I understand of this limitation is what makes new inverters not work well with 6010 rod. It needs more voltage to get started.

    Think of automobile ignition. A 12 volt system wouldn't give much spark. Model T Ford ignition was low in the thousands, and was plagued with non fires.

    Slightly newer vehicles got into the 6000 volt range at the sparkplugs. Still they were fussy.

    Now spark ignition is 60,000+volts.

    Same is true with stick welders, and TIG welders. Low OCV makes it challenging to light up some rod varieties. Meanwhile, safety people want low OCV for safety to limit shock hazard.
    Last edited by Willie B; 22 Hours Ago at 10:15 PM.
    An optimist is usually wrong, and when the unexpected happens is unprepared. A pessimist is usually right, when wrong, is delighted, and well prepared.

  4. #29
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    Re: Looking for some help understanding OCV's

    Quote Originally Posted by Willie B View Post
    What little I understand of this limitation is what makes new cheap inverters not work well with 6010 rod. It needs more voltage to get started.
    Adjusted it for ya.
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  5. #30
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    Re: Looking for some help understanding OCV's

    Quote Originally Posted by Willie B View Post
    I was an annoying kid, "Why Daddy, Why? Now, I'm an annoying old man, "WHY?" If amps remain the same, and voltage increases, we get more heat. Longer arc length gives more resistance. In a series circuit, any point of resistance gets a bigger share of voltage. I've never been clear if a long arc, meaning more voltage means less amperage. Either way, more volts, longer arc will compound into much more voltage.

    Thinking out loud, I don't pretend it is fact; Does the short arc used with lower voltage also push a bigger share of the heat into the weld joint for more penetration? If burn off of electrode rate increases, deposit rate must increase. In the sense that dabbing filler, converting solid to liquid consumes BTUs, does this chill the weld metal already deposited?

    I envy those of you with SA-200 and similar machines. You control voltage with governor speed. Can this be controlled on a Miller Bobcat 250? I suspect higher range, with little fine amperage does this. I have no crisp, or soft control like Fieldres shows on his modern Lincoln.

    Willie
    I have done some serious testing in this area. When you increase ARC length your voltage goes up causing a very hot-plasma to be created, which causes resistance, which lowers amperage however, you are getting the wattage as you mentioned. That is how I used to weld very thick aluminum using straight DC current through helium. Anyone that has welded aluminum knows you cannot just deeply penetrate very thick aluminum with your TIG welder, with argon, in AC, or DC straight polarity, but if you use pure helium and straight DC current you can. There is also something going on with the plasma itself and the rays created that make that possible but that is another thread that will get me banned. If you have welded with 7018 and 7016 you know that the 7018 rods will weld with fewer amps than the 7016 rods. Both are supposed to be the same material filler-wise, but they weld totally differently at the same amps. My guess is that the iron powder is mixing with oxygen and creating heat, but that is just a guess.



    Sincerely,

    William McCormick
    If I wasn't so.....crazy, I wouldn't try to act normal, and you would be afraid.

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