Welder/Generator THD problem

Discussion in 'The Garage' started by Navin, Oct 29, 2013.

  1. Navin

    Navin Long timer

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    Hey guys, been trying to get a fully mobile welding rig set up and just discovered THD, Total Harmonic Distortion is going to be an issue on my Miller welder. I'm set up to run it off a Harbor Freight 7,000W generator and am looking for a way to get THD down to 5% or less to avoid destroying the newer style control board in the Miller Matic 211.

    So, anyone know of a THD supressor or filter I can plug in? I have no idea how much THD the cheapo generator is putting out either, is there a way to measure it? I'm 99% sure it is too high regardless.

    Thanks for any advice and ideas.
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  2. Navin

    Navin Long timer

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    Trying to find info on UPS (uninterrupted power supply) options fror field use too. Anyone? Might just have to spring for a low THD generator. Not much info on getting a clean power from a cheap generator.
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  3. fxstbiluigi

    fxstbiluigi crash test dummy

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    Miller makes some really nice welding machines that also can be used for electrical power with a gas engine attached. No need for a seperate power supply.

    Why complicate things?
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  4. Navin

    Navin Long timer

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    I already own the welders, about $5,000 invested. Starting over is not the best option. I was lucky to read about THD before it bit me. I usually run on regular current, but need to get them portable when no outlet is available.
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  5. fxstbiluigi

    fxstbiluigi crash test dummy

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    Never heard of anyone using a setup such as you describe for portable welding.

    How old is your current welding equipment?

    Mabe it's time to sell or trade in what you have for a new, or used, portable machine that will do everything your current machines are capable of.
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  6. ttpete

    ttpete Rectum Non Bustibus

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    That generator probably puts out juice that's closer to a square wave than a proper sine wave. I don't think any kind of a filter would fix that.

    Only thing I can think of would be to get a welder that has no electronics, something like an older MillerMatic 35.
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  7. Navin

    Navin Long timer

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    Looks like a new generator with 5% or less THD is in the near future. They are out there, just wish I knew about this issue before buying the generator. Not that big of a deal but the specs on generators rarely give the THD number of the unit. Now I know it is a big factor for anything with a control board/computer controls.
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  8. broncobowsher

    broncobowsher Long timer

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    I would trust a better spec generator to run your high dollar welder instead of a filter to Band-Aid a sub-par generator into something that might not kill the welder.

    I would not recommend a filter.
    Either a better generator that makes good power, or a welder with a built in generator that was designed to work that way to begin with.

    Trying to run a UPS large enough to run that welder would end up costing more then doing a proper upgrade.
    How expensive is this board you are trying to save with how cheap of a filter?
    #8
  9. MKJ

    MKJ Married w/ Children

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    What type of service are you trying to perform? What type of market are you targeting? Construction? Equipment service?
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  10. MJS

    MJS Long timer

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    You'll need a generator that is rated at least 10,000 watt and somewhere around 20HP. That will give something around 8,000+ watts continuous or around 35 amps at the 230-volt receptacle. A good Honda gen is this range is approx $5,500, maybe $4,000 for a house brand import. For that much money you can get a Bobcat 250 engine driven welder. Add a wire feed unit and you can do everything with one machine. Including power your 211.

    One of the things that may "get you" with a separate generator is the generator engine speed and capacity to handle sudden loads. The engine driven welders all spin up to speed at first contact and maintain a steady engine rpm. My modern portable generators seem to adjust their engine speed based on load. This may have an detrimental effect when trying to strike an arc with the 211 if the generator can't pick up the increased load quick enough. And a welder is a big load.

    PS: I would stay away from the Bobcat 225 if you think you might do any heavy welding. The machine we had was just short of the power and stability needed to run a 1/16" structural wire. Ran stick fine though. Replaced it with a Ranger 305 that takes everything we throw at it.

    I know you said you were already invested in the 211 but if you really need to go portable then it is cheaper to buy the right tool for the job. Just my $.02

    Cheers
    #10
  11. Navin

    Navin Long timer

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    The value of the control board IDK, but if it bugs out in the middle of a big job I can lose more $ anyway. I'm not interesred in frying board after board either, how many spares would I need to carry? One bad shot could keep frying them over & over.

    The Harbor Freight gen pushes it fine, and I'm doing fine grade RV to marine to hot rod stuff.

    The low THD gen is cheap enough at $1200 so not a big deal to protect my stuff and continue to be portable. If there was a filter/inverter it might still be the best option to get the new gen, just fishing for info.

    Thanks.
    #11
  12. Navin

    Navin Long timer

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    Problem solved with a new Troy Built 8000w generator for $899 at Lowes, and a 10% coupon. Under 6%-3% THD is far better than the maybe higher than 30% of the Harbor Freight cheapo unit.

    If you are gen shopping for the house where TVs and everything else prefers clean electricity to preserve the control boards, this one looks to be the cheapest and cleanest one readily available.
    #12