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Thread: TIG AC frequency and pulse interaction

  1. #1
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    TIG AC frequency and pulse interaction

    I've wondered for a bit about interaction between AC frequency and relatively similar pulse in TIG. If the two frequencies are very similar and the pulse duty cycle is ~50%, then it would seem to result in slowly shifting between one half of the AC wave (DCEP) and the other (DCEN). That would change the cleaning balance considerably. This shouldn't be a noticeable issue when the wave frequency and pulse frequency are quite different, but when they are close, the effect of two waveforms is to create a beat frequency (the difference between them), and it would seem that the balance would follow the beat frequency.

    Is there something I'm missing or is this just an uncommon enough situation that it is of no practical significance? I'm inexperienced enough that I rarely use pulse and have never tried it in the range of my AC frequency, but since the machine's capabilities overlap, it came to mind.

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    Re: TIG AC frequency and pulse interaction

    Think of pulse as having two settings HI and LOW in terms of amperage. How you set the machine will determine how much time you spend in the HI amp range followed by the LOW amp range per time interval and how many time intervals you have per second is your pulse rate.

    Your AC frequency is how often you go between DCEP and DCEN per second.

    If you think of it in the simplified terms you might see a clearer picture. In other words pulse is not going to change the cleaning frequency.

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    Re: TIG AC frequency and pulse interaction

    Iím not suggesting it changes the cleaning frequency. But it may affect the balance. Think of this: pulse and AC freq are perfectly synchronized. So if the low amps are 10% of the high amps and at 50% duty then the high portion will always be EP and the low portion EN (or vice versa). Of course they are not perfectly synchronized but, if close, a beat frequency modulates that effect.

    Probably not a practical concern, only theoretical.

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    Re: TIG AC frequency and pulse interaction

    Not sure I see the utility of pulsing at 60Hz or anywhere near it ... then again, I use a Syncrowave and CAN'T pulse that fast.

    Interesting question...seems like the mfgrs would have accounted for the phenomenon. Also, most of the machines that can pulse that fast can also change AC frequency, and it seems like a lot of the guys using those machines favor about 100-120 Hz for the AC freq, and again, I can't see why one would want to pulse anywhere near that fast.

    I'm sure some more knowledgeable folks will weigh in.

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    Re: TIG AC frequency and pulse interaction

    Quote Originally Posted by jwmelvin View Post
    Iím not suggesting it changes the cleaning frequency. But it may affect the balance. Think of this: pulse and AC freq are perfectly synchronized. So if the low amps are 10% of the high amps and at 50% duty then the high portion will always be EP and the low portion EN (or vice versa). Of course they are not perfectly synchronized but, if close, a beat frequency modulates that effect.

    Probably not a practical concern, only theoretical.
    I understand exactly what you mean. You are correct that it would end up affecting the arc waveform, in pretty much the same way Independent amplitude affects the arc. At that point might as well get a machine that has Independent Amplitude control.
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    Re: TIG AC frequency and pulse interaction

    Quote Originally Posted by Oscar View Post
    I understand exactly what you mean. You are correct that it would end up affecting the arc waveform, in pretty much the same way Independent amplitude affects the arc. At that point might as well get a machine that has Independent Amplitude control.
    Yes, it certainly wouldn't be a way to achieve independent amplitude control with any predictability. If the frequencies are not perfectly matched and the waves in phase, it wouldn't do at all what you wanted. Playing around a bit in a spreadsheet, I can see that the whole phenomenon is very sensitive to the various parameters, so it's not something likely to ever come up. Also as mentioned, the high pulse rates seem pretty uncommon. I know Jody has recommended ~30Hz pulse for some things, but I've not seen much, if anything, about 60-120Hz pulse. I imagine it has some use, since the machines do it...

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    Re: TIG AC frequency and pulse interaction

    Quote Originally Posted by jwmelvin View Post
    Yes, it certainly wouldn't be a way to achieve independent amplitude control with any predictability. If the frequencies are not perfectly matched and the waves in phase, it wouldn't do at all what you wanted. Playing around a bit in a spreadsheet, I can see that the whole phenomenon is very sensitive to the various parameters, so it's not something likely to ever come up. Also as mentioned, the high pulse rates seem pretty uncommon. I know Jody has recommended ~30Hz pulse for some things, but I've not seen much, if anything, about 60-120Hz pulse. I imagine it has some use, since the machines do it...
    I wouldn't be so sure about that.
    After working with them, it seems more like they dream up capabilities meaning that they have some idea... that in theory.... it may be beneficial.
    And then they stand back and watch what we can do with it.
    Just my opinion from my experiences. YMMV
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    Re: TIG AC frequency and pulse interaction

    I have tried pulsing on AC in every way possible, and all it does is take a high amp machine and turn it into a low amp machine. Considering all of the other options available I don't even bother.
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    Re: TIG AC frequency and pulse interaction

    Quote Originally Posted by FusionKing View Post
    I wouldn't be so sure about that.
    After working with them, it seems more like they dream up capabilities meaning that they have some idea... that in theory.... it may be beneficial.
    And then they stand back and watch what we can do with it.
    Just my opinion from my experiences. YMMV
    I am with you on this. I would bet they had no idea of doing what Mike Zancanato and Dave Powelson did with "Zank's Krazzee Idea". When I tried the Krazzee Idea I found cleaning to be sluggish until I raised the frequency above 250 hurtz, then the skin lifted right off. The wetting goes right to the root without excess penetration of the base metal. I use the Krazzee program on a lot of thin alum fillets now.
    Weld like a "WELDOR", not a wel-"DERR"
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    Re: TIG AC frequency and pulse interaction

    Quote Originally Posted by jwmelvin View Post
    I know Jody has recommended ~30Hz pulse for some things, but I've not seen much, if anything, about 60-120Hz pulse.
    The videos I've watched he has a kind of rule of thumb, 1-1.5pps, 33 pps, 133pps.

    He uses 133 pps a lot of thin/delicate stuff. It is what got me to use it on outside miter seams for tube.

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    Re: TIG AC frequency and pulse interaction

    Quote Originally Posted by TraditionalToolworks View Post
    The videos I've watched he has a kind of rule of thumb, 1-1.5pps, 33 pps, 133pps.

    He uses 133 pps a lot of thin/delicate stuff. It is what got me to use it on outside miter seams for tube.
    I think his pulsing is limited to DC.
    Weld like a "WELDOR", not a wel-"DERR"
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    Re: TIG AC frequency and pulse interaction

    Quote Originally Posted by shovelon View Post
    I think his pulsing is limited to DC.
    That could very well be. I only have DC myself. (hoping to fix that one day! )

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    Re: TIG AC frequency and pulse interaction

    Quote Originally Posted by TraditionalToolworks View Post
    That could very well be. I only have DC myself. (hoping to fix that one day! )
    Well hold onto your wallet. It's going to be a bumpy ride!
    Weld like a "WELDOR", not a wel-"DERR"
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    Re: TIG AC frequency and pulse interaction

    Quote Originally Posted by shovelon View Post
    Well hold onto your wallet. It's going to be a bumpy ride!
    That's been the case pretty much the entire time since I bought my inverter.

    I have spent way more money in tooling and accessories to be able to use it. Having space to weld in, being able to weld safely, having PPE despite the dolts I see all the time welding in t-shirts and tacking without gloves. Yes, I try to wear gloves, eye protection and cover myself from UV, use a quality AD helmet, etc...

    Some may criticize me and say I'm foolish with my $$$s, but everything I've acquired to use with the welder will be usable on other machines.

    So an AC machine will come in time, but it's certainly not a pressing issue. I've barely made my shop environment usable for the DC inverter I do have. This goes for acquiring a few angle grinders, getting a welding table setup (a certiflat coming to upgrade), clamps, magnetic tooling, etc...not to mention consumables...and argon gas as well (on my 3rd tank).

    EDIT: I will put my neck on the line and say that I have 1/3rd investment in inverter, 2/3rds in tooling, steel for projects, consumables, accessories, ppe, etc...and it probably wouldn 't be unwise to plan on 25% for inverter, 75% to other stuff. This is to say that your choice of welder is just the tip of the iceberg, don't forget about all the other stuff...buy the best you can afford.
    Last edited by TraditionalToolworks; 04-24-2018 at 07:08 PM. Reason: my $0.02 on allocating funds...

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    Re: TIG AC frequency and pulse interaction

    Quote Originally Posted by TraditionalToolworks View Post
    Some may criticize me and say I'm foolish with my $$$s

    This is to say that your choice of welder is just the tip of the iceberg, don't forget about all the other stuff...buy the best you can afford.
    Unless......you are using it to make money and you are already established. Then maybe it can go either way.
    Case #1 You only need the machine to do a specific task and it doesn't cost much to purchase.
    Case #2 You are going to use it for something you really will be learning as you go and the market is really bigger than you have opportunity with for the time being. Sort of the "build it and they will come" theory, only more like "buy it and you will see lot's more uses for it once you have it. You cannot use capability you didn't purchase.
    I see a lot of shops with only a 200 amp AC tig. Had they bought bigger (and better) they wouldn't be loosing customers to me
    I bought way way more than I could afford more than once. Then I welded my ever lovin' @$$ off !!! Paid for them and keep buying more toys
    That word of mouth snowball just keeps rolling and rolling.
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    Re: TIG AC frequency and pulse interaction

    Quote Originally Posted by FusionKing View Post
    Unless......you are using it to make money and you are already established. Then maybe it can go either way.
    Case #1 You only need the machine to do a specific task and it doesn't cost much to purchase.
    Case #2 You are going to use it for something you really will be learning as you go and the market is really bigger than you have opportunity with for the time being. Sort of the "build it and they will come" theory, only more like "buy it and you will see lot's more uses for it once you have it. You cannot use capability you didn't purchase.
    I like your analogy, and you have the type of welders I would like to have in my shop...even just a Dynasty 210DX would probably be fine for most of what I do.

    I pretty much fit both of those categories you list, just that I want better machines in my shop. The SW200 is a case in point though, I could probably be pretty happy with one of them, as long as it was reliable and my LWS would provide the service they've said they would. Pulse would be the only sacrifice.

    Quote Originally Posted by FusionKing View Post
    I see a lot of shops with only a 200 amp AC tig. Had they bought bigger (and better) they wouldn't be loosing customers to me
    You made me spit ice tea on my keyboard!

    And strangely, even though I'm not in a position to bid against you, I just want that type of equipment in my shop. My inverter really is a stop gap to cover #1 and #2 you list above.

    Alan

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    Re: TIG AC frequency and pulse interaction

    Quote Originally Posted by jwmelvin View Post
    Yes, it certainly wouldn't be a way to achieve independent amplitude control with any predictability. If the frequencies are not perfectly matched and the waves in phase, it wouldn't do at all what you wanted. Playing around a bit in a spreadsheet, I can see that the whole phenomenon is very sensitive to the various parameters, so it's not something likely to ever come up. Also as mentioned, the high pulse rates seem pretty uncommon. I know Jody has recommended ~30Hz pulse for some things, but I've not seen much, if anything, about 60-120Hz pulse. I imagine it has some use, since the machines do it...
    Just my ha'pennorth, if you're designing it to give variable a.c. frequency and variable pulse frequency it's pretty simple to synchronise the two - the pulse starts / finishes would be triggered by e.g. a.c. welding current going electrode-negative rather than having a free-running oscillator timing the pulses.
    But what do I know, I'm just an electronics tech. 😉

    Dave H. (the other one)

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    Re: TIG AC frequency and pulse interaction

    I try to minimize the amount of electronics in something that takes the kind of current and abuse that a welder routinely gets subjected to.

    It's kind of like, I dunno, minimizing the number of five-year-olds pedaling tricycles on the D.C. Beltway...just because you can do something, doesn't mean you should.
    Last edited by Kelvin; 04-27-2018 at 07:25 AM.

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    Re: TIG AC frequency and pulse interaction

    Quote Originally Posted by TraditionalToolworks View Post
    I like your analogy, and you have the type of welders I would like to have in my shop...even just a Dynasty 210DX would probably be fine for most of what I do.

    I pretty much fit both of those categories you list, just that I want better machines in my shop. The SW200 is a case in point though, I could probably be pretty happy with one of them, as long as it was reliable and my LWS would provide the service they've said they would. Pulse would be the only sacrifice.



    You made me spit ice tea on my keyboard!

    And strangely, even though I'm not in a position to bid against you, I just want that type of equipment in my shop. My inverter really is a stop gap to cover #1 and #2 you list above.

    Alan
    If you only knew how many times I have whipped out the plastic to pay for equipment only to go out and just kill it.
    My kids quote me back things I was going around saying out loud just to justify it. (years later)
    Things like "weeks pay in a day" and " I never got myself in a situation I couldn't weld my way out of"
    It gave them the vision (and guts) to go out and succeed in their fields.
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    Re: TIG AC frequency and pulse interaction

    I have tried all these settings on welders, but when it comes down to doing real work, I don't have time to set and try getting settings dialed in. So its set the amps to max use the pedal, set post flow to 10 and have at it. I turn off pre-flow, cause when I hit the pedal I want an arc now not later. If you learned with pre-flow then you are used to waiting on it.
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