Pulse VS AC Frequency control. Which does What??

[hooda]

So, I've been doing research for months and made the decision that the EVERLAST PowerTig 250EX fits the bill perfectly for what I'm looking for. Question 1. If all conditions were equal, and one were to set the pulse at 240 hz and the ac frequency at 120, and run a bead, then reverse the settings, what would be the difference?? The reason I ask is that most other machines at this price point (and beyond) don't offer anything close to the range of adjustability, just would like to know the benefits. PS when I get mine, I will opost pics so we'll all know

[performance]

Pulse has nothing to do with AC.
AC frequency changes the number of times a second the polarity changes
Pulse frequency changes the number of times a second the amp values change.

[Ram48]

Hooda
here is a link that will explain it .
http://www.weldingtipsandtricks.com/...-settings.html
He even uses a 250ex for the demo It will save you a lot of set up time especially if you are a NOOB like me

Ray

[dgarnier]

Pulse has nothing to do with AC.

ahh, not sure I follow - isnt pulse just switching the machine on and off at the given rate? and this can be dont in both AC and DC mode?

[hooda]

I guess what I'm getting at is that if the current is switching polarity 100x/sec and the pulse is going from, say 200 amps to 120 amps 200x/sec, that would mean that the pulse is at 200 amps for 1/2 of the wave on the plus, and 100 amps for the other half. if that was reversed, what would happen to the bead? I've looked at everything on the welding tips and tricks website, very informative. I guess I'd like to see someone on this forum post real world beads done with an EVERLAST welder. thanks.

4

[DiabolicZ]

I guess what I'm getting at is that if the current is switching polarity 100x/sec and the pulse is going from, say 200 amps to 120 amps 200x/sec, that would mean that the pulse is at 200 amps for 1/2 of the wave on the plus, and 100 amps for the other half. if that was reversed, what would happen to the bead? I've looked at everything on the welding tips and tricks website, very informative. I guess I'd like to see someone on this forum post real world beads done with an EVERLAST welder. thanks.

4

Here is me screwing around with all of the different options that my Everlast 225LX has using AC.


Here is an intake manifold I am making with it.

[DiabolicZ]

that would mean that the pulse is at 200 amps for 1/2 of the wave on the plus, and 100 amps for the other half. if that was reversed, what would happen to the bead?
4

What do you mean by "on the plus"?

Using the pulse on your welder... Lets take it down to 1 pulse a second to make it easier to understand what it is doing. If you have one pulse a second and you have it set at 200amps, then the hottest part of each pulse will be 200amps causing your metal to melt quick. On the LOW SIDE of the pulse, say you set it to 100 amps. Then the low side will allow the metal to cool but not below the 100amp you set it at. It goes through this cycle once every second.

This means that if you were able to move the torch perfectly even at 1/8" every second... then you would have a bead every 1/8" from the hot pulse. If you sped the torch up to 1/4" of movement every second, then you would have a bead every quarter inch if you were still set at 1 pulse a second.

Those are the most basic settings of your pulsing options on the 250EX. From there you can choose how much of that 1 second range is dedicated to the 200amp setting. For example, you can tell it to stay at 200amps for 75% of that one second cycle or 3/4 of a second. Then the remaining .25 seconds will be spent on the low side of 100amps.

Does that make a little more sense?

[DiabolicZ]

Now as far as the AC frequency you weld at... If you have ever welded aluminum before, using a AC, you hear a loud buzzing. Generally that loud buzzing is in the range of 110hz. This means that it is switching from DCEN to DCEP polarities 110 times every second. If you were to turn it down to 40hz, then it would switch polarities 40 times every second. Or up to 240hz it would switch 240 times every second.

What this does... A lower frequency will give you a wider welding bead. If you raise it to a higher frequency, it gives you a narrower welding bead.

None of this has any effect on pulsing and pulsing has no effect on your ac frequency. Both of them are separate functions.

[performance]

Hooda,

AC is cycling between polarity. We have a balance control on our machines which skews the concentration of time toward AC negative polarity, typically 70% of the time is spent in AC negative. And with the pulse we have a balance control that provides a constant ratio of time that the arc stays in the "low" stage of the cycle, as well. Also, with a square wave, its either on or off at full amps. Keep in mind you are not staying synchronized with the switching of the polarity either. I guess its theoretically possible to align the controls perfectly so that you create an amplitude control of the AC frequency, providing a separate amp level for the positive stage and negative stage of the AC cycle...which is what our ext units will be able to do as well digitally. But it would take fine tuning with a scope to create this scenario...But it would still weld, and weld well like this, if not better.

As a side not, there's not much to Jody's videos that isn't real world....There's several used in different situations.

[performance]

ahh, not sure I follow - isnt pulse just switching the machine on and off at the given rate? and this can be dont in both AC and DC mode?

No, pulse is cycling between two amperage levels, not turning the machine on and off.

[hooda]

So far, I've had the things I kind of knew explained (but better clarified, for which i thank you), and I've seen Jody's videos, which are what turned me on to EVERLAST in the first place. Here's 1 reason why I ask the question: My research shows that the 250EX has a wider range of adjustability of these 2 functions than most, if not all other manufacturer's machines in the same power category, regardless of price. That says nothing of the other features. I figure that a little more in-depth discussion might help others see the benefits. I still see room to expand on this, but it's late. Thanks again!

[hooda]

Let me try ro rephrase my question (these are the thoughts if an insomniac, so be patient with me)
First, Let's define parameters to keep the answer simple. AC balance at 50%. Amperage at 200 amps, pulse set at 50%.
That means that in 1/100 second:
1. if the AC frequency is at 200hz and the pulse is at 100hz, the polarity goes from dcen to dcep twice, and the amperage goes from 200 to 100 once.
2. if the AC frequency is at 100hz and the pulse is at 200hz, the polarity goes from dcen to dcep once, and the amperage goes from 200 to 100 twice.
Although I do not yet have a new EVERLAST welder, the curiousity of what the effect of this reversal will be intrigues me, as I can see dozens of uses for myself personally where being able to manipulate the arc characteristics will prove to be as important as the weld itself.

[performance]

Not that simple, you are leaving out the balance of the pulse or the actual time amount that the pulse stage(in our case on the lx,ex models it refers to the "drop" in current) is active during a complete cycle. Why complicate it to a 100th of a second, since we are not concerned what happens in that time length, only in seconds?
pulse and AC frequency are not related. It will actually help to compartmentalize the two things, and try NOT to think about how they interact.

Pulse has three adjustments: 1) Frequency, 0-500 hz (250ex) 2) Balance percent, (actual length of pulse half cycle) 3) And percent of welding amps.

AC frequency is the change in polarity. Pulse frequency is the change of amps.

[AussieChris]

These sketched waveforms is the way I see it. This is if the pulse and AC were exactly synchronised. They usually won’t be because the pulse timing is generated on a separate board to the AC and the timing circuits are not that stable. In any case it’s the average result over many cycles that counts.

oww...oww...oww...that makes my head hurt.
But I think you got the hang of it. You need to overlay the two to see the interaction directly.

[jakeru]

IME, increasing pulse frequency can have an effect on increasing arc "stiffness", whether it be in AC or DC welding mode. (Arc stiffness increase = makes the arc more "directional", or more focused, concentrates the heat closer to the tip of the tungsten and not letting it spread out as wide, helps to penetrate more deeply and can sometimes allow better control of the heat.)

I think many people aren't aware that high frequency pulsing can have this effect in A/C welding mode, because most machines that allow high frequency pulsing (only inverter power sources are capable) will also allow adjusting the A/C frequency, which is generally the more preferred method of arc stiffness adjustment in A/C welding mode. (A/C balance is another common adjustment that can also affect arc stiffness as well, with more with EN% (more penetration and less cleaning) = more "focused" setting.

I may have one of the machines that could prove to be an "exception" however, in that it supports high frequency pulsing (up to 300Hz) even in A/C mode, while it does not allow adjustable A/C frequency (A/C frequency is fixed at 60Hz on my Mosfet-based inverter machine.) 300Hz pulsing can be of benefit in A/C mode to noticeably increase arc stiffness over not using pulsing at all. The main drawback I find to using this feature especially for welding thick aluminum is, I can't run the machine "flat out" with average amps = max 200 amp output capability, because for the pulsing to function effectively, the current needs to be reduced below the peak capability of the machine.

[MuttonHawg]

hooda, I found this thread during a Google search because I, too, was curious how the adjustable A/C welding mode parameters interacted with the adjustable high-frequency (above a couple pulses per second). AussieChris, you drew exactly what I was suspecting, but I was more curious about what happens when the A/C and pulse frequencies match (or nearly match).

<I'm having trouble uploading the images for some reason - I'll try again tomorrow>

This is just a curiousity to me at the moment, but I created different versions of AussieChris' images to illustrate the point that performance stated - somehow magically aligning the knobs so that the A/C and pulse frequencies match. In this case, depending on luck of the draw, you could either end up with the high amplitude on the positive part of the cycle, or the negative, and no real way of knowing. Or, perhaps worse, if the knobs are something like 1/4 Hz off, you'll have a weird beat frequency interaction causing a swing from almost entirely positive-polarity pulses to almost completely negative-polarity ones on a 4-second cycle.

This seems unlikely, and probably a pathological case, but I tend to wonder 'what COULD happen'. I figure that as long as the A/C and pulse frequencies are even just a couple of Hz different, the beat frequencies will be relatively fast (a few times a second) and therefore will be fast enough not to really affect the weld at all. I would be very curious to know if the pathological case I described would actually affect the weld.

Sorry to resurrect this old thread, but I was curious!

[MuttonHawg]

Since loading images is working for me today, here's what I was referring to earlier:



I assume that with the analog dials, the same settings (if the AC and pulse frequencies lined up exactly) could yield either of these waveforms, and I assume they would give you different results welding. Is this the sort of thing you could do voluntarily with a digital TIG machine?

[jakeru]

Since loading images is working for me today, here's what I was referring to earlier:



I assume that with the analog dials, the same settings (if the AC and pulse frequencies lined up exactly) could yield either of these waveforms, and I assume they would give you different results welding. Is this the sort of thing you could do voluntarily with a digital TIG machine?

I've been studying the AC frequency and the pulse circuits in my Super200P a bit lately, and basically found that indeed, they operate completely independently of each other. This matches what I've noticed when playing with my pulse frequency on my Everlast Super200P machine (which has the A/C frequency fixed at 60Hz but the pulse frequency being adjustable (although not with much precision) up to ~300Hz.) So, you are correct in that the practical effect from similar running AC and pulse frequencies (they can even be off by an octave or other harmonic) is that you'll get those beating frequencies in the arc's sound and maybe noticeable in the way it flickers.

Theoretically, it could affect the welding arc like you describe but practically, it's not really achieveable. (And I think that even if you were able to achieve it once, it would be difficult to reproduce, so it not a useful feature.)

The digital AC/DC TIG machines I can think of generally seem to have watered-down pulsing in AC mode, with no high frequencies available (which are supported in DC mode only). Perhaps that's to avoid the kinds of unpredictable interactions like you've described.

There are a small number of TIG machines that allow direct setting independent EN/EP amplitude adjustment, and this would be a usable, and repeatable way of achieving either of the waveforms you illustrated above. Miller Aerowave and Dynasty350/700, Everlast 250EXT, and HTP Invertig 221 are the ones I'm aware of.