Welding Tips and Tricks

On the tipsandtricks.com WEB site there is an article entitled:

AC Waveforms and Advanced AC Tig at https://www.weldingtipsandtricks.com/ac ... pulse.html
In that is a diagram representing Advanced Pulse that is not clear on where the AC waveform is with respect to zero volts. I have edited that diagram - is it correct?
This shows a DCEN base voltage that is periodically interrupted with an AC voltage with 50% balance. The 50% is probably unrealistic but easier to draw with paint.

I realise that I don't need to know these details to weld but I am curious.

Thanks
Jack

Your question is about volts but your diagram is showing amps.

BugHunter wrote:Your question is about volts but your diagram is showing amps.

There might be a slight phase difference because of the reactance of the arc but the waveforms will be the same shape.

I am asking if the low current DCEN section is simply interrupted by a periodic but otherwise typical AC TIG current. Is the average AC current during the AC section zero (as in my drawing) or equal to the DCEN current?

Alternatively, substitute current for voltage in the original question.

Jack

Jack Ryan wrote:

BugHunter wrote:Your question is about volts but your diagram is showing amps.

There might be a slight phase difference because of the reactance of the arc but the waveforms will be the same shape.

I am asking if the low current DCEN section is simply interrupted by a periodic but otherwise typical AC TIG current. Is the average AC current during the AC section zero (as in my drawing) or equal to the DCEN current?

Alternatively, substitute current for voltage in the original question.

Jack

Yes you have that correct, that is the basic premise for that kind of operation. The initial diagram can be thought of as a simplistic depiction of what happens, which is as you have mentioned: there is a typical AC TIG operation and the machine sneaks in a DCEN output periodically. It doesn't have to be lower in absolute magnitude compared to the AC waveform as the picture suggests, but it can be. It could very well be the same magnitude. The advantage being that once the AC waveform cleans/etches the aluminum, the DC component will have no trouble creating excellent penetration because the otherwise problematic oxide layer is no longer present.

Oscar wrote: Yes you have that correct, that is the basic premise for that kind of operation. The initial diagram can be thought of as a simplistic depiction of what happens, which is as you have mentioned: there is a typical AC TIG operation and the machine sneaks in a DCEN output periodically. It doesn't have to be lower in absolute magnitude compared to the AC waveform as the picture suggests, but it can be. It could very well be the same magnitude. The advantage being that once the AC waveform cleans/etches the aluminum, the DC component will have no trouble creating excellent penetration because the otherwise problematic oxide layer is no longer present.

Thanks Oscar. I didn't want to end up like the cat (the one curiosity killed) but the manufacturers and the Internet generally tends to gloss over such details.

Regards
Jack