Ignoramus18456 wrote:

I can control the period of TIME when voltage is positive, or
negative, as percentage of the cycle.

That's what I meant.

I see. Glad that we agree then.

But this might also mean, that we are equaly ignorant. I'm not a
welding-pro.


Absolutely. I think (being a newbie to welding etc) that at 50-50
cycle, the amount od reverse polarity is excessive and leads to
overheating of tungsten electrodes, without any benefit. So it is good
to set cleaning (epecrode positive) to less than 50% of cycle.

I just had a look in my welding book (not that much about TIG power
sources in there). It says, that you get a diode (when welding Al, but
even with steel) due to the oxyde in the puddle. That is the reason for
having a DC offset (when welding with AC). It is there to compensate the
diode effect. The offset doesn't seem to be very high. From the diagram,
I guess about 30%.


I bought my welding machine for $9.99 on ebay:

I know, that's the reason for the "washing machine"


I also have pulsing.

Seems that pulsing is only used with DC. If you would use it with your
H-bridge, you should have to switch polarity in sync with the pulses.
Can you adjust the base current and the max current?


My welder is actually quite fancy, except for not
having AC. All digital, etc.

LOL! "Digital". You have thumb wheels with digits. But looking at the
wire nest in that machine, is is damned analog.


Nick
--
Motor Modelle // Engine Models
http://www.motor-manufaktur.de
DIY-DRO - YADRO - Eigenbau-Digitalanzeige