mike wrote:


Thanks for the links. I like to learn new stuff.
I'm still trying to get my head around why the graphs in the first
link are reversed in time,


** Figures 3 & 4 showing scope screens have been published up side down so need rotating by 180 degrees.


but if I stand on my head, it looks
like the drive signal is optimized to maximize inrush current.

** By simply switching the AC supply on at zero volts.


I don't have any argument with that. You can certainly manage
the drive so the core saturates.


** By simply switching the AC supply on at zero volts.


My attempts were to arrange the drive signal to MITIGATE inrush
current.

** ********.


If you always turn off the current at the current zero crossing with
a positive voltage slope, then always turn on the next weld pulse
at zero voltage on the positive voltage slope, doesn't that leave
you in a remanence position to avoid saturation at the next turn on?

** Nope.

Read the link.


To turn it on it's far easier to sense the zero crossing of the line
voltage than the peak.

** Then allow a 4mS delay before firing the triac.


Under the control conditions described above where we control both
ends of the waveform to manage remanence and have a very low value
resistive load, how much would I gain by waiting for the peak line
voltage at turn on?

** Try it and see.

Most of the transformers I see are under heavy load at switch on, charging hefty filter caps. Only makes the combined switch on surge worse, compared to no load.



..... Phil