Very impressive feedback for sure.
I like what you have said and all application note said the same. I am living in a country where people don't want to care about theories and limitations. May be BTA 100 saves money because, 2 back to back SCR for single phase takes more space on PCB.
Group leader said me make a SSR without phase control or zerocrossing detection. I suggest MCU application to make things more accurate, but he doesn't want.
Last 2 leg circuit is reasonable, just consider a AC power source ( 380V, 40A or 440V,40A), then a SSR( what I am developing ) then a circuit breaker, a TR after then delta -Y or Y- delta R-C load.
For R-C current leads the voltage pf goes below zero, even its not purely resistive but he wants to test!
As you said dv/dt raises at a level that SCR/thyristor could not "OFF". So people use RC snubber to suppress high dv/dt. May be it woks with transients, having a dampling frequency for LC what AN-4003 explained well.
In my case if its R-L load then snubber R=872 ohm and C= 320uF. The capacitor charging time is 279mili second.
The parasitic capacitance/intrinsic capacitance plays a role for OFF dv/dt. Normally CAP of snubber should be 10 times of parasitic.
Without snubber BTA100's dv/dt is 10V/us.
When its gate is open,(may be at zero current/ holding time)its 500V/us.
Whats your in mind for safer commutation? What cause damage for R-C load now?