When I had tested the attached circuit initially the TRIAC BTA12 damaged in surge pulse (IEC61000-4 - @2KV pulse) as well High voltage test aroung 300V AC 50Hz.
10A Slow blow fuse blown (little fuse 215 series) but it is not protecting the TRIAC.
I suspected it could be the A2s of TRIAC making it failure and selected higher A2s TRIACs for safer BTA16,20,24,41. But all got damaged.
Later suspected di/dt could be an issue and added 3.6mH in series to TRIAC BTA24/BTA41. Now it is getting passed upto 4KV surge and the current waveform limited to 1 cycle. But when higher voltage applied beyond the SMAJ350 (it comes to 295V AC RMS fusing) still TRIAC getting damaged and MT1-MT2 short noticed and MT2 -Gate is 60 ohms.
When there is no inductor there is continuous current noticed on multiple cycles and fuse blown and TRIAC also damaged.
Now I need a support to overcome the TRIAC damage for overvoltage protection
