1. Put a snubber across your load because you do not know what the Dv/Dt is.
2. If the gate drive circuit has a high impedance source, the Dv/Dt can be coupled through to the gate via internal capacitance and destroy it.
3. Ignore the failed device, the failure mode is not on the spec sheet and so its source can not be guaranteed.
Frank
The capacitor in parallel with the Triac/coil is not damped (it doesn't have a series resistor)
Therefore you have a large-Q tank circuit, which will oscillate wildly at turnoff. This could exceed the internal clamp ratings.
I know that the datasheet indicates that no external snubbing or clamping is necessary. But desperate problems require desperate solutions. Add the resistor to the snubber, and see if it helps.
What quadrants are you triggering the triac? It is not specified at the IV quadrant.
I am using a posive gate pulse. So it would work in 3+ and 1+ quadrant.
Is there any way to find the dv/dt of an load.
I am using a inductive load. But the when triac fails the terminals are shorted inside. What could be the reason for the triac internal short. I have searched in net every where it was mentioned that it would be due to high di/dt.
Do we have to consider on di/dt for inductive load or is there any other reason for the internal short.
If you are applying a positive gate pulse, then you are operating in the I and IV quadrants. See the attached image.
On this device, triggering on the IV quadrant is not specified.