We used BT139X-600E triac. Opto triac MOC3052 used for triac's control. Load is 230V, 50 Hz LED lamp, current is 30 mA. Current is not very nonlinear - it is short "pulses" in the maximum of voltage 230 V. The triac must withstand a short-circuit current of 100 A during 10 mS. The problem is that the triac sometimes does not turn on - the reason is most likely a very small current and a large current nonlinearity. We'd like to use BTA12-600BW. Maybe someone can tell what to do in this case?