The SKT 551/18E from Semikron Danfoss is a Silicon Controlled Rectifier with Breakover Voltage 1800 V, Breakover Current 8000 to 9000 A, Gate Trigger Voltage 3 V, Gate Trigger Current 250 mA, Temperature Operating Range -40 to 125 Degree C. Tags: Disc. More details for SKT 551/18E can be seen below.