... hermetic glass-metal seal selectable. 2) Disc type phase control thyristor or silicon control rectifier (SCR), 5A ~ 5000A, 100V ~ 5000V, hermetic ... metal case with ceramic insulator. 3) Rotary type phase control thyristor or silicon control rectifier (SCR), 300A ~ 500A, 600V ~ 2000V. Features ... DC motor controls Controlled DC power supplies AC switch and thermal control Synchronous motor excitation.