Could be a single package snubber - usually a series CR network.No, its not a diac. It is placed in parallell with anode and cathode of SCR. It is has a case similar to DO-5 (big one).
Its always worth giving the datasheet more than a cursory glance - most thyristors are reverse blocking, a few aren't!Yeah that's my guess too. It's common enough practice to put a rectifier diode in reverse parallel across and SCR.
When the SCR is off the device supplies half wave (half power) and when the SCR is on it runs at full power. Commonly was used for things like dual temperature settings on a heater element.
by Aaron Carman
by Jake Hertz
by Jake Hertz
by Duane Benson