Out of curiosity, I wanted to find out if a higher current SCR will be reliable to drive the contactor coil. So, I connected three BT169s in parallel and re-tested. They survived several on-off cycles. From previous tests showing 308 mSec total delay, the contactor mechanical delay is calculated to be 170 mSec. and the single SCR time delay is 138 mSec. This test shows a total delay of 356 mSec. because now the gate RC network has to drive three SCR gates. The 3-SCR time delay becomes longer (356 - 170 = 186 mSec). This will be the end of my tests for using the mechanical contactor.
