Chris, I believe I understand your explanation I picture the diagram perfectly in my head no need for it and it makes perfect sense now. Let me give that a go. I am running at 60hz so my half cycle time period would be 8.33mS
So for half power I would turn on 4.16mS after zero crossing, 25% 6.25mS after zero crossing and 10% would be 7.49mS after zero crossing. Sound about right?
Regards
David