Somethings's wierd.
Light and fan should have two different controls.
1. Light should work when the door is opened and when cooking.
2. When cooking fan, light and triac should turn on at the same time.
3. Triac should cycle, but I think only when percentage of time is used.
4. A thermal on the magnitron should be able to turn off the magnitron if it overheats.
5. There are two sets of interlocks for the door.
6. Set one will short the fuse if misadjusted.
7. The second set controls the light (door open: light on/magnitron off); Door closed (magnetron enabled)
There are a few Caveots for all of this.
There should be a short delay after the triac turns off before it's enabled again (1 line cycle should be OK) (continuously on is OK)
You may have to bang the triac for a full cycle of voltage. Look up triac controls of motors.
Most important is that the % on time is NOT equivalent to % heating. That has to be determined some other way. Not sure how.
The problem is that the filament of the magnetron has to heat up.
I think, you can use temperature rise to figure it out. e.g. Run a few minutes with tap water at 100% measure the rise in temp. Make sure that when you input 50%, it rises 1/2 the number of degrees and at 10%, 0.1 of the number of degrees. You have to experiment with this.
e.g. a 10% on time, might really mean that the actual time on is 15%.
Two methods can be used. One is phase angle fired and one is known as Zero Crossing Pulse. In the latter, a number of full cycles on and full cycles off are used. Phase angle firing is harder because only part of cycle is used.
Because this is an inductive load, and a triac will turn off at zero voltage and because it's inductive, the voltage and current zero crossing will not co-incide, therefore that once a voltage zerocrossing is found, the triac must be continually pulsed to just before the next zero crossing. If a current zero crossing occurs before the next voltage zero crossing, the triac will turn off.
I hope I didn't miss anything. The magnetron filament and high voltage turn on at the same time `because the filament and HV come from the same transformer.
The magnetron, HV and blower should come on at the same time. They must be interlocked.The light comes on when either the door is open or the blower is on.
The interlock consists of both primary and secondary interlocks. One will crowbar the fuse if the other interlock isn't activated. Usually these detect bent doors, so there are one at each end. If one interlock works and the other doesn;t the fuse gets crowbared. The other switch usually enables power and turns on the light. The blower will turn on the light too.