ThanksJust looking at the datasheet for the T410 shows that it could require up to 10mA gate current to turn it on. Your 150 K series resistor will only give about 2 mA at the crest of the waveform (About 308 volts.)
For the photo transistor in the TLP521 to not provide any gate current is must be able to stand at least 308 volts between the collector and emitter. It is only rated at 55 volts.
ThanksYou seem to have picked devices at random without checking that their specifications meet the requirements of your circuit and without doing any calculations.
I read the T410 and many other datasheets. I noticed that in some cases the "Maximum Rank" tables show the worst cases rather than continuous operating parameters (like I(gt)-4A for 20 uS). But usually other tables have three columns called "Min", "Typ" and "Max" which show parameters related to continuous work.you need to read the datasheet.
Table 1 at the very begin of the document shows range that Igt is 5-35mA for the product range (more than one product described)
Table 3 shows that absolute maximum gate current is 4A (max 20us)
Table 4 shows actual test conditions with Igt value of 10mA for T410. That is the recommended value for gate current for T410 as tests are used to prove that something works normally. if you want more sensitive device, choose T405 which can do the same thing with 5mA gate current.
Thanks for your great tip(Turning on traics and SCRs slowly makes them susceptible to damage.).Turning on traics and SCRs slowly makes them susceptible to damage. You want a sharp transition from 0 V on the gate to more than the required trigger current. Triggering on the slope of a sine wave can work but is not a good idea. Notice that most lamp dimmer circuit you find on the internet (as below) use a daic to make a trigger pulse for the gate by dumping the charge in the timing capacitor (C1) into the gate with a very low rise time.
View attachment 274028
The MOC3043 uses an internal triac to dump a fasts risetime pulse into the gate. Not only that, but it has circuitry to make that the gate is only driven when the power line is near a zero crossing, thus reducing the stress on the triac and at times other circuitry compared to the case in which the traic can be switched on when the line voltage is high.
You can check it again.IGT or I(gt) is an indication of the sensitivity of the triac's gate threshold current. IGT (Max) would then be the maximum threshold voltage for the conditions specified, meaning that the actual threshold will not be higher than that.
I could not locate your attached document.
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