Does the triac conduct current when closed?

Question

Electronics

Good day,

I met a triac on my way. Because of which, a couple of questions, I did not find clear answers to them (information differs in all sources)

1. Does the triac conduct current in the locked state? This refers to the alternating voltage 220V 50Hz. Let's say I made a decoupling through an optocoupler. I connected a phase to one leg of the triac, - from the other leg I remove this phase.
Question: will there be some current (even if minimal) on the leg of the triac? Will an indicator screwdriver show the presence of current?

2. Can the starter completely replace the triac? If it is normally cooled and not subjected to high peak loads, then its life is not limited?

3. Why is the phrase often found on the Internet "in our networks they do not live long" (meaning home networks)

PS I don't have a triac myself, I can't check it. Actually, it depends on the answers whether I should buy it or not.

Answer 1

1. Formally, yes, it does. But this leakage current is extremely small, as in any other closed silicon PN junction. Of course, if the temperature and the limiting reverse voltage for this transition are not exceeded (if it is exceeded, then this is a breakdown, and the current is already determined by the properties of not the triac, but the rest of the electrical circuit). For a neon indicator screwdriver to glow, the leakage current is usually not enough.
2. Not only can, but has long been replacing. Its service life is indeed many times (by orders of magnitude) longer than that of a contact one, both in time (subject to operating conditions) and in the number of inclusions.
3. I do not know where this phrase can come from. We need to look at the context - maybe it explains what is meant. If this is the presence of a large number of peak excesses of the rated voltage in the network, then we would observe a massive failure of household and industrial equipment - but this is not observed. However, even if it were, then it is easy to insure against this - it is enough to take triacs for a higher operating voltage. Say, if you take a 600-volt triac for a 220-volt network, then it will never burn out.

Answer 2

1. closed no. except for leakage currents - see documentation.
the scheme is incomprehensible - figure out how it works and everything is ok.
2. if the triac works within the parameters declared by the manufacturer, then it will work for a long time. there is both continuous power and pulsed current and all that.
if the load goes beyond the declared parameters, then most likely it will quickly degrade (but under certain conditions, again, it is possible and will work).
3. obscene consumer attitude, the use of poorly assembled devices without good protection, leads to various network interference. but I haven’t come across a strong horror that will burn a properly applied triac for a long time.
you did not provide the conditions of use, the brand of the selected triac and other circuitry. so nothing concrete can be said.