using tria to switch ac 220 volt

using Triac to switch ac 220 volt

what is the difference between Maximum Gate Trigger Current and Surge Current Rating ? how to know current gate that will hold?
also what is the difference between "Triac logic level" and Sensitive Gate Triac" ? which of them suits to switch as heater or ac valve?
i attached the circuit , i want your comments. i postulated that the load resistance is 50 ohm

Re: using Triac to switch ac 220 volt

mshh said:

what is the difference between Maximum Gate Trigger Current and Surge Current Rating ?

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These are the damage levels for peak input and output current levels.

how to know current gate that will hold?

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THat's called (LOAD) Holding current , IH which has a NTC coefficient and is quadrant sensitive. After zero current crossing or below Holding current, Gate trigger current pulse is needed to latch again.

also what is the difference between "Triac logic level" and Sensitive Gate Triac" ? which of them suits to switch as heater or ac valve?

Click to expand...

None
Both can be direct drive low power circuits from logic with a spec usually << 10mA and all triacs have a V_threshold of two PN junction drop with tolerance for current so current limiting R is used with 2 diode drop rule for OHm's Law. Since transistor current gain is limited, as load increases trigger level ought to be proportional to load surge expected for fast turn on such as 2.5% of output surge expected.

So it is not cold load resistance but trigger current / cold load current >2.5% to 10% max. read spec examples, tables and graphs for each part to compare. But this is generally true.
Using <<1% may be possible but use worst case specs for guaranteed results.

Thus you need to consider currents and intermediate stages from logic to high current surge loads. dv/dt snubber filtering is needed to suppress false triggers for some that are not "snubberless" and Zero-crossing switch sync for trigger gives lowest EMI problems.

what about the circuit ? you didn't comment?

Re: using Triac to switch ac 220 volt

I dont think your circuit will works........
Did you get the result in the hardware?

when U2 is on will there be enough current through U1 and R1 to keep it on?
frank