Is that circuit really correct, or I'm missing something ?
I think that U2 should be in series with TR1 primary.
I liked the way you specified TR1:
Several KGs transformer.
;-)
Yes it's a dubious design, but the ZCD version is less likely to cause self triggering than the triac itself. So it's probably not the problem. But it's good practice to place the MOC behind a snubber, as in the manufacturer's circuit examples.I doubt that the moc3041 work fine in such conditions. Replace by a microrelay.
Unlikely for a "several kg transformer". More likely the capacitor is too small. I would go for a strong snubber with 0.1 to 0.22 µF X2 capacitor and a respectively lower series resistor.It could be that C3 is resonating with the primary inductance of the transformer. Try a value of .001. I have had this using a triac to switch a relay.
The Opto MOC3041 is driven by a Schneider PLC output. Datasheet only say "Positive Logic Discrete Transistor Output". Don't know the actual circuitry. Anyways, I can see the input led switching normally.What is the kind of circuit that drives the opto, open-collector, push-pull, etc ...? By the way, you are right regarding to the path of the power, for some obscure reason I was mistaken in the analysis done earlier.
Just to check: Could you confirm if the Varistor is not getting hot ?
Going for certain particular industrial Solid State Relay is difficult due to import barriers in my country that make almost impossible for the resellers to get them. Will look for something like that anyway. How do you control phase angle firing in this case?Easiest solution is just to buy a commercial solid state relay.
But it will need to have two specific features.
Be the instantaneous turn on type (not just zero crossing) and have inverse SCRs (not triac control).
These work very well phase controlling partly inductive loads, and it will also provide the optical isolation.
Something like a Crydom D2410-10 perhaps ?
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I don't think that a micro relay would work in the long run due to the frequency of the commutation: 1000ms OFF ~ 200ms ON.I doubt that the moc3041 work fine in such conditions. Replace by a microrelay.
I will install a stronger Snubber filter as suggested and let you all know.Yes it's a dubious design, but the ZCD version is less likely to cause self triggering than the triac itself. So it's probably not the problem. But it's good practice to place the MOC behind a snubber, as in the manufacturer's circuit examples.
Unlikely for a "several kg transformer". More likely the capacitor is too small. I would go for a strong snubber with 0.1 to 0.22 µF X2 capacitor and a respectively lower series resistor.
Regarding the circuit you posted, how do you control de firing angle there? R11?I’ve used this circuit to control an AC motor, which is surely a high inductive load, and worked fine with an open-collector output drive.
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Something suitable is often available from e-bay.Going for certain particular industrial Solid State Relay is difficult due to import barriers in my country that make almost impossible for the resellers to get them. Will look for something like that anyway. How do you control phase angle firing in this case?
Something suitable is often available from e-bay.
For phase control you need the instantaneous "on" type, sometimes called "random fire". This will turn on at any part of the mains cycle as soon as the PLC tells it to turn on. Turn off will always be at the next zero crossing.
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