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| Problems with triac switching a toroidal tranformer |
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| Benta:
As we don't know your circuit, there's not a lot we can say. But the target is to fire the Triac at UMAX, take it from there. |
| rstofer:
--- Quote from: SebiTNT on January 08, 2019, 05:49:52 pm ---Everyone can use my pictures under the CC BY-NC license. So you are of course free to use them. Thanks for asking! Thank you all for your answers! So I think there is some inconsistent fault in my circuit. I will investigate this. --- End quote --- It's the residual magnetic flux, not the circuit. Well, except for the part where the transformer isn't firing at a particularly advantageous point in the voltage waveform. |
| BravoV:
--- Quote from: SebiTNT on January 08, 2019, 05:49:52 pm ---So I think there is some inconsistent fault in my circuit. I will investigate this. --- End quote --- Don't think its a fault, as that is normal for inductive load, like transformer, motor, vacuum cleaner and etc. I know it sounds funny, its matter of luck, whether you switched on at the moment the mains line was at peak AC voltage, or at near zero, that will make huge difference, its like tossing a coin, literally. Watch my thread as pointed by not1xor1 above, soon I will update my little project there, with details measurements (voltage and current) with/without softstarter, and also what happened when I switched a inductance load at peak or zero voltage, hell, this is also matter of luck if my scope can single shot capture at the right exact moment as yours, thru switching on and off like crazy perhaps. :-DD Suggesting to read this -> Beware of Zero-Crossover Switching of Transformers Your scope shots below is very similar to Figure 4.A at above document. |
| Benta:
I hereby retract all my previous comments! A closer study of the AC current traces provided do NOT look like saturation. It looks much more like an asymmetric current draw on the secondary of the transformer. What exactly it is, is unknown at this time, and why it's intermittent is also a mystery. More info is needed. |
| rstofer:
The triac will turn off at current zero crossing which will be very close to the maximum voltage. For 60 Hz, I would turn the triac on at voltage zero crossing + 16 ms but to turn it off, I would probably do that at voltage zero crossing knowing the triac would turn off a few ms later at current zero crossing. As to scoping the signals, if I were doing this digitally, I could bring out any trigger I wanted including zero crossing. |
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