That is EXACTLY how sense senses things. direction included.
Along your same logic: since it is AC voltage, there is no polarity as well ?
60 times per second it changes direction. I assume Sense samples at > 20Khz.
That would include polarity for both voltage, current and powerfactor.
Sorry to hear you have made a conclusion without knowing the technical details.
OK - simple question
Sense can see the phase relationships (all are in phase in this example). Sense can also see phase angle changes (power factor changes). And I’m guessing that Sense connects small changes in voltage and phase with big transitions in current / power that occur on a single CT, to do the initial mains matchup. But there is no obvious direction with AC as there is with DC.
Inside the sense unit the signal of the CT (current) Is converted to voltage by simply connecting it to a resistor. Then an AD converter reads the voltage.
Sense is already on and knows the polarity of the grid.
When pv comes back on , if the voltage over resistor drops while main is going up software will interprate as out of phase and will software wise invert polarity.
I understand the shunt resistor ADC part. The challenge is that even though Sense presumably knows orientation of mains CT (flipped or us flipped) and phase assignment (V0 has been matched with C0, and V1 has been matched with C1), Sense still has no way of knowing from the result you mention whether everything is lined up perfectly (both unflipped, and phases correct in the physical layout) or whether phases are swapped on the solar and both CTs are flipped. Both of those configurations would give the same result, with both AC currents matching voltage polarity. Plus there are three other possible outcomes - both not matching the voltage ( both flipped, but phase correct or no flips and phase crossed), and both combinations of one matching and the other not ( phase correct and one flipped, or phase crossed, and one flipped).
Now if only one leg on the inverter turned off at a time, that would resolve, but I don’t think that happens with inverter shutoff.
Arggh you are driving me mad.
solar inverters are 240 volt, it does not have individual legs. it is both or nothing.
You make a statement, i say you are incorrect and now you fight me to prove you wrong ?!
Since you as a volunteer moderator have short leads to Sense, ask james to explain it to you.
Since you are obviously not believing my word(s)
I will stop now. i have better things to do.
@dannyterhaar , that’s my point. It is all or nothing with the inverter, with both legs energized or neither - that’s why your suggested approach can’t work - there’s no way to tell between the two scenarios I describe, even if both currents match voltages.
But you are also wrong - single split-phase inverters deliver two 120V phases to your house - neutral wire is typically required (my SolarEdge has a neutral connection) and even if it isn’t there, the grid will “enforce” a neutral. That’s why you need two CTs on the solar grid ties or breaker feed-ins, instead of one. Not trying to prove you wrong - just trying to explain AC voltage, current and power relationships in a single split-phases system. Not as simple as Sense makes it seem.
I’ll talk to James. Thanks.
Has anyone called you stubborn before ?
This is electric diagram of an Enphase setup I recently installed.
The neutral goes to the combiner box, but the 2 wires that go the micro inverters have no neutral.
From the manual of enphase combiner unit
In this example there are 3 strings with IQ micro controllers and one of the 240 volt wires is lead through the single CT.
So why is Sense using 2 and Enphase only 1 ?
@dannyterhaar - that’s good question. I’m not sure why two CTs are used. Inverters are essentially force-balanced, delivering equal current/energy between the two phases, so monitoring only one is probably sufficient. My Sense solar production from L0 and L1 (essentially SC0 and SC1 currents)
are never more than a few watts different from one another. But as I mentioned, my older inverter definitely has a neutral connection.
I am 100% certain sense probes both ct, can see the polarity of the amps. so after restart of the inverter if one reads negative they could solve that in software by negating the answer.
Curious what James has to say.
