Concern re 3 Phase imbalance

[DIYPete]

Yes for MVHR and ftc = the Ecodan FTC5 Unit which includes the H/W tank.
Pete

 

[DIYPete]

Whoops, sorry did not notice earlier posts. Responses:

Yes, well aware of need for caution (in a previous life attended related fatalities). Aware inverter will hold charge (capacitors?).
Investigation only by me, as per previous posting I have no practical knowledge of 3 phase systems. Previous amendment (RCBO to MCB) was following discussion with qualified friend.Hoping to glean sufficient inf. to recall sparks if indeed we have a problem (yes?).
Tesla - Yes we are using the Self-powered mode with a 10% reserve on L1. Works fine (we do get a number of cuts in this area). Was not aware that it is simply a single phase unit though.
Re check on phases in use following power cut - Presumably I can cut all power on a sunny day and put multimeter across L1,2 and 3 plus common neutral to check incoming from the inverter?
Think that covers quereies raised.

Much appreciated
Pete

 

[marconi]

My 'starter for ten' drawing of your installation. Only L1 is using self-powered mode of PW2 and backed-up as you only have one PW2 and it is connected to L1. Solax is actually three inverters (I1, I2 and I3) synchronised and timed to produce a three phase output. If Solax has a maximum power output of say 9kW then each inverter is 3kW. Also, only Inverter 1 can charge the PW2. So excess power(ie inverter generation - load for that phase) generated by Inverter 2 or Inverter 3 will be exported - not stored in PW2. You would need a second and third PW2 to store excess power from I2 and I3.

Happy to discuss further later. A bit rushed right now.

 

[marconi]

Re #17: Re check on phases in use following power cut - Presumably I can cut all power on a sunny day and put multimeter across L1,2 and 3 plus common neutral to check incoming from the inverter?

Yes. I expect you will only have L1-N energised or none of the phase-N pairs energised. It depends on how the inverter's anti-islanding works.

If I had designed the '3 phases + N from one box' Solax then the loss of only one grid/supply phase would disconnect the Solax (ie all three inverters) from the grid. I will ask the inverter supplier I use for some advice on what happens.

One grid-tied inverter anti-islanding technique is to set up the frequency of the inverter to drift away from 50 (or 60Hz) or undulate around it . However, when the grid/supply is present the inverter frequency generator can detect and lock itself to the grid/supply rock -steady 50/60Hz waveform. While lock is maintained the grid supply is present; when the supply suffers an outage lock is lost, the frequency drifts and once it crosses a threshold (say 50 +/- 3 Hz) the inverter is shut down. Voltage is not a reliable indicator of loss of supply since the grid-tied inverter itself produces an emf and is connected to the supply. The Solax X3 uses the frequency drift scheme.

 

[DIYPete]

Interesting - it had not occurred to me that generated power from 2 phases are grid-bound when usage is minimal. Would not justify 2nd battery though - average drawn from grid in last 8 weeks is 190kW per week with around 25kW 'returned' to grid. Awaiting Green Grant Voucher, will ensure proposed solar thermal and emersion diverter switch on L2 and L3.

Will turn off inverter tomorrow, sun expected.

Pete

 

[marconi]

Re my #19: I have contradicted myself about the use of voltage to confirm Solax power output from each of its phases. Don't use a multimeter - instead look at the Solax readings for power output for each phase (probably labelled R, S and T). Be careful only to have a few low power loads on L2 and L3 - say lighting - so that the total power for L1, L2 and L3 is less than the prevailing harvest of sunshine. L1 of course is supplemented by the PowerWall.

I think you can see now why the Solax phase power outputs are unlikely to be the same - what is output depends on the single phase loads connected to L1, L2 and L3 at the time - and for L1 only the amount of energy being stored in or output from the PowerWall -, PV power input and the amount of grid power imported/exported. Similarly for the SMET energy meter.

PS: Units.... kW = Power and kWh = Energy

 

[DIYPete]

Ah yes, I am beginning to understand..........I think. Power readings across the 3 phases are determined by the load being applied at any one time to each of the phases, hence a likely imbalance.

The web portal for the inverter does give a 'Real Time Display' of AC Power for each phase. Now that it is clear that there is no fault, as I originally thought, there is no need to test the inverter under limited-load conditions. The portal has proved correct, to date, in its readings as compared with the Tesla app so that should be a reliable source of info. Does that mean we have finally reached journey's end?

 

[marconi]

I think so but happy to help further if needed.

Enjoyed working on it - thank you.

Marconi

 

[DIYPete]

I think so but happy to help further if needed.

Enjoyed working on it - thank you.

Marconi

In which case, thank you for your assistance ........and patience.

Regards
Pete

 

[marconi]

DIYPete: The supplier I use does not deal with SOLAX products nor know anything about their functional niceties such as if only one, just two or all three supply phases suffer a power cut. Nor what would happen if one phase is maintained by a Power Wall.

Sometime, if you have a power cut and the energy of the sun is being harvested, you could check the power outputs of the 3 inverters in the SOLAX.

I suspect that during a power cut even if the sun is shining L1 is only energised by the Powerwall.

I'd be interested to know what happens.

 

[DIYPete]

Marconi

Have not forgotten your request to check inverter in outage situation. Friend standing by on our web portal when we power down but page refreshing times are somewhat slow and, although the graph showing incoming PV dips to '0' power across the phases does not change.

Will try again (friend now going out) next sunny day and let you know.

Pete

 

[DIYPete]

Marconi
Ref. Solax X3 Inverter - state of phases with power cut.
As requested have now tried cutting power to our inverter. A friend was logged in to our web portal at the time the power was cut. All 3 phases went down and there was no power being produced.

The web portal simply recorded - 'No information available' against 'Real Time Display' with no incoming PV showing on the graphic display.

I checked the display on the inverter and a similar story there (see att.).

Hope that helps, let me know if the inf. provided is incomplete.
Once again, thany you for your assistance.
Pete