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I have no experience with this but I understand you can either connect Axperts 5kVA in parallel where the output is in sync or each unit can be one phase of a 3 phase installation. It has different configurations in the software for the 2 options.

 

I don't know exactly how the bridging works and what the configuration options are, but If that is the case, then jaco_n's problems are solved!  :)

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THanks all

Superdiy . Primary I am looking for something that I can plug in the eskom 3phase as well as the solar singlephase and then on the other side only 1phase out to my main DB into a 63A mains breaker to feed ALL the circuits.  I would primarly want to run off solar during the day and battery as backup if eskom decides to shed some power. Ideally I would like power to be drawn from solar and if solar cannot  provide enough, pull from eskom. If there are more power generated from the solar and not cunsumed and batteries are fully cahrge, then feedback to grid. All to be automatic. Basically how a Hybrid works, but without the need to pay R70 000 plus for a 3 phase inverter or to have multiple inverters.

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THanks all

Superdiy . Primary I am looking for something that I can plug in the eskom 3phase as well as the solar singlephase and then on the other side only 1phase out to my main DB into a 63A mains breaker to feed ALL the circuits.  I would primarly want to run off solar during the day and battery as backup if eskom decides to shed some power. Ideally I would like power to be drawn from solar and if solar cannot  provide enough, pull from eskom. If there are more power generated from the solar and not cunsumed and batteries are fully cahrge, then feedback to grid. All to be automatic. Basically how a Hybrid works, but without the need to pay R70 000 plus for a 3 phase inverter or to have multiple inverters.

 

Hi jaco_n

 

The solution with the change over switch/contactor will not work.

 

If you want to be able to supply the load from solar and draw from ESKOM if solar is not sufficient then you'll have to have an inverter capable of combining ESKOM and solar and even more, if you want to feed back to the grid you need an inverter with grid-tie capability as well. Your only solution then would be something like the 10KW 3 phase infini going for about R45000 or maybe another more expensive 3 phase inverter with grid-tie capability.

 

If you however are willing to have your connection converted to single phase, you can look at a single phase inverter, but there you are basically still limited to the 3KW infini which have the grid-tie option and which will also still supply your load when the grid fails (load-shedding). Most grid-tie inverters cannot supply the load when the grid fails - they simply switch off and that is why I say you are pretty much limited to the 3KW infini or may something like the more expensive Imeon inverter.

 

As far as I'm concerned there is no easy (cheap) way out, if you want to keep your existing 3 phase connection and quite high load (40A? per phase).

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No the Axpert does not grid tie. So you cannot export to grid nor can you use Eskom to top up. If the load is more than the inverter can supply from solar and batteries the entire load is fed from grid. A drawback to the Axpert but a compromise I am willing to make since the Axpert is relatively cheap compared to other options. You could look at the Imeon 9/12 which is a 3 phase inverter but it is about R70 000 on its own. You invariably make some compromises with solar because of availability of components or budget. With you drawing 40A per phase and you looking to go solar, the first thing would be to reduce you consumption - LED lights, solar geyser, efficient fridge and deep freeze. Then identify what is essential for 1-4 hours load shedding and supply those essential devices, probably off a single phase inverter. As your system grows so you can add. If you want 3x 40A you are going to need a sizeable wad of cash.

 

There is a old saying "how do you make a small fortune farming? - Start with a large one!" I cannot see that you are going to get away with anything under R140 - R160K for a 3 phase system that is going to come close to satisfying your current needs and then it still may fall short of the mark. 

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  • 3 years later...

So just checking "for a friend" here - can you not do 3 x single phase inverters on a 3 phase system then?

I ask because I've seen that done a lot of times, and that has lead us to have disputes about what the ACTUAL feedback is:

Worked example:

Red Phase - importing 1kW
White Phase - importing 2kW
Blue Phase - exporting 1.5kW
For 1 hour...

I have an Itron prepaid meter and a solar logger that shows me that the above system IMPORTED 1.5kWh , exported 0.
But I have another meter that shows me the system IMPORTED 3kWh AND EXPORTED 1.5kWh

Which is right and which have you guys seen more of?

This link explains it pretty well (do you add up the phases or not before calculating import/export) - apologies that it is an Aussie link - we're talking South Africa here :)

https://reneweconomy.com.au/3-phase-trickery-utilities-ripping-off-solar-households-17282/

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16 hours ago, richjdavies said:

 

I have an Itron prepaid meter and a solar logger that shows me that the above system IMPORTED 1.5kWh , exported 0.
But I have another meter that shows me the system IMPORTED 3kWh AND EXPORTED 1.5kWh

Which is right and which have you guys seen more of?

 

I would say it is the same...

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11 hours ago, richjdavies said:

Which is right and which have you guys seen more of?

Interesting question. I actually had a case with two different modbus meters that had precisely this difference. The Carlo Gavazzi EM24 meter has energy counters for each phase as well as a counter for the total (so 4 counters in all). The ET340 has the same layout, but the way it adds it up is different.

In your example above,

11 hours ago, richjdavies said:

Red Phase - importing 1kW
White Phase - importing 2kW
Blue Phase - exporting 1.5kW
For 1 hour... 

The EM24 will report (the one I prefer):

L1: Imported 1KWh, Exported 0KWh.
L2: Imported 2KWh, Exported 0KWh
L3: Imported 0KWh, Exported 1.5KWh.
Total: Imported 1.5KWH, Exported 0KWh

The ET340 will report:

L1: Imported 1KWh, Exported 0KWh.
L2: Imported 2KWh, Exported 0KWh
L3: Imported 0KWh, Exported 1.5KWh.
Total: Imported 3KWH, Exported 1.5KWh

Why do I prefer the EM24? Well, that gives you more information. It tells you that integrated over the whole the total was zero. If I wanted the other information, I can always add up the phase information myself. With the ET340, the total is meaningless (I can already work that out for myself from the phase values), and it loses important information (the actual total). Since many countries bill for the sum over all three... losing this information is actually a big deal.

Edit: Let me add more reasoning here. My issue with the second kind of report is that you lose time information. You cannot distinguish whether the import and export happened concurrently (on different phases). It could have been that the customer consecutively imported 3KWH for one hour,  Then switched everything off and exported 1.5KWH for another hour. And there would be no way to know.

This is important, because our feed-in tariff (FIT) is usually less than what you pay per unit. In the concurrent case, you will pay nothing. In the consecutive case you will pay 1.5KWH times whatever the difference in tariffs are. For anything in between, you can't tell because the meter lost the information.

Edited by plonkster
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2 minutes ago, Javi Martínez said:

I think the procedure is the same and the only difference is in the way they show those "Acumulated Data"...

Math time! 🙂

So the way you work out energy, is you integrate power over time (since a watt is a joule per second... so integration removes the "per second" bit and you get back energy). So you do ∫Pdt for each phase to get the total energy.

So the question is whether you should, for calculating the total, do this (assuming P1, P2 and P3 are functions represent the power on the relevant phases):

∫Pdt + ∫P2dt + ∫P3dt

Or whether you should do this:

∫(P1+P2+P3)dt

I vote for the second one 🙂

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7 minutes ago, Javi Martínez said:

If it is time for math ∫Pdt + ∫P2dt + ∫P3dt = ∫(P1+P2+P3)dt

😉

Normally yes, but in these meters positive and negative values are tracked in separate registers (again, because the FIT is usually lower). I should have said that upfront, it is an important part of the puzzle. The instantaneous total power determines to which side the value is added. With the ET340 approach... the value essentially gets added to both sides, making the totals useless.

 

Edited by plonkster
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I thought I read somewhere that Victron has an inverter setting that allows you to choose between exporting power on a per phase basis or on a nett of all 3 phases.

Although certain CG meter models only report the nett of 3 phases, so that means the choice of exporting power on a per phase basis is forfeited.

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2 hours ago, phil.g00 said:

I thought I read somewhere that Victron has an inverter setting that allows you to choose between exporting power on a per phase basis or on a nett of all 3 phases.

The setting is called Phase Compensation. There is a long-standing issue for coming up with a better name for this feature. It also has some limitations that I won't bore you with (it is NOT going to balance your phases for you!), but in general it does its adjustments so as to reach zero across all three phases. What it does mostly... is to avoid feeding power through the DC bus, for example, it tries to avoid a situation where one phase is importing power while another is exporting. It will then move power over until all of them is doing the same thing (or is idle).

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6 hours ago, plonkster said:

The setting is called Phase Compensation. There is a long-standing issue for coming up with a better name for this feature. It also has some limitations that I won't bore you with (it is NOT going to balance your phases for you!), but in general it does its adjustments so as to reach zero across all three phases. What it does mostly... is to avoid feeding power through the DC bus, for example, it tries to avoid a situation where one phase is importing power while another is exporting. It will then move power over until all of them is doing the same thing (or is idle).

Then, if we have 3 Multiplus in a triphase system, can we use a monophase generator to charge batteries? @plonkster

Edited by Javi Martínez
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24 minutes ago, Javi Martínez said:

Then, if we have 3 Multiplus in a triphase system, can we use a monophase generator to charge batteries?

Yup. The Setting I speak of above is related to ESS, which is the grid-parallel feature. When running off-grid with a generator, then one Multi can charge while the others are discharging to make their respective phases.

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  • 2 years later...

Can anyone please advise if a 3phase inverter shares the power between phases and if this happens dynamically. In essence, could a 10Kw 3 phase inverter supply 4KW on one phase, 5Kw on another and 1Kw on the last phase (assuming a simultaneous draw), and then later supply 2, 5 and 3?

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  • 3 weeks later...
On 2015/06/22 at 7:46 PM, jaco_n said:

I was hoping I could move everything to one phase. but do not think 40amp would be enough.

Start at the beginning, do a power audit of all the items you want to run on the inverter to get an accurate handle on exactly what the load is. You might be surprised and it's less than 40Amps in which case you've got cheap options. If it's more than 40 Amps I'd strongly suggest you make some sacrifices to bring it under otherwise you're in for an expensive and complex installation.

 

I wouldn't consider getting council to give you a larger single phase supply as a good option, often with the old 40A 3-phase supplies they'll only have a 6mmx4-core cable for the incomer in which case they'll whack you for the cost of a new 16mm x 2-core cable as well as another few grand for a new energy dispenser plus your new supply will only be effectively half the size of your existing one.

 

**edit** Oops...just saw the date the Jaco_n posted this.

Edited by Marv
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