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3Phase inverter that can push all current to a single phase, if necessary?


SilverNodashi
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Hi,

Does anyone know of a 3phase inverter, which can push more current onto one of the 3 phases (i.e. for the 220V appliances one of the phases) if necessary?

Let me explain: on an Inifini 10Kw 3phase inverter, each phase can essentially draw upto (theoretical, I haven't tested this exact figure) 3.33Kw per phase. The problem is that although the inverter is 10Kw, one will never be able to draw say 4Kw on a single phase - for example a big compressor, induction motor, etc. Going 3phase does solve that problem but only for 3 phase appliances.

So the question is, is there an inverter which can divert unused power from one of the other phases to the heavily loaded phase, if / when necessary?

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I doubt it, if you require e.g. 5Kw on one phase you will have to get a 15Kw inverter.

See, the problem I have with that is that one spends about R20k more for say a 15K inverter, just to have the extra 2Kw on a phase ffrom time to time. Ideally the inverter should be able to allocate power to the phases as necessary, the same as some inverters know how to optimally utilize one or more MPPT trackers + battery + grid feed.

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No, balance the loads correctly.

If you have 3 phase, why not use it correctly and install a 3ph motor on the 1ph equipment.

I can't balance the loads correctly. Even with the loads fully balanced, a 4KW heating element trips the inverter! It's a 22V single phase urn. So now I'm forced to buy an expensive 3phase urn, or a 15KW 3phase inverter. The a 10Kw 3phase is running at about 20% most of the day. It's a waste of money and resources, IMO to upgrade just for this purpose!

But hopefully some clever engineer will notice this post and make an inverter that can be better utilized in cases like this.

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Ok, to each his own, but for me running a 4kw urn sounds like extreme waste.

Now you blaming an inverter for not being able to run an urn?

Who still use those anyway?

Replace the urn element with a 1kw unit?

Replace the complete urn with a 3ph quickboil water heater.

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Ok, to each his own, but for me running a 4kw urn sounds like extreme waste.

Now you blaming an inverter for not being able to run an urn?

Who still use those anyway?

Replace the urn element with a 1kw unit?

Replace the complete urn with a 3ph quickboil water heater.

ok so now we argue about what to use and what not to use on an inverter..... Guess innovation halts because of arguments like this. No worries....
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Ok, then lets stop right here :)

If your inverter is too small to power your load, do not blame the inverter or its maker, buy a bigger unit.

 

If on the other hand you trying to save money by going solar, good for you.

If you still insist on running wastefull equipment on said solar install, bad on you.

 

For the life of me, I cannot think of another piece of equipment as wastfull of energy as an urn.

 

If you still insisting on running your unbalanced load, then perhpas look at running 3 single phase inverters, say two 3kw units on 2 phases and a 5kw unit on your "urn" phase.

It will cost you less than a 5kw 3ph unit, perhaps???

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Ok, then lets stop right here :)

If your inverter is too small to power your load, do not blame the inverter or its maker, buy a bigger unit.

 

If on the other hand you trying to save money by going solar, good for you.

If you still insist on running wastefull equipment on said solar install, bad on you.

 

For the life of me, I cannot think of another piece of equipment as wastfull of energy as an urn.

 

If you still insisting on running your unbalanced load, then perhpas look at running 3 single phase inverters, say two 3kw units on 2 phases and a 5kw unit on your "urn" phase.

It will cost you less than a 5kw 3ph unit, perhaps???

You're missing the whole point here. Irrespective of what is being run on the inverter, it's more a matter of a 10KW inverter idling at 20% it's entire life simply because the house setup is 3 phase.

Buying new equipment defeats the purpose of saving money with solar. The current setup cost about R4/kw to run as it is.

For 3phase this is fine and most of the 3phase items in the workshop work fine.

The point I'm trying to get across is that it should be possible to channel current through to a single phase, if / when needed, as apposed to having it split (balanced) between the 3 phases.

This is the same as having a 1040Ah battery bank, but being told you're only allowed to use 20% of it. So for R120,000 investment you only get to enough about R20,000 return. Does that make any sense? Definitely not from a financial point of view. Nor from a "saving eskom with solar" point of view.

P.S. I am looking at replacing the Inifinisolar 10KW with 3x Axpert 5KVA's, but due to a space limitation probably won't be able todo it either.

P.S.S. Think of this thread as a possibility to make something greater than it already is.

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Perhaps have your smaller 3 phase setup and give the urn its own 4kW single phase. Then you only have 1 inverter idling. Is the urn used in an industrial application? If not maybe reduce the size of the element. I am looking at installing a geyser with  2 x 1000W elements that can "mop up excess energy". I live nearly 9km from the grid so a grid tie is not the answer. Mind you with all the tariffs to grid tie I would rather heat water. The heated water will be used in domestic applications which already have gas geysers so hopefully will reduce the gas bill. 

 

I know that solar water heaters are much more efficient  than PVs but they are limited to heating water. Having made the investment in an inverter I would at this stage rather invest further capital in more PVs which would predominantly heat more water but could power heavy machinery in the workshop or be used to charge batteries for a future electrical vehicle or anything that one chooses.

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Hi Silver, it's mainly a question of cost.

To do 5kw you need thyristors that can carry the load.

So to build a 3kw unit that can run 5kw, what's the use? You just call it a 5kw unit then.

Would you pay 5kw pricing for a 3kw unit?

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Perhaps have your smaller 3 phase setup and give the urn its own 4kW single phase. Then you only have 1 inverter idling. Is the urn used in an industrial application? If not maybe reduce the size of the element. I am looking at installing a geyser with  2 x 1000W elements that can "mop up excess energy". I live nearly 9km from the grid so a grid tie is not the answer. Mind you with all the tariffs to grid tie I would rather heat water. The heated water will be used in domestic applications which already have gas geysers so hopefully will reduce the gas bill. 

 

I know that solar water heaters are much more efficient  than PVs but they are limited to heating water. Having made the investment in an inverter I would at this stage rather invest further capital in more PVs which would predominantly heat more water but could power heavy machinery in the workshop or be used to charge batteries for a future electrical vehicle or anything that one chooses.

The urn is one example of what we have on the farm. Then there's 3x 200L geysers with 3KW elements, 4x deep freezes, 3x combi fridges, some TV's, lights, electric fences, etc.

So I'm contemplating putting in 4x Axpert MKs 5KVA - 3 in 3phase with a 4th one on the Red phase where the urn is used (having camps from time to time + hunters in season, a kettle just doesn't work. And it's too far for gas heaters. but space is really really limited close to where the batteries and solar panels are. With 36x 255W panels on the roof, I think there's more than enough PV, I just need to get a way to optimize it all, without spending another R80k or R100K!

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Hi Silver, it's mainly a question of cost.

To do 5kw you need thyristors that can carry the load.

So to build a 3kw unit that can run 5kw, what's the use? You just call it a 5kw unit then.

Would you pay 5kw pricing for a 3kw unit?

Not quite... Right now there's 3x 3.3Kw circuits in the same inverter, so it shouldn't be that difficult to divert some current (as you say with Trisistors) inside the same unit.

Let's say I have 3x 100W solar panels and I want 300W electricity. Do I toss these onto the shelve and buy a new 300W panel, or just connect them together with some solar cable and MC4's?

Or I have 4x 200Ah batteries, which could give me 800Ah if connected together. Or I can go buy a new larger battery to deliver the same power.

In theory I don't see why this can't happen. In practice, probably because most marketing managers and engineers from these brand argue like you do: "If it's too small, buy another one. Spend more money".

The fact is, on a 3phase inverter, there's surplus power that could be better utilized. This inverter already cost R40k and it's too late to return for refund. So now I have to spend another R40-60K on 4 or 5 Axperts. So let's say I just spend R100k on inverters, but can only effectively utilize 40% of that investment.

This thread isn't about finding alternative, expensive solutions for the problem, but rather to see if there's a more innovative solution to these kinds of challenges.

As another example: A very expensive solar pump system was put in and the pump only runs for about 3 hours before the storage tanks are full. The PV array is 8x 110V panels, and effectively it's wasting 50%-60% of it's potential. When asked whether it can drive another pump, 3 KM away, the simple answer was no. Another R70k investment has to be made.

When asked whether it could store excess energy in batteries, the answer again was "no".

So I get the feeling that these items are purposefully created to serve their absolute minimum requirements. Although the technology is there to harvest and utilize more energy, the technology isn't developed with that in mind. In stead we're forced to spend more money, pay more taxes (which goes back to the corrupt government who doesn't want to help eskom....). Do you see where this is going? If you could utilize say 60% of you PV power, instead of the average 28%, wouldn't you want to?

Similarly, if the inverter could be utilized better, we could all enjoy the 98% efficiency. Instead on average we utilize 30% of it. 68% is wasted investment.

For many years, system administrators forced companies to buy expensive servers, one for each task - i.e. one for the mail server, one for the web server, one for the print server, one for the file server, one for development, one for staging, etc. All those server sit and idle in the rack, 24/7. But virtualization changed that in the past, say 6-8 years. Now you can buy one single server and utilize it much better, serving all those roles from one single piece of hardware - it uses less electricity, radiates less heat, takes up less space (office real estate also cost money), need fewer admins to manage.

The question is, how long before renewable energy manufacturers see the bigger picture, and build equipment with higher overall efficiency levels?

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Another option is 2 Axpert 4Kva's on 1 phase and another 2 on the other phases.

Red phase = 8Kva

Yellow phase = 4Kva

Blue phase = 4Kva

I need 3 phase. The farm runs 3 phase, i.e. the borehole pumps, drill press, compressor, lathe, etc all run on 3phase.

We'll see how 4 Axperts go, but now we need to make some building alterations to fit 4 on the wall.

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I need 3 phase. The farm runs 3 phase, i.e. the borehole pumps, drill press, compressor, lathe, etc all run on 3phase.

We'll see how 4 Axperts go, but now we need to make some building alterations to fit 4 on the wall.

Drill  holes in the wall and mount some on the other side if it is an internal wall.

 

Your expensive pump does not seem to be geared to your needs. When it needs replacing go for a smaller one and then you can use your excess panels. I have two pumps one with 1.2kW of panels and it delivers about 2500l/h and the other has one 175W panel and delivers about 3000l/day. That 3000l is enough to supply the drinking requirements of 60 cattle. There is a large 450 000 l reservoir and so I can run more than 100 cattle there for months as long as the reservoir is full to start with. 

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Hi Silver

I'm no electrical engineer but I think one of the issues with combining the 3 phases onto one is that the phases are 120deg out of phase? I think the only way to solve that would be to convert back to DC with a rectifier and back to AC (now in phase with the target phase) with another inverter. As I said, I don't know much about this stuff but to me it seems like the phase angle could be the obstacle.

On the Axperts, not sure if you already have batteries but an 5kVA Axpert unit requires at least 200Ah @ 48V bank. They cannot operate without a battery bank. If they operate in parallel I think they can share a bank. jdp on here runs two in parallel, he'll be able to give better advice.

C

Sent from my iPad using Tapatalk

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Hi Silver

I'm no electrical engineer but I think one of the issues with combining the 3 phases onto one is that the phases are 120deg out of phase? I think the only way to solve that would be to convert back to DC with a rectifier and back to AC (now in phase with the target phase) with another inverter. As I said, I don't know much about this stuff but to me it seems like the phase angle could be the obstacle.

On the Axperts, not sure if you already have batteries but an 5kVA Axpert unit requires at least 200Ah @ 48V bank. They cannot operate without a battery bank. If they operate in parallel I think they can share a bank. jdp on here runs two in parallel, he'll be able to give better advice.

C

Sent from my iPad using Tapatalk

I'm not an electrical engineer either though I'm going todo the course next year.

There's already a 600Ah battery bank on the infinisolar inverter which I'm going to use so I'm sure it won't be a problem - hope it's not too small for 4 Axperts. I have setup a shared system like jdp's as well, it's quite easy todo.

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Hi, Does anyone know of a 3phase inverter, which can push more current onto one of the 3 phases (i.e. for the 220V appliances one of the phases) if necessary? Let me explain: on an Inifini 10Kw 3phase inverter, each phase can essentially draw upto (theoretical, I haven't tested this exact figure) 3.33Kw per phase. The problem is that although the inverter is 10Kw, one will never be able to draw say 4Kw on a single phase - for example a big compressor, induction motor, etc. Going 3phase does solve that problem but only for 3 phase appliances. So the question is, is there an inverter which can divert unused power from one of the other phases to the heavily loaded phase, if / when necessary?

Another solution but will probably cost both arms and legs.

2 phases feeding a 5000vA transformer = 380V primary - 220V secondary.

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So I skimmed this thread a little and I think there might be a fundamental misunderstanding of 3-phase here.

 

The AC on the three phases are separated by 60 degrees. Now in some ways this is analogous to a 6-cylinder engine. Mechanics know that in a straight-6 engine all secondary forces cancel out (a piston going one way is canceled out by another going the other way) which makes the engine very smooth. Now the phase separation here has the same idea, as one phase has the voltage swinging up, another is swinging down, and the third is just rounding the peak.

 

The idea is the same. Instead of building a large 3-liter single-piston engine, you build a 6-cylinder engine with 0.5 liter per cylinder.

 

Asking to build an engine that can, on demand, do more work while running on one cylinder is to miss the point of using more cylinders.

 

3-phase really is fascinating. It arrives on the premises on 3 wires. Then it goes into a star/delta transformer, so 3 wires go in, 4 comes out. The 4th wire is ground, and it connects to the center tap of the star-configuration. If you properly balance your phases, the current on the ground wire is close to zero. Overload one of the phases... and you really need an oversized ground connector... which these systems usually don't have.

 

In short, I think there is probably a reason that no inverter can do this. It's a bad idea to run a 3-phase system that badly out of balance.

 

:-)

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So I skimmed this thread a little and I think there might be a fundamental misunderstanding of 3-phase here.

 

The AC on the three phases are separated by 60 degrees. Now in some ways this is analogous to a 6-cylinder engine. Mechanics know that in a straight-6 engine all secondary forces cancel out (a piston going one way is canceled out by another going the other way) which makes the engine very smooth. Now the phase separation here has the same idea, as one phase has the voltage swinging up, another is swinging down, and the third is just rounding the peak.

 

The idea is the same. Instead of building a large 3-liter single-piston engine, you build a 6-cylinder engine with 0.5 liter per cylinder.

 

Asking to build an engine that can, on demand, do more work while running on one cylinder is to miss the point of using more cylinders.

 

3-phase really is fascinating. It arrives on the premises on 3 wires. Then it goes into a star/delta transformer, so 3 wires go in, 4 comes out. The 4th wire is ground, and it connects to the center tap of the star-configuration. If you properly balance your phases, the current on the ground wire is close to zero. Overload one of the phases... and you really need an oversized ground connector... which these systems usually don't have.

 

In short, I think there is probably a reason that no inverter can do this. It's a bad idea to run a 3-phase system that badly out of balance.

 

:-)

these are valid points, in a 3phase environment but doesn't yield true in 3 phases being used for single phase. There's no Delta or Star configuration that needs to be adhered to anymore.

The infinisolar inverter is a bloody nice piece of machinery for the price. Other 3phase inverters also work very nicely, but this one has battery backup. With others I need another piece of expensive equipment to connect to the batteries.

Anyway, so we're going to install 4x Axpert inverters in the next week or so - 3 in 3 phase + 1 extra on the red phase in the house, and then take it from there. Luckily with this setup I can still fully utilize the 9Kw solar array and battery bank.

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