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3 phase options


jaco_n
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Not sure if this is the fcorrect thread to place it,but hope someone can help me

 

I have 3-phase at home. I bought the house as is. Looking at the options available, it is almost double the price as single phase . Is there such a device / conversion I can implement that I either connect all three phases and convert it to a single phase, from there into an inverter / UPS with additional solar panel power. From there feed a single phase into the main DB as per normal installation? I do not have any equipment that is wired for 3 phase, just everything is split over the 3 phases

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See this link:

http://www.sinetech.co.za/ups.htm

Look under "DOUBLE CONVERSION ONLINE UPS SYSTEMS THREE PHASE INPUT / SINGLE PHASE OUTPUT"

I don't know of any hybrid inverters that can have single phase outputs and three phase inputs.

Using a double conversion 3 in 1 out ups you could balance your 3 phases perfectly and be as low as possible on the R/kWh sliding scale.

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Hi Jaco_n,

 

A 3 phase to 3 phase Solar invertor I have not yet seen under 70KVA.

You can use 3 single phase invertors to create a 3 phase system, but why?

You stated you have NO 3 phase equipment.

 

You can still get away with only 1 single phase invertor!!!

Move all the loads you looking to backup onto a single phase. All other loads can be split between the remaining 2 phases.

Now you just backup that single phase :)

 

Not sure which area you located in, but here in CPT 3 phase connections costs way more than single phase.

You could ask your local supplier if there is diffrent monthly charges for single phase.

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Jaco I would convert everything to single Phase ,the only reason people use three phase is if they have 3 phase appliances like Boreholes.

And even if I had a borehole I would not bother with 3 phase.

 

As Wetkit said it is easy to covert the system.

 

You can also ask the municipality to change the meters. 

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Thanks all for the reply. The issue is that it is 3 x 40amp breakers and ideally I would like to put everything on. I only need about backup power for 1Kw constant for 2 hours but the idea is to roll out solar and or wind.

 

Wetkit, I actually do live in CPT and pay the same as single phase. R1.34 per kwh under 600kwh and R1.60 (something) over 600kwh. I do not really want to ask the municipality to change the meter as it will cost me more than R4000 for them to come out and do it. Plus it is one of the very old spindle meters. Will look into the UPS option and see how it can be integrated with solar.

 

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

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Thanks all for the reply. The issue is that it is 3 x 40amp breakers and ideally I would like to put everything on. I only need about backup power for 1Kw constant for 2 hours but the idea is to roll out solar and or wind.

 

Wetkit, I actually do live in CPT and pay the same as single phase. R1.34 per kwh under 600kwh and R1.60 (something) over 600kwh. I do not really want to ask the municipality to change the meter as it will cost me more than R4000 for them to come out and do it. Plus it is one of the very old spindle meters. Will look into the UPS option and see how it can be integrated with solar.

 

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

just leave your stove on L1 and your geyser on L2 and use L3  for all plugs and lights, go and buy a single phase inverter and off you go, even like that if you have the old rotary meter....it will reverse back with your surplus energy.

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Thanks Mike, but trying to get everything on it...:-) Then main aim would be to run of solar / wind during day time thus shifting geyser on time etc to peak production. The battery will only be used if there is loadshedding an dduring that time the gesyer and oven should not be used.

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okay, then you have two options for 3phase units, the infinisolar 10kw - i have installed a few, works just as wells as the single phase unit and then the new Imeon 9.12 unit, available from month end but pricey...

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Hi DeepBass9. Thanks for the feedback. Can you possibly post a pic of what he did? Interested to see what AMP breakers you have on the phases as mine are 3 x 40 amp. If I swaitch on everyting, then 1x 40amp feed  wont make it.

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This is what the electrician did to bridge the phases. Neutral is common to all phases so it was just a matter of taking the single phase feed from the inverter and bridging the three phases so they work as one. Note that there is no 3 phase equipment in use!

 

10cm of wire is much cheaper than a 3 phase inverter..

 

3p.jpg

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Hey Jaco, just for clarification purposes you cannot do what DeepBass9 did with the utility 3 phase supply connected. You will cause a Phase-Phase-Phase (3 Ph) short circuit. Resulting in huge currents and a lot of sparks.

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That is why I asked if DB9 is completely off-grid. This setup cannot work otherwise.

 

3 phase gives 380 Volt between phases and 220 Volt from phase to neutral. That is why the inverter can be connected in this way as long as there is no 3 phase equipment connected and no 3 phase grid connection.

 

With this setup you will still get 220 Volt from phase to neutral but your phase to phase voltage will now be 0 Volt.

 

If Jaco_n wants to still feed his inverter with the grid, he can disconnect 2 phases and just feed his inverter with one phase and neutral, and with DB9's setup feed the house. 

 

The problem will then be that the 3 phases from the grid will be unbalanced as you will only draw current on one phase. This should be fine up to 5Kw.

 

The best is to get an open Delta transformer to convert 3 phase to single phase if you still want to be connected to the grid or get three small inverters.

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You can split-off one of the phases and run it through a single phase inverter. Then make sure all the essential items are on that phase and keep the stove / geyser / etc on the other two phases. Just make sure you split the neutrals for those lights / plugs off onto it's own neutral bar as well. 

 

Or, use 3x Axpert 5KVA or 3x Microcare 5KW units and set them up in 3phase configuration. 

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Hi Jaco, the switchover panel you are suggesting looks good and am sure that they available. As you mentioned you would just need to check that the SANS code requirements are met.

 

Bit confused as to how you are integrating the battery charger into the setup. Could you please expand on that?

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Hi Carl, thanks for the feedback. It's something that I was wondering on if it is possible to do. Hence I draw the diagram to explain my thinking. Whether the flow of things are in the correct order, I do not know and would like to get some assitance from people that know more than I do. I am investigating these options to see if it will be cheaper (maybe bit more of a mess) than buying three inverters.

 

I also do not know how three inverters connected for 3-phase need to be connected to the solar panels and batteries. Do you have to have three solar arrays that feed each inverter and three battery banks that feed off the inverters? or will one solar array feed all three inverters and the three inverters will feed one battery bank?!

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Hi Carl, thanks for the feedback. It's something that I was wondering on if it is possible to do. Hence I draw the diagram to explain my thinking. Whether the flow of things are in the correct order, I do not know and would like to get some assitance from people that know more than I do. I am investigating these options to see if it will be cheaper (maybe bit more of a mess) than buying three inverters.

 

I also do not know how three inverters connected for 3-phase need to be connected to the solar panels and batteries. Do you have to have three solar arrays that feed each inverter and three battery banks that feed off the inverters? or will one solar array feed all three inverters and the three inverters will feed one battery bank?!

 

Hi jaco_n

 

Do you want the system to act like a UPS or are you manually going to transfer between inverter(s) and ESKOM? The reason why I'm asking is that if you are going to switch over manually, you can just as well install a 4 pole changeover switch, which is available off-shelf.  If you want an automatic transfer switch you can use a suitable 4PDT contactor and connect its coil to one of the ESKOM phases - as soon as ESKOM fails, the contactor coil will be de-energised and the load will be transferred to the inverter(s).

 

Regarding the solar / battery connections: If you are going for the Axpert inverters you can install the additional cards and cables as per the "bridge" configuration and use 1 inverter per phase.  In "bridged" mode the inverters share the battery bank and PV panels.

 

Just keep in mind that the output on the 3 separate inverters will be perfectly in sync as opposed to a normal 3 phase connection where the voltage and current on the 3 phases differ by 120

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