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Join Date: Apr 2011
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Change Phase Rotation for Inverters on Solar Array

08/21/2013 11:29 PM

To preface my question, let me give some background information.

On a solar energy project, we have an ABC CCW rotation coming from the utility. The inverter manufacturer wants an ABC CW rotation. We are currently set up with the proper phasing, according to the utility. There are 5 medium voltage transformers (34.5kVac-330Vac) paralleled together in a circuit. A is A, B is B and C is C, throughout. The inverter manufacturer is wanting us to swap A and C phases, in the middle of the circuit, to give the inverter skid a CW rotation. We have been producing nominal power for a few weeks as we are. My question is what would happen if we swapped A and C phases, in the middle of the circuit, to make the inverter manufacturer happy.

Our substation is 34.5kVac-230kVac. We are definitely ABC CCW from the utility.

This is my 1st solar project. I've never seen a power plant be able to sync to the grid with no sync circuits.

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Guru
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#1

Re: Change Phase Rotation for Inverters on Solar Array

08/22/2013 3:16 AM

The power doesn't care whether it is producing A electrons or C electrons. It doesn't even know about it. So, what's the problem?

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#5
In reply to #1

Re: Change Phase Rotation for Inverters on Solar Array

08/23/2013 1:41 AM

The grid certainly should care. The whole point of my question is how can an inverter receive CW rotation(after changing A and C phases) then produce the necessary CCW rotation that the grid is using.

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Guru
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#6
In reply to #5

Re: Change Phase Rotation for Inverters on Solar Array

08/23/2013 6:21 AM

CW and CCW merely suggest the viewpoint from which the local observer is making the observation. What's wrong with just swapping two of the three wires and making sure there is synchronisation like in every other grid-connected generator?

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Guru
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#2

Re: Change Phase Rotation for Inverters on Solar Array

08/22/2013 3:40 AM

Tail wags dog. Or tries to.

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Guru
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#3

Re: Change Phase Rotation for Inverters on Solar Array

08/22/2013 4:55 AM

IMO, you need to come up with the type of inverter.

Some create a CCW or CW rotation current by origin. Just test this out and give the inverter the most possible relaxation, especially when it has a transformer output. When the inverter manufacturer asks this, I would try to meet it.

Inverters might work well for a while, but can get tired of having to deal with phase- vector correction on a permanent base. The capacitors in the power generation stage will get more reverse voltage peaks when phases work reversed.

But again- make and type please and we will give you a complete answer.

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Power-User

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#4

Re: Change Phase Rotation for Inverters on Solar Array

08/22/2013 11:28 AM

a thing much similar to change a phase in any poliphasic circuit! you just need to change wires! be carefull enough if you are gonna plug power into the grid, for you are going to change the sincronism with the remaining ones! it´s a short circuit between phases after the transformer´s.

ps: I am of the field for some year´s,so I dont see what you mean with CW (or what) rotation.

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Guru
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#7

Re: Change Phase Rotation for Inverters on Solar Array

08/23/2013 10:50 AM

"We have been producing nominal power for a few weeks as we are.

My question is what would happen if we swapped A and C phases, in the middle of the circuit, to make the inverter manufacturer happy."

If you are producing power now, what's the problem?

Are you back-feeding the grid?

The power company isn't going to change their phasing just for you. Your solar array has to sync to the grid's phasing.

So, once again - If you are producing power now, what's the problem?

BA

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Power-User

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#8

Re: Change Phase Rotation for Inverters on Solar Array

08/23/2013 9:31 PM

Do not worry which is ABC or CBA. It is imaginary. You have to ensure that your load is applied same phase sequence when connected to either Source.

If it is Low Voltage system take a phase sequence tester and test directly at terminals of each source. Ensure that same rotation is applied load from both sources.

If it is high voltage system, charge the high voltage bus from each source one at a time. Select a particular PT say Bus PT of particular bus section and check phase sequence at its secondary, when bus is charged from either source.

Check auxiliaries (cooling fan, pump etc.) of invertor/ transformer etc. for proper rotation - if incorrect correct it locally, without disturbing the Correct Phase sequence already established above.

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Guru
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#9

Re: Change Phase Rotation for Inverters on Solar Array

08/24/2013 2:11 PM

YOU are the grid at the point where you let the inverter backfeed into it. You can make it easily CW or CCW by reversing 2 wires. That is what most of the responses try to tell you.

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