Replacing ABB commercial inverters

Z

Zee

Senior Member
Location
CA
Here's the latest Daily Puzzle:

What inverter or inverters would you replace 3 @ ABB TRIO (turned FIMER), 27.6 kW, 480VAC inverters with?

5 strings per INV.
from placard:
297 SolarWorld 280 W panels
(83.16 kW DC)
"MAX DCV: 959V
MAX AMPS per string: 9.3A"
Installed 2015.

No RSD.

all 3 INVs on a rooftop wall , so prefer no xfrmr.
 
Irregardless (not a real word) of the grounding arrangement (if any) I think you'll have a hard time finding an inverter that can connect to anything other than a grounded wye. The only one I'm aware of is solar edge, but I'm guessing you don't want to add optimizers to everything.
 
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Connecting to delta without neutral seems to be impossible.
I am seeing some brands say I can skip the neutral but it must be wye!
 
I am not knowldgeable about 480 VAC grid configurations. In particular: wye vs delta.
Can a knowledgeable person help me out here?

The existing, unreliable (and now defunct) ABB TRIO 27.6 TL inverter manual says:
“The TRIO is intended to be connected to a four-wire WYE grid; connect Neutral, L1, L2, L3, and EGC conductors.”
However, the OG retired installer swears it is "480V delta no neutral" on site.
I see the ground and neutral terminals in the (E) inverters were bonded by the installer with a field-made jumper wire. They have been that way I assume since 2015.

PXL_20220121_010622884.jpg

drive.google.com drive.google.com
So why did that work?
I.e. can I simply install any 480V inverter that demands a WYE grid, and jumper the inverter's AC output neutral and ground terminals and tie it to a 480V DELTA grid and sleep well?

I was ready to do just that...but since then I learned 2 facts that give me major pause:
1. It is true that wye contains a neutral and delta does not.......BUT but that wye also differs from delta in more fundamental ways having to do with winding configuration and consequently voltage and amps are different. Is this accurate?
2. All major mnfctrs of 480 VAC inverters insist on 480 V wye and include major disclaimers and warnings about any other config.
 
Another scenario is it could look like an ungrounded Delta. Maybe customer thinks that's what they have and they don't have or use the neutral but could in fact be grounded wye Bank on the utility end of things. In fact a utility would likely serve an "ungrounded Delta" with a wye Bank because that is what they have the transformers for (277V transformers are used for a 277/480 wye Bank).
 
electrofelon said:
I would want to verify myself. He could be just plain wrong. Also could be a terminology issue. Sometimes "delta" is used to refer to a circuit that merely doesn't have or require a neutral, but is still from a grounded wye system.
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yes! Pressing him on this now. May need to go out and verify.
 
electrofelon said:
Another scenario is it could look like an ungrounded Delta. Maybe customer thinks that's what they have and they don't have or use the neutral but could in fact be grounded wye Bank on the utility end of things. In fact a utility would likely serve an "ungrounded Delta" with a wye Bank because that is what they have the transformers for (277V transformers are used for a 277/480 wye Bank).
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Appreciated.
I understood the first half. I am mainly a residential guy - not commercial so much.

If i go out with a voltmeter and my eyeballs, how would i distinguish wye from delta?
 
Hmmm, whole can of worms. Just read this all the way thru.

Wye Inverter on a Delta Service

So, I haven’t spec’d equipment on anything this big before, and it’s looking like I might have messed up. The building has a 480 v delta service, I wired 4 solar inverters that are looking like they will only work on a Wye service. The thing that tripped me up is that the inverter manual says...
forums.mikeholt.com
 
Zee said:
Appreciated.
I understood the first half. I am mainly a residential guy - not commercial so much.

If i go out with a voltmeter and my eyeballs, how would i distinguish wye from delta?
Click to expand...
First I would look at the service equipment. Look for a neutral and a MBJ. If it still looks ungrounded, take some voltage measurements. Note you could very well still read 277v each phase to ground but have it be ungrounded. You really need a low Z meter. I would put my digital on it and see what happens to the voltage when I put my solenoid tester on it (L-G). If it ungrounded, your solenoid tester wont pull in, or if there is a lot of capacitive coupling, it may a little but the voltage will sag way down. You could also ask the Poco what they are showing for the type of service.
 
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Either the OG retired installer in incorrect about the service or the owner has just been lucky. The neutral is used just to measure phase voltage, there is no power flow. If it's an ungrounded service then it's measuring the line to ground voltage which would be floating around and most inverters would nuisance trip with a phase voltage error. But you can get lucky and have a more stable than usual line to ground voltage. It's magic.
 
I have seen three phase services with no neutral conductor but the secondary of the transformer is wye with the neutral grounded. Are you sure that this isn't what you have?
 
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ggunn said:
I have seen three phase services with no neutral conductor but the secondary of the transformer is wye with the neutral grounded. Are you sure that this isn't what you have?
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I've run into a few of these, always kind of freaks me out. I think it happens when a utility replaces an old transformer with a delta on the customer side with one that has a WYE on the customer side on an 3W service. They don't run a neutral to the customer since there is no place to land it in the existing 3W service equipment. From the customer's point of view it's still a 3W ungrounded service, so they are happy they don't have to change anything. Since there is no neutral at the service entrance equipment I still treat it as an ungrounded service for the PV system interconnection.
 
pv_n00b said:
Since there is no neutral at the service entrance equipment I still treat it as an ungrounded service for the PV system interconnection.
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How would you do that? If it were truly an ungrounded delta service, most three phase inverters cannot connect to it.
 
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