480 Delta from utility; neutral choices & consequences.

[Open Neutral]

I'm look at the electrician's plans for a residence being fed by PGE with 480 delta.

There will be 3 grid-tie PV-fed inverters installed, then a long cable run, a 480delta:208/120 wye and the loads.

It's been a long time since I thought above 208; so I've been reviewing very dusty memories from ELT 443 w/Prof Klingshirn, as well as reading other sources.

 

[LarryFine]

Opie, welcome to the forum!

What's the question?

 

[Open Neutral]

Opie, welcome to the forum!

What's the question?

Much embarrassment; an inglorious start, and no question. Somehow this submission got away from me long before I finished it, much less proofed it. And then I got a call telling me basic facts were not what I thought.

"These aren't the droids you want..."

 

[zog]

Much embarrassment; an inglorious start, and no question. Somehow this submission got away from me long before I finished it, much less proofed it. And then I got a call telling me basic facts were not what I thought.

"These aren't the droids you want..."

Welcome anyways, stick around you will learn a lot here, like "These aren't the droids you're looking for"

 

[CCDTHOMAS]

Feeding a transform backwards

Feeding a transform backwards

Ive got a 480v primary to 120/208V secondary feed backwards, only feeding three phase pump motors, the problem is that the control boards for the pumps need a neutral, is there any way to reconfigure this transformer to make it produce a neutral on the primary side. This is a mission critical installation, and the possibility of getting the correct transformer is months away. Any suggestions.

 

[Sierrasparky]

Ive got a 480v primary to 120/208V secondary feed backwards, only feeding three phase pump motors, the problem is that the control boards for the pumps need a neutral, is there any way to reconfigure this transformer to make it produce a neutral on the primary side. This is a mission critical installation, and the possibility of getting the correct transformer is months away. Any suggestions.

I'm guessing this is a Delta Primary? I would say no unless one of the windings is center tapped.

 

[wireguru]

is it possible to just use a small control transformer to supply the control boards?

 

[winnie]

1) The correct transformer can almost certainly be had quickly if enough $$ are brought to bear. Just how many KVA are you talking, and where are you located? Someone here might be able to point you to the transformer that you need sitting on a shelf.

2) A 'zig-zag' autotransformer can be added to a delta system to derive a neutral. This is often done to derive a neutral for grounding purposes. If the maximum neutral current is very low, then this can be a viable approach.

3) As wireguru mentions, if you only need the neutral for controls, then you can use a small 'control transformer' to provide power for these controls.

4) You might consider banking single phase transformers to provide your desired 208 to 480/277V transformer.

-Jon