480V 3 wire to 4 wire transform

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480 delta to 480/277 Y transformer. A separately derived secondary. Typical application would be the lighting transformer.
 
freddyjones39 said:
Sorry, 480 Wye without a neutral to 480 Wye with a neutral.
Click to expand...
480V 3Ø 3W is often called delta, but it can be supplied by a 480Y/277V 3Ø 4W wye system as well as a 480/240V 3Ø 4W delta high-leg system, as well as a 480V 3Ø 3W ungrounded or corner-grounded system. Which do you currently have? What's on the nameplate of the supplying transformer(s)?

If you already have a 480Y/277 3Ø 3W system, just add the fourth conductor and be done with it.
 
Smart $ said:
480V 3Ø 3W is often called delta, but it can be supplied by a 480Y/277V 3Ø 4W wye system as well as a 480/240V 3Ø 4W delta high-leg system, as well as a 480V 3Ø 3W ungrounded or corner-grounded system. Which do you currently have? What's on the nameplate of the supplying transformer(s)?

If you already have a 480Y/277 3Ø 3W system, just add the fourth conductor and be done with it.
Click to expand...

Should it not be an earth grounded fourth conductor????
 
Going from a 480V 3Ø 3W to a 480V 3Ø 4W, 15kVA.

I feel a little ridiculous about even starting this thread. Thanks everybody for your patience! I will just drop a transformer in primary 480 Delta secondary 480 Wye.

Problem solved (it just wasn't clicking that I just had a Delta on my hands)...:blink:
 
A 'zig-zag' transformer is not suitable for this application.

Such a transformer will 'derive' a neutral, but you won't be able to use the neutral to supply the load.

Imagine that the supply system is an ungrounded delta. Then you could use a 'zig-zag' transformer, and derive a neutral. But when you ground the neutral (required if you want to actually use the neutral conductor) then you ground the _entire_ system, not just the loads served.

Imagine that the supply system is a grounded wye, but only three wires were brought to the use location. If you use a 'zig-zag' transformer to 're-derive' the neutral, when you ground it you will essentially have a second ground-neutral bond. Huge currents will flow through this bond if there is any unbalance in the feeder to the transformer.

-Jon
 
winnie said:
Imagine that the supply system is a grounded wye, but only three wires were brought to the use location.
Click to expand...

And where did that come from? OP said that there was no neutral. I can "imagine" all sorts of things.
 
I apologize for not stating my assumptions.

The OP has 480V without a neutral and needs to supply a small load.

I made the assumption that the 480V system was relatively large, and that they wanted a transformer sized for the load.

One of the many possibilities is that they have an ungrounded 480V system which they are willing to ground. In this cause they could use a suitably sized zig-zag transformer to derive a neutral for the entire system, which they could then ground and use to supply a grounded conductor.

What they could not do is use a small zig-zag transformer sized for the small load, and then use this derived neutral to supply the small load only.

A neutral serving a load is required to be grounded (bonded to the GES). If you ground the neutral of the zig-zag transformer than you are grounding the _entire_ system. While in theory the zig-zag transformer could derive a neutral which they _don't_ ground, that is not permitted by code.

I am willing to learn; is there some way that I am missing where they could use a zig-zag transformer sized for the load?

-Jon
 
Humble request......

Humble request......

Would OP please draw a schematic on a piece of paper and take a pic with cellphone. Then just post it so all are on same page here.

It is a very important thread and it is a pity to see it misconstrued.
 
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