Neutral

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Alwayslearningelec

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Estimator
If I'm feeding the primary side( 277/480v) from a 3P breaker in a panel is a neutral?
I believe neutral is needed/generated on the secondary side of xfrmr and not primary.
Can you explain why or why not the neutral would be needed.

It's a a general 45 kva xfrmr.

THanks.
 
480/277 describes a wye system. Is that the spec of the transformer or the service your feeding it from? If the transformer's primary spec is 480V delta then that does not need a neutral on the primary side. It's fine to feed a delta primary transformer from a wye system. If the transformer primary spec is 480/277 wye, my understanding is that would be unusual and you may want to inquire if you have the correct transformer.

Who drew up the design and what does the diagram say? What is the application?

I'm afraid calling it a 'general' transformer doesn't clarify anything.
 
I’m assuming you have a 45 Kva 480 delta step down transformer to a 208/120 wye. The primary would be the 3 wire 3 phase 480 volt. The secondary would be a 4 wire 3 phase 120/208 wye.

What exactly are you trying to figure out, why the primary does not need a neutral, why the secondary has a neutral, please clarify?
 
jaggedben said:
480/277 describes a wye system. Is that the spec of the transformer or the service your feeding it from? If the transformer's primary spec is 480V delta then that does not need a neutral on the primary side. It's fine to feed a delta primary transformer from a wye system. If the transformer primary spec is 480/277 wye, my understanding is that would be unusual and you may want to inquire if you have the correct transformer.

Who drew up the design and what does the diagram say? What is the application?

I'm afraid calling it a 'general' transformer doesn't clarify anything.
Click to expand...
There is no design. It's a temp power situation.
Attached is the xfrmr we have laying around and might use. First time reading xfrmr nameplate...lol.
I can't even tell if it's 277/480v primary. I do see a 480 reference then a 208y/120 but again still can tell how that indicate which voltage is primary or secondary.
 

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Canton said:
I’m assuming you have a 45 Kva 480 delta step down transformer to a 208/120 wye. The primary would be the 3 wire 3 phase 480 volt. The secondary would be a 4 wire 3 phase 120/208 wye.

What exactly are you trying to figure out, why the primary does not need a neutral, why the secondary has a neutral, please clarify?
Click to expand...
Ah so I think you just answered my question about not knowing the primary or secondary voltage....I guess where it says 'y' that's the secondary side?

I'm asking about whether a neutral is required in my situation and why...or why not.
 
jaggedben said:
480/277 describes a wye system. Is that the spec of the transformer or the service your feeding it from? If the transformer's primary spec is 480V delta then that does not need a neutral on the primary side. It's fine to feed a delta primary transformer from a wye system. If the transformer primary spec is 480/277 wye, my understanding is that would be unusual and you may want to inquire if you have the correct transformer.

Who drew up the design and what does the diagram say? What is the application?

I'm afraid calling it a 'general' transformer doesn't clarify anything.
Click to expand...
A few questions and thank you .
A WYE system is always 277/480? Why? Lol

Can you have 277/480v delta?
 
Canton said:
I’m assuming you have a 45 Kva 480 delta step down transformer to a 208/120 wye. The primary would be the 3 wire 3 phase 480 volt. The secondary would be a 4 wire 3 phase 120/208 wye.

What exactly are you trying to figure out, why the primary does not need a neutral, why the secondary has a neutral, please clarify?
Click to expand...
So the needing(or not) of a neutral on the primary side depends ONLY on the transformer you’re using ?
 
horsegoer said:
A few questions and thank you .
A WYE system is always 277/480? Why? Lol

Can you have 277/480v delta?
Click to expand...

No. You can theoretically have any voltage in either configuration.

208y/120 is a very common wye voltage.

On the delta, if you were to center tap one of the windings to create a neutral, you would have a 480d/240 with a 277v high leg.
 
horsegoer said:
Thanks. This stuff is confusing to understand...lol
Click to expand...
Actually, it's not all that bad once you wrap your head around the basics of three phase systems. Ohm's Law and the other equations still work.
 
horsegoer said:
A few questions and thank you .
A WYE system is always 277/480? Why? Lol

Can you have 277/480v delta?
Click to expand...
You can have a 480 delta, but usually it is corner grounded (one phase is taken to ground, or a ground fault monitor/detector if not) No neutral. Common in industrial, but not in commercial.
 
horsegoer said:
Your right but what a PIA. Everything nowadays is digital downloads.
Click to expand...
I agree. I got the mike holt grounding book and dvd with a grand plan to show some clips of the dvd at some of our internal training , I shelved it for awhile and now non one’s computer has a dvd drive. I know it’s easy enough to get one but mostly because of laziness on my end I never followed up and now it’s on the shelf with old dvds and floppy discs of manufacturers product info when that was a thing. The book however is pretty worn down and used all the time. Great book.
 
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