Using neutral from another transformer to get 277 from a 480v Delta transformer

As Aabeck points out, there is a VERY SPECIFIC type of transformer you can add to the system to do what you are proposing. There is a part of me that doesn't even want to refer to that as a transformer but what else would you call it?

However, if you are talking about using the neutral of a 480V/240V delta/wye isolated winding transformer as the neutral for the 480V delta system, that won't work for the reasons stated; namely the primary and secondary are still isolated from each other. The neutral means nothing to the primary side.

Keith

Timeismoney08 said:

No, they do not need all of the phases for using with the neutral. Just one of them.

Components that need it are contactors, relays, etc.

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lfe said:

If it is a small consumption you can install a small 480V/277V transformer although It seems strange that you use 277V for the coils of a contactor or relay, better to use a 480/120V trafo or 480/24V ?

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Exactly !
Get a single-phase transformer suited for the job. Tie one leg on the secondary side to earth, that becomes the neutral on that side.
Or ... drops single-phase AC control altogether and go 24 VDC. These days it is completely standard to go from 3-phase AC to 24 VDC by a suitable PSU.

Not an "Odd thing to ask ", but criminal?

Timeismoney08 said:

This is a odd thing to ask and I'm sure it's not allowed, but I'm curious about the problems and effect from taking g a 480v Delta system (no neutral), adding a xformer that has a neutral, and using the transformers neutral with the preexisting 480v Delta system.

For the record, the second xformer is a step down to 240, but let's just pretend we are borrowing a neutral from another system.

Is this any better or worse than just using ground as the neutral?


Thanks!

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Timeismoney,
I am not sure what your job scope is, or what your current task is, but the answer is no.

If you are asking the question, you have flagged yourself to be unqualified to be making electrical installations on separately derived systems, and are not following NFPA70, nor NFPA 79.

As an attempt to answer your question "What would happen?'

Most likely, there would be LETHAL voltages and current running through metallic equipment that human life and loved family members, dad, moms, children, are exposed to.

Please contact a local qualified electrician to help get your project on task.

Thank You

Plastic

Plastic is very correct.


If you use the ground as a neutral there is going to be current going through the ground system. This would energize the ground between your connection and the ground rod. The current would travel through the metal control panels, the frame of the machine, the ground wires going to the motors, and every ground wire and connection. If something happened to create a bad bonding connection somewhere along the line there would be a definite voltage on the not-really-grounded side.



Having current going through any part of the ground circuit is BAD.


And, I agree that a Zig-Zag transformer isn't really a transformer, more of a 3 phase autoformer.

Well thank you for the replies, but I seriously hope next time you read the entire posting before accusing me of doing something wrong.

I have made it very clear that I did not EVER recommend or allow such an installation to occur. I was purely inquiring on what does happen if it was wired that way as it was done before I arrived.

If I have not made it clear, let me say it again.......I did not and would never wire things this way. I am purely asking for a better understanding on what happens.

Sorry for terse response

Timeismoney,

Sorry for sounding accusatory, I read the entire post, and understood that no failed installations were made under your directive.

You asked "what would happen", I answered "LETHAL voltages and currents will be present in the grounding system".

I will soften this up by stating that electrical loads should be served by a single circuitous path from transformer to load via only ungrounded and grounded conductors, and never on grounding conductors.

I guess I jumped overboard, due to seeing many failed installations where grounded conductors (neutral), and grounding conductors get interchanged, and mixed.

Again, please understand I am only trying to be helpful.

Best regards

Plastic

Thank you for explaining it to me.