277 to Nutral needed

[Toros]

Hi
I have the existing 1200A service @ 480v, 3-wire
now the new lighting load that requires 277V input are waiting for my decision

What type dry xfrmer do I need????

I am thinking ,
480v , 3-wire 3ph. as primary
480/277v , 4-wire, 3ph. as secondary
(And used only "H" & "0" terminals of primary side for supplying the loads,
not using secondary terminals) ???????

Thank you

 

[Toros]

277v Nuetral needed

277v Nuetral needed

Hi
instead of using a transxfrmer, can I get 277 neutral from the system grounding of existing 480v, 3-wire (that has no nuetral)
to supply 277v lighting loads ??????

Thanks

 

[victor.cherkashi]

Electrical power is close loop, if current come out from one transformer (system) it cannot go other system. The question is not clear

Sent from my Nexus 5 using Tapatalk

 

[Little Bill]

Hi
instead of using a transxfrmer, can I get 277 neutral from the system grounding of existing 480v, 3-wire (that has no nuetral)
to supply 277v lighting loads ??????

Thanks

If I understand your question the answer is no. It would be the same as a 120V/240V system. You would be putting unwanted current on the EGC of the system if you use the EGC as a neutral.

 

[ActionDave]

I merged these two threads since they have the same title and are related.

 

[mach531]

I've had a similar application before. We used a dry type, indoor, isolation transformer like you suggested (480V delta primary - 480/277 wye secondary) but your load would be connected to secondary terminals (X1, X2, X3) including your neutral on X0. Presuming you ground X0 of course.

It's just like a step down transformer except your phase-phase voltage ratio is 1:1.

 

[petersonra]

Hi
I have the existing 1200A service @ 480v, 3-wire
now the new lighting load that requires 277V input are waiting for my decision

What type dry xfrmer do I need????

I am thinking ,
480v , 3-wire 3ph. as primary
480/277v , 4-wire, 3ph. as secondary
(And used only "H" & "0" terminals of primary side for supplying the loads,
not using secondary terminals) ???????

Thank you

If I understand it, you have 480V delta at present and need some amount of 277V to run some new lights on.

If you only need a moderate amount of 277V, you can get a single phase transformer 480 to 277V.

If you need more than what is appropriate for a single phase xfmr, you can get a 3 phase 480 D to 480 Wye transformer.

In either case, you will be creating a separately distributed system and need to be aware of the requirements for such a system and will be feeding the new 277V loads off the load (secondary) side of the xfmr.

However, before I did any of this I would check and see if maybe you actually have 480V Wye and they just did not run the N past the service point because it was not needed.

 

[dkidd]

Separately derived system.

 

[iceworm]

Hi
I have the existing 1200A service @ 480v, 3-wire
now the new lighting load that requires 277V input are waiting for my decision

What type dry xfrmer do I need???? ...

Adding to previous posts. The norm is to scatter around the plant, 480D/480Y , 75kva, xfm, feeding a 100A/125A 3ph, 4w panel. Feed xfm from a local 480, 3ph, 3W panel

... I am thinking ,
480v , 3-wire 3ph. as primary
480/277v , 4-wire, 3ph. as secondary
(And used only "H" & "0" terminals of primary side for supplying the loads,
not using secondary terminals) ??????? ...

I'm completely clueless on what you have in mind with this.

Couple of other things:
As petersonra suggested, maybe there is an available neutral for the existing system. However, I would not expect this. If the existing service is 480Y (likely), the neutral was only run to the first disconnect.

One other thing: If available, consider 480 ballasts, wire to existing system Line-to-Line. This works really well if the lights are always on or switched in mass (industrial). Office buildings - not so good, you will need contactors.

ice