150 kva step up transformer

[tico17]

Hi Hope every one is good,

question i have to get a transformer 150 kva 120-208Y primary to 480-277Y secondary, its for a temporary power but i can't find it anywhere used, since its temporary but getting inspected i saw a few that says 480-277 primary/120-280Y secondary, can they be backfeed and will it give full rating on transformer? and is this acceptacle

 

[infinity]

Lately I've seen labeling on transformers that states whether or not it can be wired in reverse for step-up. For temp power we wire Delta/Wye transformers in reverse and corner ground them. Since you have a Wye secondary you won't even need the corner ground.

 

[tico17]

Lately I've seen labeling on transformers that states whether or not it can be wired in reverse for step-up. For temp power we wire Delta/Wye transformers in reverse and corner ground them. Since you have a Wye secondary you won't even need the corner ground.

so my primary voltage will be 208v delta since i wont be running a neutral or that still 120-208Y? sorry for this question but i want to be sure

 

[infinity]

so my primary voltage will be 208v delta since i wont be running a neutral or that still 120-208Y? sorry for this question but i want to be sure

You stated that the primary is Wye but even so you still only need to bring the 3Ø conductors and no neutral to the primary.

 

[tico17]

You stated that the primary is Wye but even so you still only need to bring the 3Ø conductors and no neutral to the primary.

yes its a Y system, i just got confused when you said delta since i seen a few transformers that are 208 delta to 480-277y

 

[infinity]

yes its a Y system, i just got confused when you said delta since i seen a few transformers that are 208 delta to 480-277y

OK just for clarification you have a Wye/Wye transformer and the 208 volts for the primary is from a 208Y/120 system or is it a Delta/Wye transformer?

 

[tico17]

OK just for clarification you have a Wye/Wye transformer and the 208 volts for the primary is from a 208Y/120 system or is it a Delta/Wye transformer?

its a 120/208Y 3phase and we need 277/480y 3 phase

 

[tico17]

OK just for clarification you have a Wye/Wye transformer and the 208 volts for the primary is from a 208Y/120 system or is it a Delta/Wye transformer?

i just called jefferson transformers but somehow i got connected to SOLA HD transformer, he said in these transformers i can use a 208 delta and not to use neutral from my Y system and i will still have 480/277Y, does that sound right?

 

[infinity]

i just called jefferson transformers but somehow i got connected to SOLA HD transformer, he said in these transformers i can use a 208 delta and not to use neutral from my Y system and i will still have 480/277Y, does that sound right?

Yes, the transformer is 208-480Y/277 (Delta/Wye) but the primary side (Delta) is fed from a Wye system. Simple.

 

[Jraef]

Even though the 208V side may be a Wye system feeding the transformer, THAT TRANSFORMER would be connected using the 3 phase conductors only; i.e. do NOT ground the X0 terminal on the 208V side.

You DO want to ground the X0 terminal on the 480 side, IF THERE IS ONE. Often there is not and if that's the case, then you would have to either corner ground it, or supply ground monitoring for it.

And to be clear, per the 2014 NEC, that transformer must now state, SOMEWHERE, that it is suitable to be used for step-up (actually what it says is connecting to the secondary as the source). It doesn't have to say it on the transformer nameplate itself, but that helps when an AHJ asks to see it, otherwise you have to be Johnny-on-the-spot with a data sheet proving it. This is covered in 450.11 (B) and is a little less direct than what I just said, but most AHJs are treating it this way now. YOU have to demonstrate that in connecting the source to the secondary, you are following the manufacturer's directions to do so and if there is nothing saying specifically that you can, they are interpreting that you cannot.

 

[Oldapprentice]

Maybe one of you guys can tell me what class OA stands for on a older transformer. I know it has to deal with cooling of the transformer but I need to know what it is abbreviated for.

 

[GoldDigger]

Maybe one of you guys can tell me what class OA stands for on a older transformer. I know it has to deal with cooling of the transformer but I need to know what it is abbreviated for.

Welcome to the Forum!
Please do not:
1. Hijack an existing thread instead of starting your own with a new question.
2. Make multiple posts with the same question in different places.

Anyone who has an answer for your question can join this thread.

 

[tico17]

Yes, the transformer is 208-480Y/277 (Delta/Wye) but the primary side (Delta) is fed from a Wye system. Simple.

this is where i get lost, but after asking a few knowledge persons i realize that my primary is 208v (not 120-208v) and it will be hook up as delta but some people tell me that is a YY transformer and it will be hard to get a transformer like that.

 

[GoldDigger]

this is where i get lost, but after asking a few knowledge persons i realize that my primary is 208v (not 120-208v) and it will be hook up as delta but some people tell me that is a YY transformer and it will be hard to get a transformer like that.

Just because the source is a wye, you do not need a wye primary or a delta primary specifically. In fact with a wye source and a wye primary you may not want to connect the primary neutral.

Sent from my XT1585 using Tapatalk

 

[infinity]

this is where i get lost, but after asking a few knowledge persons i realize that my primary is 208v (not 120-208v) and it will be hook up as delta but some people tell me that is a YY transformer and it will be hard to get a transformer like that.

There are two different components which can be confusing, there's the system you're using and then there's the coil arrangement of the transformer.

The system is a Wye system where the voltage is 208Y/120 volts.

The transformer has three primary coils that can be wired in a Wye or Delta configuration. Delta is the more common for the primary and it doesn't matter that the system feeding the primary is a Wye system.

As long as you feed it with 3Ø, 3 wire, 208 volts you're good.

 

[tico17]

There are two different components which can be confusing, there's the system you're using and then there's the coil arrangement of the transformer.

The system is a Wye system where the voltage is 208Y/120 volts.

The transformer has three primary coils that can be wired in a Wye or Delta configuration. Delta is the more common for the primary and it doesn't matter that the system feeding the primary is a Wye system.

As long as you feed it with 3Ø, 3 wire, 208 volts you're good.

great thanks, its easier to look for one like this, before i did not find any with 120-208v primary, thank you guys for all your knowledge and experience

 

[LarryFine]

The transformer has three primary coils that can be wired in a Wye or Delta configuration. Delta is the more common for the primary and it doesn't matter that the system feeding the primary is a Wye system.

I know what you mean, but to actually wire such a transformer as a Delta would place 208v across each 120v winding.

 

[cortgal]

Yes, the transformer is 208-480Y/277 (Delta/Wye) but the primary side (Delta) is fed from a Wye system. Simple.

if the primary side (delta) is fed with a wye system what do you do with the neutral from the wye system ? ground it? or join to Xo of the secondary wye

 

[ActionDave]

if the primary side (delta) is fed with a wye system what do you do with the neutral from the wye system ? ground it? or join to Xo of the secondary wye

You don't run a neutral to the primary side of a transformer. You don't need it and no good will come from trying to hook it up to anything.