What affects the physical size of a power Xfmr?

[Redskinsdb21]

Hello Fellow Engineers,

I am currently working on a project to replace several power Xfmrs that are located in vaults. So an issue is whether or not the new Xfmrs will even fit in an existing vault or vault will need expanded. I have asked for preliminary quote with dimensions. However, I got to thinking if my client would liek to increase Xfmr size (KVA rating) then how much larger would the Xfmr be? So my question is, what affects the physical size the most? Is it KVA rating? If voltage levels are higher does than increase Xfmr size much or is it mostly KVA rating?

Thanks!

 

[waross]

The size depends mostly on the KVA rating, all else being equal.


--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[bacon4life]

In addition to kVA, high efficiency requirements can require a significant increase in size. In the USA, it might not be possible to purchase the exact same size/weight of transformer as an older installation.

Are you thinking of changing voltage classes (i.e. 15 kV to 35 kV?)? For transformers with a very small kVA rating compared to the voltage class of the HV winding, the minimum size is limited by insulation dimensions on the HV winding. I am not sure how the dimensions would be impacted for transformers with typically kVA ratings.

 

[waross]

Time to spend a couple of hours Googling and reading transformer spec sheets.

--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[Redskinsdb21]

bacon4life (Electrical)22 Aug 23 17:18
In addition to kVA, high efficiency requirements can require a significant increase in size. In the USA, it might not be possible to purchase the exact same size/weight of transformer as an older installation. Yeah, I am aware of the DOE efficiency requirements. We are actually doing to subs both with Xfmr vaults.

Are you thinking of changing voltage classes (i.e. 15 kV to 35 kV?)? For transformers with a very small kVA rating compared to the voltage class of the HV winding, the minimum size is limited by insulation dimensions on the HV winding. I am not sure how the dimensions would be impacted for transformers with typically kVA ratings. We are pretty much at same voltages but looking to increase KVA rating in one of the Subs. The other KVA rating and Voltages are same, but I am concerned even at that if it will fit into vault.