Transformer sizing

[vixelectric]

I have a property that has 480 volt/100 amp service with an existing 25kva transformer that's feeding a 125amp panel. I need to know what I need to do, to convert it to a 200 amp panel.
Thanks,
Victor

 

[charlie b]

Is the secondary a three phase, 120/208 volt distribution? If so, then a 200 amp panel would need a 75 KVA transformer, and that would use up almost all of the 100 amps available at the 480 volt level.

 

[vixelectric]

The secondary will be a 120/240 4-wire, 200 amp panel.
Do you know of a link to a graph or a chart somewhere, so I can use it in the future for conversions.

 

[brian john]

120/240 4-wire, this is a Hi-leg delta? A-B 240, B-C 240, C-A 240 A-Neutral 120, C-Neutral 120, B-neutral 208?

 

[vixelectric]

120/240 4-wire, this is a Hi-leg delta? A-B 240, B-C 240, C-A 240 A-Neutral 120, C-Neutral 120, B-neutral 208?

Sorry, I misspoke... it's for residential. 120/240 single phase. I said 4-wire because I was counting the ground. So, what would the transformer be to go from 480volt (I don't know how many wires) to 200 amp panel?
Thanks!

 

[charlie b]

Here's the math: 200 amps times 240 volts is 48,000 VA. The next higher standard transformer rating is 50 KVA. The primary side would need two ungrounded conductors and a ground wire. That is generally written as 2W + G, or something to that effect.

Is the 480 volt service feeding any other loads? I ask because 200 amps at 240 volts is the same as 100 amps at 480 volts. So this one 200 amp panel will use up all of the available 100 amps from the service.