Electrical Repair Questions? Ask an Electrician for Answers ASAP
Welcome. My name is XXXXX XXXXX would be glad to assist.
The 400 amps, is just that 400 amps. It is not per phase but total. When wiring on 3 phase, you are required to balance the load on each phase so you have uniform phases. But it still equals 400 amps total load If you have 3 phase equipment, it will draw less amperage so each phase is less than it would be if single phase.
Now, on the 120 volts, if you use transformer to step the voltage down, the 120 volt side will pull 4 times the 480 side approximately. So if you have 100 amps of 120 volt through transformer then the 480 side only sees approx 25 amps.
Gotcha, makes sense now
Using transformers on a higher voltage system allows for a much smaller service than if you had it at 120/240
So, on the first question it's just a total load of 400 amps, so you would balance the load and maybe have max ~ 133amps on each phase?
That is correct. Usually on 3 phase, you have 3 phase equipment connected so pretty much balances itself out.
Using the transformer for lighting etc, then you get 4 times the power
So would it make sense to use a 250kw generator on this service?
for 400 amps at 480 volts? generator is 3 phase 480?
Looks like from using a calculator it's probably around 300-325 amps @ 480 3 phase depending on power factor
Ok, the 400 amps at 480 volts is close to 330kw, depends on your power factor.
Yes, you were writing while I was, lol
ok cool :)
Just Let me know if anything is needed further
I think just one more, they will be running it from a CT box from the power company approx. 150 feet to where our main panel will be, what gauge wire would be used for this? and would it make more sense to run it paralleled?
Only need 4/0 copper , so I do not see any real benefit of trying a parallel feed.
The length is not an issue with the 480 comes to around 1.3% drop and you are allowed 3%
Great, thanks for all of your time, I appreciate it!
you are most welcome, glad to assist
Have a good day!