If the DC power plant needs a total 3,000A @ 48VDC.
How to calculate electrical service (Amp. or kVA) at 480V/3PH to serve this plant load?
(Assuming this AC power service shall feed several rectifiers inside DC plants)...
Depends a bit on rectifier configuration* and whether it is an uncontrolled rectifier (diodes) or a phase controlled rectifier (SCRs).
*Six pulse, 12-pulse, hexaphase? Does it have an IPT? Air natural, forced air, water cooled?
The most recent we did, earlier this year, was a 7kA hexaphase job. The fourth in a row for the same customer as it happens. Water cooled.
I have just quoted for a 2kA job for that same customer. The more economic arrangement was a conventional six pulse configuration. The semiconductor cost goes up. The transformer cost goes down.