|The image is of a bank of (3) 250 Kva transformers wired 3 phase-4 wire 480/277V Y. The hot conductors are because it is a really terrible installation. Bad enough that the secondary phase conductors were reduced to the transformer from the service drop, but the common conductor (hot) were even further reduced. The transformers have a capacity of 900 amps. The common conductor at the transformer taps carry the same current as the line conductors. Judging from 25' those conductors looked to be good for about 150 amps. The load that day may have been around 400-500 amps.