What size conductors are needed for a 450 amp,three phase,600 volt electrical system,these conductors would be for the primary side of a three phase transformer

HOw did you come up with a 600 volt electrical system? Your conductor size would not only depend on the amount of amps but also the distance you will need to run these conductors.

Apparently Jerro is not aware that there are 600 volt 3 phase systems in existence in industrial applications.Jerro is correct that distance needs to be considered when sizing wire to eliminate voltage drop.

Assuming the terminations are rated 75 Deg C, which is typical, 450 amps would need #700 MCM copper wire with THHN/THWN of XHHW insulation, which can handle a maximum of 460 amps.

However, if the 450 is the connected load, the amp rating of the wire size should need to be increased 25%.

This is not a DIY project. Where is the qualified electrician responsible for this project?

Tk, I am aware of a 600volt system, I was just trying to get a clarification from the poster as to what he had. To me if someone ask that kind of questions he should have the knowledge of knowing what size conductors to use.