Conductors per phase

Dwa

How do you determine the number of conductors per phase?

From my understand, the full load amperage divided by the desired wire size's ampacity rounded up if there is a remainder.

An example: If I have a 361 Full load Amp motor from the NEC table and I calculated the motor circuit conductor protection, which the specs of the motor 300 HP, 3 Phase, 60 Hz, 480V. 125 % x 361 Amps is 451 Amps. Which Amp would I chose to divide my desire wire? I would assume to use the 451 Amps for overload protection, but the calculations don't look right if I use 600MCM/kcmil wire.