Question about conductor size?

[kylelee]

If I need to install a 30kva 347/600 Y step down to 120/208 transformer. For the primary side conductor size is 30kva/ 600v=50amp? Awg 6 copper conductor ? And secondary size is 30kva/208v=144 amp? Awg 1 copper conductor?
Is this right ? And why I saw someone use just awg 8 copper for primary side?
And for what is the amp for the fuse ?


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[augie47]

Other than exempted by 240.4(F) or (G) {not applicable here} conductors must be protected in accordance with their ampacity taking 110.14 into account. #8 THHN would normally be protected by a a 40 amp or 50 amp over-current device ( 110.14 would determine which)

 

[jumper]

Is this a 3 phase transformer? If yes, you are missing 1.732 in your calculations.