wiring calc

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dm9289

Industrial Maintenance Electrician
Location
Pennsylvania
Occupation
Industrial process repair/ maintenance Electrician
I have a 3 phase 480v 520a load and I wanted to calculate wire size by tray and by conduit ithink I am correct please confirm

Either case this is a continuos load so 520 x 1.25= 650a cable required

conduit with paralleled conductors i determined 2x700kcm per phase (6 total) thhn =1040a based on 650a needed

I multiplied 1040a x .82 temp correction 114degrees=852.8
then 852.8 x .80 for 6 current carrying conductors in raceway= 682.24 which is good for 650A ????



In cable tray still 650A required
used 2-500kcm thhn cables per phase (6 total) with their free air rating 2*700=1400A
Per 392.80A(2)b derated by.65 1400 x .65=910
for temp 114 degrees derated by.82 =746????

I believe I am correct could someone please confirm or correct me
Thanks
 
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