Voltage drop.

[jbolen]

I have 75 hp motor on 200 amp breaker due the long distance we install 350 mcm What size grounding conductor should we use in the cable tray.

 

[masterinbama]

#2

 

[xformer]

See 250.122(B)

 

[Dsg319]

I have 75 hp motor on 200 amp breaker due the long distance we install 350 mcm What size grounding conductor should we use in the cable tray.

Your EGC is sized per the OCPD and increased proportionally in percentage to the phase conductors.

 

[don_resqcapt19]

Assuming a 3 phase 460 volt motor the required conductor size is 2 AWG. That has a cm of 66360, and you used a conductor with a cm of 350,000 so you have increased the wire size by a factor of 5.27. The required EGC from Table 250.122 for a 200 amp OCPD is 6 AWG with a cm of 26,240. The application of the rule in 250.122(B) will require an EGC with a cm of not less than 138, 285, requiring the EGC to be 3/0.