320 hp motor current

[Electriman]

Greeting,

What current should I consider for 320 hp induction motor at 460 V? There is no number between 300 hp to 350 in NEC table 430.250.

 

[retirede]

As a rule of thumb, you could interpolate between the 300 & 350 values, but often a nonstandard HP rating means that the motor design may have other unique aspects causing the FLC to be out what is considered normal range.
Best bet is to get the nameplate data for your specific motor.

 

[Electriman]

I agree with interpolating. But name plate is normally less that what NEC has on table 430.250

 

[Jraef]

The NEC tables are purposely conservative and are just for selecting conductor sizes and OCPDs, allowing for room to change to a different motor that may have a different nameplate value. Just use 350HP, you can’t go wrong. For the OL Protection though, you still need the motor FLA from the nameplate.