conductor sizing for VFD retrofit for submersible pump

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pick

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I just want to check my calculations for this application.The pump is 355 HP 465 volt nameplate amps not available, total motor conductor length <100 ft. The VFD is 400 Hp 480 volt 480 input amps.This is a retrofit for an existing across the line setup. The VFD will be within 30 ft running conduit length from the existing lineup. Using 400 HP for the motor with 430.6 and 430.250 I get 477 Amps then with 430.22(A) 596.25 rounded to 600A, then by 310.15 and 310.16 I'm up to 1500 MCM and I haven't applied derates yet, which I will have to do if I have more than 3 to a conduit. The input conductors, by 430.122 also come in at 600A. By combining VFD "L" and "T" conductors or parallel conductors in the same conduit derates will come into play. There will be some derate for temperature. In short the best I have come up with is
parallel 350's for the input and output in separate conduits, 4 total.

Your input would be appreciated.
 
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pick said:
I just want to check my calculations for this application.The pump is 355 HP 465 volt nameplate amps not available, total motor conductor length <100 ft. The VFD is 400 Hp 480 volt 480 input amps.This is a retrofit for an existing across the line setup. The VFD will be within 30 ft running conduit length from the existing lineup. Using 400 HP for the motor with 430.6 and 430.250 I get 477 Amps then with 430.22(A) 596.25 rounded to 600A, then by 310.15 and 310.16 I'm up to 1500 MCM and I haven't applied derates yet, which I will have to do if I have more than 3 to a conduit. The input conductors, by 430.122 also come in at 600A. By combining VFD "L" and "T" conductors or parallel conductors in the same conduit derates will come into play. There will be some derate for temperature. In short the best I have come up with is
parallel 350's for the input and output in separate conduits, 4 total.

Your input would be appreciated.
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430.122 requires the conductors to have an ampacity of 125% of the drive rating. 480 amps x 1.25 = 600 amps. Looks like 2 ckts of #350 will do the job.
 
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