Motor Feeder Calculations(using 99 NEC)

[jw441]

400 HP Motor/Pump, 1800 SYNCH SPD(rpm), 3 PHASE, 60 HZ, 460 VOLT, 445 FLA, 2900 LOCK ROTOR, INS CLS & KVA/HP CODE "F", DESIGN "B", 89 FL(pwr factor), US ELEC MTRS, PENTAIR PUMP GROUP.

BLUE PRINT CALLS OUT(using THHN copper): 3 - 350kcmil, 1 - #1/0 GND, 2 - 3.5" C (parallel feed) - C/B 800 AF / 800 AT to VFD(controller), then back out again(parallel feed of same) to Motor/Pump.

MY CALCULATIONS: 3 - #3/0, 1 - #1 GND, 2 - 2" C (parallel feed) from C/B 600 AF / 600 AT to VFD(controller); then 3 - 250kcmil, 1 - #1 GND, 2 - 2.5" C (parallel feed of larger) from VFD to Motor/Pump.
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200 HP Motor/Pump, 1800 SYNCH SPD(rpm), 3 PHASE, 60 HZ, 460 VOLT, 224 FLA, 1309 LOCK ROTOR, INS CLS & KVA/HP CODE "F", DESIGN "B", 87.6 FL(pwr factor), US ELEC MTRS, PENTAIR PUMP GROUP.

BLUE PRINT CALLS OUT(using THHN copper): 3- 350Kkcmil, 1 - #2 GND, 1 - 3" C (single feed) - C/B 600 AF / 500 AT to VFD, then back out again (single feed of same) from VFD to Motor/Pump.

MY CALCULATIONS: 3 - #3/0, 1 - #4 GND, 1 - 2" C (single feed) from C/B 300 AF / 300 AT, to VFD(controller); then 3 - 250kcmil, 1 #4 gnd, 1 - 2.5" C (single feed of larger) from VFD to Motor/Pump.
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PLEASE ASSIST AND/OR ADVISE TO ANY/ALL.
ANY/ALL CORRECT ADJUSTMENTS(99' NEC) ARE APPRECIATED.
THANK YOU - FRATERNALLY, JW441




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[don_resqcapt19]

What is the input rating of the VFDs? You need to know that to size the wire to the drive.
Don

 

[bob]

400 HP Motor/Pump, 1800 SYNCH SPD(rpm), 3 PHASE, 60 HZ, 460 VOLT, 445 FLA.

AS Don says you need to rating of the VSD drive. The conductor must match the ampacity of the drive. But that aside, from table a 400 hp FLA = 477 amps. 2 - 3/0 will not cut it. At the very minimum 477 x 1.25 = 596 amps. 2 - 3/0 = 400 amps. 2 - 350 = 620 amps. How did you come up with 3/0?

200 HP Motor/Pump, 1800 SYNCH SPD(rpm), 3 PHASE, 60 HZ, 460 VOLT, 224 FLA

From the table a 200 hp FLA = 240 amps.
240 x 1.25 = 300 amps
1 # 350 = 310 amps. 1 # 3/0 = 200 amps.

MY CALCULATIONS: 3 - #3/0, 1 - #4 GND, 1 - 2" C (single feed) from C/B 300 AF / 300 AT, to VFD(controller); then 3 - 250kcmil, 1 #4 gnd, 1 - 2.5" C (single feed of larger) from VFD to Motor/Pump.

I don't see how you can use a 300 amp breaker for this load.