over 500 hp

[tesi1]

when calculating the feeder size and overcurent protection on a 480 volt 700 hp motor, table 430.250 only goes to 500 hp. do we simply just use the info
off of the motor tag ?

 

[Rock86]

If you have a name plate with current rating, use that information for your calculations or get specifications from manufacturer if able as well.

 

[Jraef]

In the little EASA pocket handbooks, the cheat-sheet version of 430.250 has a footnote saying that for 460V above 500HP, you use HP x 1.2 (for 230V over 200HP you use HP x 2.4 and for 575V over 500HP use HP x .96), all based on motors being 4 pole. 2 pole motors have lower FLC values, but when you get to 500HP+, you can run into higher pole count motors quite often, and their FLC values will be higher. So it's always best to use the nameplate values to be sure.

I recently ran into a situation where someone bought VFDs for some 350HP pumps, but failed to notice that they were 12 pole motors (560RPM), so the motor nameplate FLC was 438A, whereas the 350HP VFD was sized as 361A. And of course they didn't discover the mistake until after they mounted and connected the VFDs, then tried to set the motor FLA higher than 361A and couldn't. Oopsie...

 

[Besoeker3]

In the little EASA pocket handbooks, the cheat-sheet version of 430.250 has a footnote saying that for 460V above 500HP, you use HP x 1.2 (for 230V over 200HP you use HP x 2.4 and for 575V over 500HP use HP x .96), all based on motors being 4 pole. 2 pole motors have lower FLC values, but when you get to 500HP+, you can run into higher pole count motors quite often, and their FLC values will be higher. So it's always best to use the nameplate values to be sure.

I recently ran into a situation where someone bought VFDs for some 350HP pumps, but failed to notice that they were 12 pole motors (560RPM), so the motor nameplate FLC was 438A, whereas the 350HP VFD was sized as 361A. And of course they didn't discover the mistake until after they mounted and connected the VFDs, then tried to set the motor FLA higher than 361A and couldn't. Oopsie...

I generally just use the nameplate rating.

 

[paulengr]

The IEEE standards for over 500 HP do not give FLA. Use name plate. NEMA values are based on kw with a power factor (0.85 if I recall).