kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
Yes, I know about the NEC specifying conductor ratings for motors and the 125% rule. I don't wish to upset or alienate anyone but those regs seem a bit antiquated to me. We designed high speed motors for various applications that had efficiencies in the high nineties. Using conductors for say, a 55kW (75hp nearest?) per NEC would be significant overkill.
Anyway, as you can see, for much of what we did the NEC wouldn't apply. Ships, 132kV fed arc furnaces.......
Tables used for determining rated current have some wording at the table header - majority of what it there only applies to motors with torque and speeds that would be typical to motors that drive a belt driven load and with normal torque charateristics and only include standard nominal voltages for North America for the most part.
Any motor that don't fit in there pretty much would have to go by motor nameplate to establish load current rating, this would include your mentioned high speed motors and pretty much anything over 2.3 kV also.