Motor Load

Tim Ganz

Member
Join Date
Dec 2010
Location
Dallas, Texas
Posts
689
Looking at prints from new equipment there is a across the line start reversing motor that is 480 volt and it's listed as 100 HP and 101 amps?

Most motor charts I have looked at list a 100 HP 3 phase motor in that size at around 123 amps.

Is there any way these prints can be correct?
 
The last couple of years I have seen premium efficiency motors with lower FLA specifications, but that seems like more of a difference than I recall. Does the motor have a some super efficiency rating?
 
If you're talking about the NEC charts than yes these will almost always show higher amps than the nameplate. The NEC numbers are a "worst case scenario" and don't reflect what those motors actually draw.

They are used to calculate wire sizes and circuit protection for feeder and branch circuits. The nameplate FLA is only used to set the overload relay. Most likely the number you're seeing on the print is the nameplate FLA, which will be considerably lower than the NEC FLA listing. I don't like putting this on a print, because a motor change-out will often render the prints inaccurate. If you're putting FLA on a print, it should clearly be identified as either NEC or Nameplate FLA, or both. That's just my opinion.
 

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