Motor selection-480V 1

[irfan08]

I have a supply of 480V with +/- 10% variation. I understand the nominal voltage rating for most motors is 460V with +/- 10%. Is it a safe selection. I am just concerned with the supply if it hikes to +10% then my motor will fail.

 

[jraef]

That is by design. 480V is what is refered to as the "Distribution Voltage", 460V is referred to as the "Utilization Voltage". The reason for the difference is so that equipment, such as motors, is designed to be tolerant of voltage drops over longer distances distance from the distribution equipment. NEMA standards for motor design call for +- 10% of the equipment voltage rating, Utilities are supposed to regulate to +-2% of the distribution voltages. So if you have a 460V motor that can be fine at 506V, and a distribution system that must be maintained at no more than 504V, everything should be fine.

In theory...


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[irfan08]

but if the voltage hikes up to 528V, then we are in trouble. May be that's why there are motors with 575V name plates, but they are pricey too.

 

[davidbeach]

575V nameplated motors are for use on 600V distribution systems. 460V motors on 480V systems is the way it is done, it all works just fine.

 

[irfan08]

Just to satisfy my end user, is there a publication from NEMA to "CYA" design.

Thanks for all your help. Definitely learned alot here.

 

[starkopete]

Maybe the attached will help you "CYA".

 

[irfan08]

Great. Thanks guys.