Efficiency of Older Motors 1

[joerob]

I am currently reviewing an application in which there are five motors ranging between 40 HP to 75 HP, 1800 rpm, 575 VAC. Does anyone have any data on what type of efficiencies can be expected of these motors. They currently operate from half to full load on the basis of ampere draw. They are approximately 40 years old. This information is tough to find.

 

[jbartos]

Suggestion: The older induction motors have somewhat lower efficiencies than the modern induction motors. There are several manufacturers providing the induction motor efficiency of your motor sizes.
Baldor Motors
Reliance
General Electric Co.
etc.
What not so obvious is that the efficiency rises slowly (similar to the square root function rise) toward their full (rated) load and then the efficiency is slowly declining.
There are many web sites dealing with motor efficiencies:

http://www.optimumus.com/motors.htm

http://www.oit.doe.gov/bestpractices/pdfs/mc-0382.pdf

http://www.greenworks.tv/business_industry/elec_motor.htm

http://www.optimumus.com/annual.htm

http://www.oit.doe.gov/bestpractices/pdfs/biblio.pdf

etc.