Electric motors tip: What is 'guaranteed efficiency'?

Now that many more of us are looking at motor nameplate data, with emphasis on finding out what the efficiency is, what the heck is "Guaranteed Efficiency"?
 
Guaranteed minimum is another efficiency that is sometimes noted on a nameplate. This value is determined from a mathematical relationship that assumes the worst efficiency of any motor in a batch – used to determine the average (nominal) value – could have losses as much as 20 percent higher than the average. As a result, each nominal efficiency value would have a corresponding minimum efficiency value. You can view these values in Table 12-8 in NEMA MG-1.
 
Remember, when working with PdMA's Energy Cost Analysis program not to confuse this with the Full Load Efficiency.  You want to use Full Load Efficiency in the program for your analysis.

For more information on electric motor maintenance and applications, visit www.pdma.com.