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Motor nameplate letter code designations

Publication date: 
March 2009
Author: 
Tom Bishop, P.E., EASA Senior Technical Support Specialist

Motors built to National Electrical Manufacturers Association (NEMA) standards use alphabetical letter codes on the nameplate to designate a number of alternating current (AC) motor characteristics. These characteristics are the code, design, and insulation class. Read the nameplate carefully as these designations are easily misinterpreted. Similarly, re-confirm these data items when your customer provides them. For example, the letter "B" could designate a design code, insulation class or kVA code (though highly improbable.) What do these different designations mean?

Topic(s): 
Design/theory/application
Nameplates