July 2013 Electrical Apparatus

July 2013 Electrical Apparatus

This is a summary of the Electrical Apparatus July 2013 featured technical article,  by Richard L. Nailen, P.E.     

Now that the National Electrical Manufacturers Association has released ANSI/NEMA MG 1-2011, the latest edition of the motor and generator standards, a close look at this document reveals some notable changes.

One significant change is the harmonization of parts of the standard with international practices. Another is the inclusion of performance data for some 50 Hz motors.

In the first section, “General Standards Applying to All Machines,” NEMA has followed the lead of Underwriters Laboratories and other U.S. organizations in harmonizing domestic standards with international practice. Section II offers new definitions of motor sizes.

In the third section, which covers large machines, some distinctions between large and small/medium motor capabilities are clarified. The fourth section applies to all a-c machines. Generators are touched on throughout MG 1.

The most sweeping change in the 2011 edition has been the addition of full-load efficiency requirements for several large groups of motor ratings not previously covered.

A clear understanding of what NEMA MG 1 does and does not say is essential for anyone intending to use the document as guidance for application, specification, and operation of any motor. Misunderstandings are all too common. Apparent omissions or contradictions should be resolved with the motor manufacturer.

To order a back issue with the full article, “NEMA Standards MG 1: what’s there . . . and not there” call 312-321-9440 or visit our online webstore.

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