August 2013 Electrical Apparatus

August 2013 Electrical Apparatus

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

The Motor Primer, first presented to the Institute of Electrical and Electronics Engineers in 1999 and produced in several editions since, has come to be relied upon by many as a source of answers to questions about motor storage and installation, temperature, efficiency, bearings and lubrication, starting duty, service factor, noise, effects of voltage variation, and circuit protection.

As useful as the text has proven to be, however, it fails to answer certain questions, makes questionable recommendations, and perpetuates several misunderstandings.

The Primer‘s explanation of how induction motors work, for example, does not explain rotor construction. The text offers an inadequate explanation of random windings and factory testing. No clear definitions of “small” and “large” motors are provided. Explanations of motor acceleration are vague. The Primer‘s discussion of core loss and efficiency is imprecise, and the text’s recommendations for motor grounding are inconsistent with NEMA and the National Electrical Code.

So while the Motor Primer offers many useful insights, readers will need to look elsewhere for information about a number of subjects, including vertical high-thrust motors, belt drives, inverter usage, hazardous area requirements, starting methods, ventilation requirements, and enclosure variations.

To order a back issue with the full article, “The limitations of the Motor Primer” call 312-321-9440 or visit our online webstore.

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