In the United States, the National Electric Manufacturers Association (NEMA) establishes standard dimensions for electric motors. The rating plate of a motor will give a “frame size,” consisting of a number which may be followed by a letter. In purchasing a replacement motor, it is only necessary to get the same frame size to be sure of a physical fit (horsepower, voltage, type of enclosure, bearings, etc. are another matter). In the home, the most commonly encountered frame sizes are 48 and 56.
|48||2 5/8||4¼||2¾||2½||11/32 slot||1½||½|
|56||3½||4 7/8||3||2¾||11/32 slot||1 7/8||½|
The NEMA standards also describe the way the motor shaft is modified so that pulleys and gears can be securely fastened to it.
|Size||Key on shaft|
|56||3/16″ wide, 3/16″ deep, 1 3/8″ long slot|
|8,000 horsepower electric locomotive.|
Copyright © 2002 Sizes, Inc. All rights reserved.
Last revised: 3 June 2002.