ANSI/NEMA MG 1-2021: Motors and Generators

An electric toothbrush that is powered by an ANSI/NEMA MG 1-2021 electric motor.

ANSI/NEMA MG 1-2021 deals with a piece of technology more ubiquitous than most people realize: electric motors.

Electric Motors Are Everywhere

The electric motor is an essential component of many products used in daily life. For example, in the common household kitchen alone, motors are found in microwave ovens, refrigerators, blenders, and even the clocks on ovens. However, as devices providing usable mechanical energy converted from electrical energy, motors can face many challenges. While most motors found in everyday appliances are highly reliable, some have been known to fail due to a variety of reasons, such as over-current, low resistance, overheating, dirt, moisture, and vibrations.

There is no method of completely ensuring that these incidents will never occur, but motors can be correctly assembled and fabricated during the manufacturing stage to reduce the possibility for failure. However, with the plentiful variety of motor types with a wide range of uses, ANSI/NEMA MG 1: Motors and Generators has long been a necessity.

What is ANSI/NEMA MG 1-2021?

ANSI/NEMA MG 1-2021: Motors and Generators is intended to assist users in the selection and application of motors and generators. This comprehensive document not only compiles general information on the different types of motors, either by their size, electrical type, application, variability of speed, or methods of cooling, but also covers specifications on electrical current and related components.

Furthermore, this standard covers testing procedures to determine the exact capabilities of fabricated motors. These are expressed through the rating of a machine, which consists of the output (or input, for machines that are designed for absorbing power) power together with any other characteristics, such as speed, voltage, and current.

Changes to ANSI/NEMA MG 1-2021

As a standard for an incredibly important yet varied product, ANSI/NEMA MG 1 has undergone many revisions, with the 2021 revision being the current edition.

In addition to corrections and editorial updates, some important changes made to ANSI/NEMA MG 1-2021 include:

  • Definition for Open Independently Ventilated Machine was revised.
  • Definition for Totally Enclosed Nonventilated Machine was added.
  • Table 4-6, which was “Maximum Eccentricity of Mounting Rabbet” in the 2018 edition of the standard, was retitled “Tolerances for the Mounting Rabbet for Type P-Base Flange Mounting Motors.”
  • Table 12-10, which was “Efficiency Levels” in the 2018 edition of the standard, was retitled “Efficiency Levels of 60 Hz Motors.”
  • Section II, Part 18, “Definite Purpose Machines,” was revised in its entirety, with updated electrical ratings for all applicable special purpose motors and manufacturing requirements for hermetic motors. Its clauses were also renumbered according to specific use motor type.
  • Revision made to Voltage Stress requirements.

Users can find a summary of changes made to ANSI/NEMA MG 1-2021 listed in in the beginning of the document along with the corresponding locations where those revisions took place. Past users of this standard who want to learn more about a supplement that was added to the 2016 edition of this standard can read Supplement to ANSI/NEMA MG 1-2016 Adds Testing Methods for Over-Air Motor Efficiency.

ANSI/NEMA MG 1-2021: Motors and Generators is available on the ANSI Webstore.

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