§ 431.12 - Definitions.

§ 431.12 Definitions.

Cross Reference

Link to an amendment published at 88 FR 36150, June 1, 2023.

The following definitions apply for purposes of this subpart, and of subparts U and V of this part. Any words or terms not defined in this Section or elsewhere in this part shall be defined as provided in Section 340 of the Act.

Accreditation means recognition by an accreditation body that a laboratory is competent to test the efficiency of electric motors according to the scope and procedures given in IEEE 112–2017 Test Method B, CSA C390–10, or IEC 60034–2–1:2014 Method 2–1–1B (incorporated by reference, see § 431.15).

Accreditation body means an organization or entity that conducts and administers an accreditation system and grants accreditation.

Accreditation system means a set of requirements to be fulfilled by a testing laboratory, as well as rules of procedure and management, that are used to accredit laboratories.

Accredited laboratory means a testing laboratory to which accreditation has been granted.

Air-over electric motor means an electric motor that does not reach thermal equilibrium (i.e., thermal stability), during a rated load temperature test according to section 2 of appendix B, without the application of forced cooling by a free flow of air from an external device not mechanically connected to the motor within the motor enclosure.

Alternative efficiency determination method or AEDM means, with respect to an electric motor, a method of calculating the total power loss and average full load efficiency.

Average full load efficiency means the arithmetic mean of the full load efficiencies of a population of electric motors of duplicate design, where the full load efficiency of each motor in the population is the ratio (expressed as a percentage) of the motor's useful power output to its total power input when the motor is operated at its full rated load, rated voltage, and rated frequency.

Basic model means all units of electric motors manufactured by a single manufacturer, that are within the same equipment class, have electrical characteristics that are essentially identical, and do not have any differing physical or functional characteristics that affect energy consumption or efficiency.

Brake electric motor means a motor that contains a dedicated mechanism for speed reduction, such as a brake, either within or external to the motor enclosure

Certificate of conformity means a document that is issued by a certification program, and that gives written assurance that an electric motor complies with the energy efficiency standard applicable to that motor, as specified in § 431.25.

Certification program means a certification system that determines conformity by electric motors with the energy efficiency standards prescribed by and pursuant to the Act.

Certification system means a system, that has its own rules of procedure and management, for giving written assurance that a product, process, or service conforms to a specific standard or other specified requirements, and that is operated by an entity independent of both the party seeking the written assurance and the party providing the product, process or service.

Component set means a combination of motor parts that require the addition of more than two endshields (and their associated bearings) to create an operable motor. These parts may consist of any combination of a stator frame, wound stator, rotor, shaft, or endshields. For the purpose of this definition, the term “operable motor” means an electric motor engineered for performing in accordance with nameplate ratings.

CSA means Canadian Standards Association.

Definite purpose electric motor means any electric motor that cannot be used in most general purpose applications and is designed either:

(1) To standard ratings with standard operating characteristics or standard mechanical construction for use under service conditions other than usual, such as those specified in NEMA MG 1–2016, Paragraph 14.3, “Unusual Service Conditions,” (incorporated by reference, see § 431.15); or

(2) For use on a particular type of application.

Definite purpose motor means any electric motor that cannot be used in most general purpose applications and is designed either:

(1) To standard ratings with standard operating characteristics or standard mechanical construction for use under service conditions other than usual, such as those specified in NEMA MG 1–2016, Paragraph 14.3, “Unusual Service Conditions,” (incorporated by reference, see § 431.15); or

(2) For use on a particular type of application.

Electric motor means a machine that converts electrical power into rotational mechanical power.

Electric motor with encapsulated windings means an electric motor capable of passing the conformance test for water resistance described in NEMA MG 1–2016, Paragraph 12.62 (incorporated by reference, see § 431.15).

Electric motor with moisture resistant windings means an electric motor that is capable of passing the conformance test for moisture resistance generally described in NEMA MG 1–2016, paragraph 12.63 (incorporated by reference, see § 431.15).

Electric motor with sealed windings means an electric motor capable of passing the conformance test for water resistance described in NEMA MG 1–2016, paragraph 12.62 (incorporated by reference, see § 431.15).

Enclosed motor means an electric motor so constructed as to prevent the free exchange of air between the inside and outside of the case but not sufficiently enclosed to be termed airtight.

Equipment class means one of the combinations of an electric motor's horsepower (or standard kilowatt equivalent), number of poles, and open or enclosed construction, with respect to a category of electric motor for which § 431.25 prescribes nominal full-load efficiency standards.

Fire pump electric motor means an electric motor, including any IEC-equivalent, that meets the requirements of section 9.5 of NFPA 20 (incorporated by reference, see § 431.15).

General purpose electric motor means any electric motor that is designed in standard ratings with either:

(1) Standard operating characteristics and mechanical construction for use under usual service conditions, such as those specified in NEMA MG 1–2016, paragraph 14.2, “Usual Service Conditions,” (incorporated by reference, see § 431.15) and without restriction to a particular application or type of application; or

(2) Standard operating characteristics or standard mechanical construction for use under unusual service conditions, such as those specified in NEMA MG 1–2016, paragraph 14.3, “Unusual Service Conditions,” (incorporated by reference, see § 431.15) or for a particular type of application, and which can be used in most general purpose applications.

General purpose electric motor (subtype I) means a general purpose electric motor that:

(1) Is a single-speed, induction motor;

(2) Is rated for continuous duty (MG1) operation or for duty type S1 (IEC);

(3) Contains a squirrel-cage (MG1) or cage (IEC) rotor;

(4) Has foot-mounting that may include foot-mounting with flanges or detachable feet;

(5) Is built in accordance with NEMA T-frame dimensions or their IEC metric equivalents, including a frame size that is between two consecutive NEMA frame sizes or their IEC metric equivalents;

(6) Has performance in accordance with NEMA Design A (MG1) or B (MG1) characteristics or equivalent designs such as IEC Design N (IEC);

(7) Operates on polyphase alternating current 60-hertz sinusoidal power, and:

(i) Is rated at 230 or 460 volts (or both) including motors rated at multiple voltages that include 230 or 460 volts (or both), or

(ii) Can be operated on 230 or 460 volts (or both); and

(8) Includes, but is not limited to, explosion-proof construction.

Note 1 to definition of “General purpose electric motor (subtype I)”:

References to “MG1” above refer to NEMA Standards Publication MG 1–2016 (incorporated by reference in § 431.15). References to “IEC” above refer to IEC 60034–1, 60034–12:2016, 60050–411, and 60072–1 (incorporated by reference in § 431.15), as applicable.

General purpose electric motor (subtype II) means any general purpose electric motor that incorporates design elements of a general purpose electric motor (subtype I) but, unlike a general purpose electric motor (subtype I), is configured in one or more of the following ways:

(1) Is built in accordance with NEMA U-frame dimensions as described in NEMA MG 1–1967 (incorporated by reference, see § 431.15) or in accordance with the IEC metric equivalents, including a frame size that is between two consecutive NEMA frame sizes or their IEC metric equivalents;

(2) Has performance in accordance with NEMA Design C characteristics as described in MG1 or an equivalent IEC design(s) such as IEC Design H;

(3) Is a close-coupled pump motor;

(4) Is a footless motor;

(5) Is a vertical solid shaft normal thrust motor (as tested in a horizontal configuration) built and designed in a manner consistent with MG1;

(6) Is an eight-pole motor (900 rpm); or

(7) Is a polyphase motor with a voltage rating of not more than 600 volts, is not rated at 230 or 460 volts (or both), and cannot be operated on 230 or 460 volts (or both).

Note 2 to definition of “General purpose electric motor (subtype II)”:

With the exception of the NEMA Motor Standards MG1–1967 (incorporated by reference in § 431.15), references to “MG1” above refer to NEMA MG 1–2016 (incorporated by reference in § 431.15). References to “IEC” above refer to IEC 60034–1, 60034–12, 60050–411, and 60072–1 (incorporated by reference in § 431.15), as applicable.

IEC means the International Electrotechnical Commission.

IEC Design H motor means an electric motor that:

(1) Is an induction motor designed for use with three-phase power;

(2) Contains a cage rotor;

(3) Is capable of direct-on-line starting

(4) Has 4, 6, or 8 poles;

(5) Is rated from 0.12 kW to 160 kW at a frequency of 60 Hz; and

(6) Conforms to Sections 9.1, 9.2, and 9.3 of the IEC 60034–12:2016 (incorporated by reference, see § 431.15) specifications for starting torque, locked rotor apparent power, and starting requirements, respectively.

IEC Design HE means an electric motor that:

(1) Is an induction motor designed for use with three-phase power;

(2) Contains a cage rotor;

(3) Is capable of direct-on-line starting;

(4) Has 4, 6, or 8 poles;

(5) Is rated from 0.12 kW to 160 kW at a frequency of 60 Hz; and

(6) Conforms to section 9.1, Table 3, and Section 9.3 of the IEC 60034–12:2016 (incorporated by reference, see § 431.15) specifications for starting torque, locked rotor apparent power, and starting requirements, respectively.

IEC Design HEY means an electric motor that:

(1) Is an induction motor designed for use with three-phase power;

(2) Contains a cage rotor;

(3) Is capable of star-delta starting;

(4) Has 4, 6, or 8 poles;

(5) Is rated from 0.12 kW to 160 kW at a frequency of 60 Hz; and

(6) Conforms to section 5.7, Table 3 and Section 9.3 of the IEC 60034–12:2016 (incorporated by reference, see § 431.15) specifications for starting torque, locked rotor apparent power, and starting requirements, respectively.

IEC Design HY means an electric motor that:

(1) Is an induction motor designed for use with three-phase power;

(2) Contains a cage rotor;

(3) Is capable of star-delta starting;

(4) Has 4, 6, or 8 poles;

(5) Is rated from 0.12 kW to 160 kW at a frequency of 60 Hz; and

(6) Conforms to Section 5.7, Section 9.2 and Section 9.3 of the IEC 60034–12:2016 (incorporated by reference, see § 431.15) specifications for starting torque, locked rotor apparent power, and starting requirements, respectively.

IEC Design N motor means an electric motor that:

(1) Is an induction motor designed for use with three-phase power;

(2) Contains a cage rotor;

(3) Is capable of direct-on-line starting;

(4) Has 2, 4, 6, or 8 poles;

(5) Is rated from 0.12 kW to 1600 kW at a frequency of 60 Hz; and

(6) Conforms to Sections 6.1, 6.2, and 6.3 of the IEC 60034–12:2016 (incorporated by reference, see § 431.15) specifications for torque characteristics, locked rotor apparent power, and starting requirements, respectively. If a motor has an increased safety designation of type “e,”, the locked rotor apparent power shall be in accordance with the appropriate values specified in IEC 60079–7:2015 (incorporated by reference, see § 431.15).

IEC Design NE means an electric motor that:

(1) Is an induction motor designed for use with three-phase power;

(2) Contains a cage rotor;

(3) Is capable of direct-on-line starting;

(4) Has 2, 4, 6, or 8 poles;

(5) Is rated from 0.12 kW to 1600 kW at a frequency of 60 Hz; and

(6) Conforms to section 6.1, Table 3 and Section 6.3 of the IEC 60034–12:2016 (incorporated by reference, see § 431.15) specifications for starting torque, locked rotor apparent power, and starting requirements, respectively.

IEC Design NEY means an electric motor that:

(1) Is an induction motor designed for use with three-phase power;

(2) Contains a cage rotor;

(3) Is capable of star-delta starting;

(4) Has 2, 4, 6, or 8 poles;

(5) Is rated from 0.12 kW to 1600 kW at a frequency of 60 Hz; and

(6) Conforms to section 5.4, Table 3 and Section 6.3 of the IEC 60034–12:2016 (incorporated by reference, see § 431.15) specifications for starting torque, locked rotor apparent power, and starting requirements, respectively.

IEC Design NY means an electric motor that:

(1) Is an induction motor designed for use with three-phase power;

(2) Contains a cage rotor;

(3) Is capable of star-delta starting;

(4) Has 2, 4, 6, or 8 poles;

(5) Is rated from 0.12 kW to 1600 kW at a frequency of 60 Hz; and

(6) Conforms to Section 5.4, Section 6.2 and Section 6.3 of the IEC 60034–12:2016 (incorporated by reference, see § 431.15) specifications for starting torque, locked rotor apparent power, and starting requirements, respectively.

IEEE means the Institute of Electrical and Electronics Engineers, Inc.

Immersible electric motor means an electric motor primarily designed to operate continuously in free-air, but is also capable of temporarily withstanding complete immersion in liquid for a continuous period of no less than 30 minutes.

Inverter means an electronic device that converts an input AC or DC power into a controlled output AC or DC voltage or current. An inverter may also be called a converter.

Inverter-capable electric motor means an electric motor designed for direct online starting and is suitable for operation on an inverter without special filtering.

Inverter-only electric motor means an electric motor designed specifically for operation fed by an inverter with a temperature rise within the specified insulation thermal class or thermal limits.

Liquid-cooled electric motor means a motor that is cooled by liquid circulated using a designated cooling apparatus such that the liquid or liquid-filled conductors come into direct contact with the parts of the motor but is not submerged in a liquid during operation.

NEMA means the National Electrical Manufacturers Association.

NEMA Design A motor means a squirrel-cage motor that:

(1) Is designed to withstand full-voltage starting and developing locked-rotor torque as shown in NEMA MG 1–2016, paragraph 12.38.1 (incorporated by reference, see § 431.15);

(2) Has pull-up torque not less than the values shown in NEMA MG 1–2016, paragraph 12.40.1;

(3) Has breakdown torque not less than the values shown in NEMA MG 1–2016, paragraph 12.39.1;

(4) Has a locked-rotor current higher than the values shown in NEMA MG 1–2016, Paragraph 12.35.2 for 60 hertz and NEMA MG 1–2016, Paragraph 12.35.4 for 50 hertz; and

(5) Has a slip at rated load of less than 5 percent for motors with fewer than 10 poles.

NEMA Design B motor means a squirrel-cage motor that is:

(1) Designed to withstand full-voltage starting;

(2) Develops locked-rotor, breakdown, and pull-up torques adequate for general application as specified in Sections 12.38, 12.39 and 12.40 of NEMA MG 1–2016 (incorporated by reference, see § 431.15);

(3) Draws locked-rotor current not to exceed the values shown in Section 12.35.2 for 60 hertz and 12.35.4 for 50 hertz of NEMA MG 1–2016; and

(4) Has a slip at rated load of less than 5 percent for motors with fewer than 10 poles.

NEMA Design C motor means a squirrel-cage motor that:

(1) Is designed to withstand full-voltage starting and developing locked-rotor torque for high-torque applications up to the values shown in NEMA MG 1–2016, paragraph 12.38.2 (incorporated by reference, see § 431.15);

(2) Has pull-up torque not less than the values shown in NEMA MG 1–2016, paragraph 12.40.2;

(3) Has breakdown torque not less than the values shown in NEMA MG 1–2016, paragraph 12.39.2;

(4) Has a locked-rotor current not to exceed the values shown in NEMA MG 1–2016, paragraphs 12.35.2 for 60 hertz and 12.35.4 for 50 hertz; and

(5) Has a slip at rated load of less than 5 percent.

Nominal full-load efficiency means, with respect to an electric motor, a representative value of efficiency selected from the “nominal efficiency” column of Table 12–10, NEMA MG 1–2016, (incorporated by reference, see § 431.15), that is not greater than the average full-load efficiency of a population of motors of the same design.

Open motor means an electric motor having ventilating openings which permit passage of external cooling air over and around the windings of the machine.

Partial electric motor means an assembly of motor components necessitating the addition of no more than two endshields, including bearings, to create an electric motor capable of operation in accordance with the applicable nameplate ratings.

Rated frequency means 60 Hz and corresponds to the frequency of the electricity supplied either:

(1) Directly to the motor, in the case of electric motors capable of operating without an inverter; or

(2) To the inverter in the case on inverter-only electric motors.

Rated load (or full-load, full rated load, or rated full-load) means the rated output power of an electric motor.

Rated voltage means the input voltage of a motor or inverter used when making representations of the performance characteristics of a given electric motor and selected by the motor's manufacturer to be used for testing the motor's efficiency.

Special purpose motor means any motor, other than a general purpose motor or definite purpose motor, which has special operating characteristics or special mechanical construction, or both, designed for a particular application.

Special purpose electric motor means any electric motor, other than a general purpose motor or definite electric purpose motor, which has special operating characteristics or special mechanical construction, or both, designed for a particular application.

Specialized frame size means an electric motor frame size for which the rated output power of the motor exceeds the motor frame size limits specified for standard frame size. Specialized frame sizes have maximum diameters corresponding to the following NEMA Frame Sizes:

Motor horsepower/standard kilowatt equivalent	Maximum NEMA frame diameters
	2 Pole		4 Pole		6 Pole		8 Pole
	Enclosed	Open	Enclosed	Open	Enclosed	Open	Enclosed	Open
1/.75	48		48	48	48	48	140	140
1.5/1.1	48	48	48	48	140	140	140	140
2/1.5	48	48	48	48	140	140	180	180
3/2.2	140	48	140	140	180	180	180	180
5/3.7	140	140	140	140	180	180	210	210
7.5/5.5	180	140	180	180	210	210	210	210
10/7.5	180	180	180	180	210	210
15/11	210	180	210	210
20/15	210	210	210	210

Standard frame size means a motor frame size that aligns with the specifications in NEMA MG 1–2016, section 13.2 for open motors, and NEMA MG 1–2016, section 13.3 for enclosed motors (incorporated by reference, see § 431.15).

Submersible electric motor means an electric motor that:

(1) Is intended to operate continuously only while submerged in liquid;

(2) Is capable of operation while submerged in liquid for an indefinite period of time; and

(3) Has been sealed to prevent ingress of liquid from contacting the motor's internal parts.

Total power loss means that portion of the energy used by an electric motor not converted to rotational mechanical power, expressed in percent.

Totally enclosed non-ventilated (TENV) electric motor means an electric motor that is built in a frame-surface cooled, totally enclosed configuration that is designed and equipped to be cooled only by free convection.

[69 FR 61923, Oct. 21, 2004, as amended at 74 FR 12071, Mar. 23, 2009; 77 FR 26633, May 4, 2012; 78 FR 75993, Dec. 13, 2013; 79 FR 31009, May 29, 2014; 86 FR 21, Jan. 4, 2021; 87 FR 63654, Oct. 19, 2022; 87 FR 64689, Oct. 26, 2022; 88 FR 36150, Sept. 29, 2023]