Scope of Coverage for Small Electric Motors 

## THE SCOPE OF COVERAGE FOR THE SMALL ELECTRIC MOTORS ENERGY CONSERVATION STANDA RD S RULEMAKING
This document contains the exact definition from the statute for small electric motors , and then provides excerpts from the industry standard referenced in the statute (NEMA MG 1-1987).



## STATUTORY DEFINITION Section 340 (13)(F) of EPCA (42 U.S.C. 6311( 13)(F)) defines "small electric motor" using a dated standards publication from the National Electrical Manufacturers Association (NEMA): "(F) The term "

small electric motor" means a NEMA generalpurpose alternating current single

-speed induction motor, built in a two-digitframe number series in accordance with NEMA Standards Publication MG 1-1987. "

1Scope of Coverage for Small Electric Motors



## NEMA MG 1-1987 DEFINITI O NS Part 1 of NEMA MG 1-1987 presents definitions for various terms used in the statutory definition of "small electric motor." This section presents these relevant definitions. 

## D .1. General Purpose NEMA defines general

- purpose alternating

- current motor in section MG 1-1.05 as follows: 

### "MG 1-1.05 GENERAL-PURPOSE ALTERNATING-CURRENT MOTOR A general-purpose alternating -current motor is an induction motor, rated 200 horsepower and less, which incorporates all of the following: 1. Open construction. 2. Rated continuous duty. 3. Service factor in accordance with MG 1-12.47. 4. Class A insulation system with a temperature rise as specified in MG 1-12.42 for small motors or Class B insulation system with a temperature rise as specified in MG 1-12.43 for medium motors. It is designed in standard ratings with standard operating characteristics and mechanical construction for use under usual service conditions without restriction to a particular application or type of application." 

### As referenced in the definition of general-purpose alternating-current motor, an open machine is defined in section MG 1-1.25 by the term as follows: "MG 1-1.25 OPEN MACHINE An open machine is one having ventilating openings which permit passage of external cooling air over and around the windings of the machine
. The term `open machine,' when applied to large apparatus without qualification , designates a machine having no restriction to ventilation other than that necessitated by mechanical construction."



### 2Scope of Coverage for Small Electric Motors



### As referenced in the definition of general-purpose alternating-current motor, MG 1-12.47 states that the service factor must be in accordance with Table 12-2 shown below: Table 12-2

1.4 1.4 1.4 1.4 113 

### 1.4 1.4 1.4 1.4 110 1.4 

### 1.4 1.4 

### 1.4
... 116 

### 1.35 1.35 1.35 

### 1.35 ... 1 14 

### 1.35 1.35 1.35 1.35 ... 113 1.35 1.35 

### 1.35 1.35

.. 

### °h 125 1.25 3/4 

### 1.25 a.ax a 

### ^.r 1 X1:2 ^ 151, 1.150 1 12-125 

### 1.150 9.15'° 1.150 1.150 1.151, 

### 1S} 1.150 

### 1.150 1.150 1.154 1.150 1.150 1.154 1.150 1.150 apply only to . M is zrt



### 1.150 1.151, 1.150 .. . F3
A, B. and C =wton. 

### As referenced in the definition of general-purpose alternating-current motor, a small machine is defined in section MG 1-1.02 as follows: 

### "MG 1-1.02 SMALL (FRACTIONAL) MACHINE A small machine is either (1) a machine built in a two-digit frame number series in accordance with 11
. 01.1 or (2) a machine built in a frame smaller than that frame of a medium machine ( see MG 1-1 .03) which has a continuous, open-construction rating at 1700-1800 rpm of 1 horsepower for motors or 0.75 kilowatt for generators." As referenced in the definition of general-purpose alternating-current motor, MG 1-12.42 states that the temperature rise of small motors shall not exceed the values given in the following table: W



### IR y head wavotilazed and 1 n cooled motml, lnchtding varlaa on teo
- ecn' a sl*nce or lherttwea0up1e
............. . ......... ....... . 4. Arty " motor in a1 than the 42 rrst - a or 0

... { ^. . ......................
............................... • ^ ^y ^ , . n so-a ry The 2. The by co p . ^ i 

### 'an or the mwldm in *ny bnnbm pole tk*. w-) 1 Sail riot injure ft a ci F 1t i slaaaa 5yst- h ► d . $PWW lm AVOKWtud Ensjn int tnta4ma e.) tS^1S^dkv'.r^,nE ,j^ea.J 135



### 3Scope of Coverage for Small Electric Motors



## D.2. Single-Speed NEMA MG 1-1987 does not define the term single-speed. D.3. Induction Motor NEMA classifies and defines induction motor in section 1.15.1 as follows: "1.15.1 INDUCTION MOTOR An induction motor is an induction machine in which a primary winding on one member (usually the stator ) is connected to the power source and a polyphase secondary winding or a squirrel-cage secondary winding on the other member (usually the rotor) carries induced current. 1.15.1.1 SQUIRREL-CAGE INDUCTION MOTOR A squirrel- cage induction motor is an induction motor in which the secondary circuits (squirrel-cage winding) consists of a number of conducting bards having their extremities connected by metal rings or plates at each end. 1.15.1.2 WOUND-ROTOR INDUCTION MOTOR A wound-rotor induction motor is an induction motor in which the secondary circuit consists of a polyphase winding or coils whose terminals are either short-circuited or closed through suitable circuits." NEMA classifies and defines single-phase squirrel

- cage induction motors in section 1.17.3 as follows: 

### "1.17.3.1 SPLIT-PHASE MOTOR A split-phase motor is a single-phase induction motor equipped with an auxiliary winding displaced in magnetic position from, and connected in parallel with, the main winding. 

### Unless otherwise specified, the auxiliary circuit is assumed to be opened when the motor has attained a predetermined speed. The term "split-phase motor," used without qualification, describes a motor to be used without impedance other than that offered by the motor windings themselves, other types being separately defined. 1.17.3.2 RESISTANCE-START MOTOR A resistance

- start motor is a form of split-phase motor having a resistance connected in series with the auxiliary winding. The auxiliary circuit is opened when the motor has attained a predetermined speed. 1.17.3.3 CAPACITOR MOTOR A capacitor motor is a single-phase induction motor with a main winding arranged for direct connection to a source of power and an auxiliary winding connected in series with a capacitor
. There are three types of capacitor motors, as follows:

4Scope of Coverage for Small Electric Motors



### 1.17.3.3.1 CAPACITOR-START MOTOR A capacitor

- start motor is a capacitor motor in which the capacitor phase is in the circuit only during the starting period. 1.17.3.3.2 PERMANENT-SPLIT CAPACITOR MOTOR A permanent

- split capacitor motor is a capacitor motor having the same value of capacitance for both starting and running conditions. 1.17.3.3.3 TWO-VALUE CAPACITOR MOTOR A two-value capacitor motor is a capacitor motor using different values of effective capacitance for the starting and running conditions. 1.17.3.4 SHADED-POLE MOTOR A shaded- pole motor is a single

-phase induction motor provided with an auxiliary shortcircuited winding or windings displaced in magnetic position from the main winding." NEMA classifies and defines single-phase wound

- rotor induction motors in section 1.17.4 as follows: 

### "1.17.4.1 REPULSION MOTOR A repulsion motor is a single

-phase motor which has a stator winding arranged for connection to a source of power and a rotor winding connected to a commutator. Brushes on the commutator are short-circuited and are so placed that the magnetic axis of the rotor winding is inclined to the magnetic axis of the stator winding . This type of motor has a varying-speed characteristic. 1.17.4.2 REPULSION-START INDUCTION MOTOR A repulsion

- start induction motor is a single phase motor having the same windings as a repulsion motor, but at a predetermined speed the rotor winding is short circuited or otherwise connected to give the equivalent of a squirrel-cage winding . This type of motor starts as a repulsion motor but operates as an induction motor with constant

- speed characteristics. 1.17.4.3 REPULSION-INDUCTION MOTOR A repulsion

- induction motor is a form of repulsion motor which has a squirrel-cage winding in the rotor in addition to the repulsion motor winding . A motor of this type may have either a constant speed (see MG 1-1.30) or varying

- speed ( see MG 1-1.31) characteristic." 

## D.4. Two- Digit Frame Number Series Section 1-11.01.1 defines the system for designating frame sizes for small machines (as defined by NEMA MG 1-1987). Small machines, as defined in section MG 1-1.02, encompass all machines built in a two-digit frame number series. The two-digit frame number is defined as follows: 

### "The frame number for small machines shall be the D dimension in inches multiplied by 16"

5Scope ofCoverage for Small Electric Motors



### Section MG 1-4.01 defines the D dimension as the "centerline of shaft to bottom of feet" dimension. The equivalent IEC letter is denoted as "H". 

## NEMA MG 1-1987 STANDA RD S Later parts of NEMA MG 1-1987 include standards and rating for various motors meeting the above discussed definitions. The following section discusses these standards as they relate to scope of coverage for small electric motors. The MG-1 standards discussed in the following section are not explicitly referenced by the definitions of any of the terms listed above. 

## S.1. Ho rsep o wer Ratings Section 10.32.1 states that the horsepower and speed ratings for small induction motors, except permanent-split capacitor motors rated 1/3 horsepower and smaller and shaded-pole motors shall bel as shown in Table 10-1. Section 10.32.2 states that ratings for small permanent-split capacitor motors rated 1/3 horsepower and smaller and small shaded-pole motors shall be as shown in Table 10-2. As seen in the tables below, MG 1-1987 identifies small induction motors as motors with horsepower ratings from 1 millihorsepower up to 1 horsepower. lkbls 10.1 Harampower and Speed Ratings , Stull Induction Motors

r In NEMA MG 1-2006, the table represents "typical" horsepower and speed ratings, rather than mandating that horsepowers and speed ratings "shall be" as shown in the table.


### 6Scope of Coverage for Small Electric Motors

1 

### , !,25, 1,5, 

### 2r , 3.4 

### 5.6, a.10,12.5, 16, 20, 25 , 40 mll iliak2F tf11, tfta, 9ho, elk eis, th. and th YLS'-ni, 1.Sy 2 , ! 

### 2.3, 3, A, fix, ^, 10. 12.55 

### 16y 20. 30 , and 40 miilihci - tho. Ms

. efam, Ila. Its, fs, :i 1 V, borstpamw



## S.2. Standard Frame Sizes Part 11 of MG 1-1987 identifies three standard two-digit frame size, 42, 48, and 56.



### 7Scope of Coverage for Small Electric Motors



## S.3. Locked-Rotor Torque and Current Ratings Section 12.32.2 states that the locked-rotor torque of single-phase general-purpose small motors shall be not less than the values indicated in the table to the left below. Section 12.33.1 states that the locked-rotor current of single-phase general-purpose small motors shall not exceed the values (Design N) indicated in the table to the right below.

r 11slm-am LuLh 4-r m 

### Mot l
5pahrowu -,, Eip SSW $280

1t& 1y, try 1h V4 

### 61 ONOT& O it tzigh voltage co r *iore ed the du&9 voliBgc Mot^ 1nlrairnum locked-ro4er tdrques ups 16 lR%-kU this , dteee vr1uca m& bt e 12,33.2 Tht Locked-rover eurrenrs of atingle- _ genM-01 s shall not exceed the vAltti s lot DoN tore. sign pdWAA Star decn1 W 204W, revijad 11 -14-195 1 &Z-190. I I-124964, 1 1-214 M.



### 8Scope of Coverage for Small Electric Motors



## S.4. Breakdown Torque Ratings Section 12.32.1 states that the breakdown torque of a general-purpose single-phase small induction motor shall be higher than the figure in each torque range as given by Table 10-5. Section MG 1-10.34 states that the breakdown torque to be expected by the user for any horsepower and speed shall fall within the ranges given in Tables 10-5 and 10-6. As seen in the tables below the breakdown torques of many shaded-pole and permanent-split capacitor motors do not fall in the breakdown torque ranges of Table 10-5.



### 6NDU C& T RS, EXCEPT Table 10- t A 

### D•POL E AND PERMANENT.SP)J TCAPAaTOR MOTORS

0.35455 0.42.41.66 0.7.1.1 0M1.3 L WAS O.fs.o.7 0 66-0 65 

### ' 5` 1-1 73 1 IAS0.7-1.1 . .

SS-13 

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1 1 1 9-30 23-36 5 1 30146 3"74 46-72 13 6.11.10.4 7,2.124 8-043.5 ... 10.4.14 12.1-19, 6 13.5-2 1.5 ... 

### C ':4 13.1..19.3 . 16.€34.1 19.6.3$.9 215-314
... 

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### 9Scope of Coverage for Small Electric Motors



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### -2.1

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### 10