Scope of Coverage for Small Electric Motors

THE SCOPE OF COVERAGE FOR THE

SMALL ELECTRIC MOTORS

ENERGY CONSERVATION STANDA RDS 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 general purpose alternating

current single-speed induction motor, built in a two-digitframe number series in

accordance with NEMA Standards Publication MG 1-1987. "

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 EERE-2007-BT-STD-0007 COMMENT 03.3
Scope of Coverage for Small Electric Motors

NEMA MG 1-1987 DEFINITIONS

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."

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 EERE-2007-BT-STD-0007 COMMENT 03.3
Scope 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 ...

114 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 byco

p

. ^

bnnbm pole tk*. w-) 1 Sail riot injure ft i 'an or the mwldm in *ny

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

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 EERE-2007-BT-STD-0007 COMMENT 03.3
Scope 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:

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 EERE-2007-BT-STD-0007 COMMENT 03.3
Scope 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 ofthis 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"

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 EERE-2007-BT-STD-0007 COMMENT 03.3
Scope 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 STANDARDS

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. Horsepower 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.

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 EERE-2007-BT-STD-0007 COMMENT 03.3
Scope of Coverage for Small Electric Motors

1 , !,25, 1,5, 2r , 3.4

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elk eis, th. and t

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S.2. Standard Frame Sizes

Part 11 of MG 1-1987 identifies three standard two-digit frame size, 42, 48, and 56.

7

 EERE-2007-BT-STD-0007 COMMENT 03.3
Scope 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

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1y,

try

1h

V4

61

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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 Dosign N tore.

pdWAA Star decn1 W 204W, revijad 11 -14-1951 &Z-190.

II-124964, 1 1-214M.

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 EERE-2007-BT-STD-0007 COMMENT 03.3
Scope 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•POLE AND PERMANENT.SP)JTCAPAaTOR MOTORS

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9

 EERE-2007-BT-STD-0007 COMMENT 03.3
Scope of Coverage for Small Electric Motors

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 EERE-2007-BT-STD-0007 COMMENT 03.3