Electrical Motor Locked Rotor Indicating Code Letters
Indicating locked rotor code letters for electrical motors
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NEMA - The National Electrical Manufacturer's Association - who sets the design standards for motors,
has established a NEMA Code letter designation to classify motors by the ratio of locked rotor KVA per
horsepower.
NEMA
Code Letter
KVA/HP
Approximate Midwith locked rotor
Range Value
A
0-3.14
1.6
B
3.15-3.55
3.3
C
3.55-3.99
3.8
D
4.0-4.49
4.3
E
4.5-4.99
4.7
F
5.0-5.59
5.3
G
5.6-6.29
5.9
H
6.3-7.09
6.7
J
7.1-7.99
7.5
K
8.0-8.99
8.5
L
9.0-9.99
9.5
M
10.0-11.19
10.6
N
11.2-12.49
11.8
P
12.5-13.99
13.2
R
14.0-15.99
15.0
S
16.0-17.99
T
18.0-19.99
U
20.0-22.39
V
22.4-and up
The starting KVA required by a motor starting at full voltage is determined from the nameplate on the
motor or from the manufacturer.
In general it is accepted that small motors requires higher starting KVA than larger motors. Standard 3
phase motors often have these locked rotor codes:






less than 1 hp: Locked Rotor Code L, 9.0-9.99 KVA
1 1/2 to 2 hp: Locked Rotor Code L or M, 9.0-11.19
3 hp : Locked Rotor Code K, 8.0-8.99
5 hp : Locked Rotor Code J, 7.1-7.99
7.5 to 10 hp : Locked Rotor Code H, 6.3-7.09
more than 15 hp : Locked Rotor Code G, 5.6-6.29
¬ How To Read a Marathon Model Number off the Nameplate
Example of Marathon Fractional Model Number: 8PE48A11O787AP R130
8
P
E
48
A
11
O
787
A
P
R130
1
2
3
4
5
6
7
10
11
12
13
Example of Marathon Integral Model Number: 2QA215TBDRA7076AL L R116
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
2 Q A
215T
B D O R A
7076
AL
L
R116
1 2 3
4
5 6 7 8 9
10
11
12
13
Date Code - Year Motor was manufactured.
Thermal Protection (not always present in every Marathon model number)
Date Code - Month Motor was manufactured.
NEMA Frame Size
Electrical Type
RPM or Speed (Fractional Motors only)
Enclosure
Frame Construction (Integral Motors only)
Style Letter indicating redesign
Sequence Number
Revision Letters (1 letter for Fractional, 2 letters for Integral)
Manufacturing Code
Modification Code (only present on nameplates of motors that have been modified through Marathon's
MOD CENTRAL)