ENGINEERING MANUAL OF AUTOMATIC CONTROL
GENERAL ENGINEERING DATA
486
Motors have two current ratings locked rotor (LRA) and full
load (FLA). Locked rotor current is drawn at the instant power
is applied and before the motor starts rotating. It is also drawn
if the motor is stalled. Full load current is drawn when the motor
is running at its full load rating.
Tables 24, 25, and 26 are provided as a convenience to the
reader for reference only. In all cases the National Electrical
code and local codes take precedence.
Code
Letter
Kilovolt-Amperes (KVA) per Horsepower
with Locked Rotor
A0through 3.14
B 3.15 through 3.54
C 3.55 through 3.99
D 4.0 through 4.49
E 4.5 through 4.99
F 5.0 through 5.59
G 5.6 through 6.29
H 6.3 through 7.09
J 7.1 through 7.99
K 8.0 through 8.99
L 9.0 through 9.99
M 10.0 through 11.19
N 11.2 through 12.49
P 12.5 through 13.99
R 14.0 through 15.99
S 16.0 through 17.99
T 18.0 through 19.99
U 20.0 through 22.39
V 22.4 and up
Table 24. Locked Rotor Indicating Code Letters.
Table 25. Motor Current Ratings.
Cross -
Types TF, Types TFN,
Approximate dc Resistance
at 167F (75C)
section
TW, THW Types RHW, RHH THWN, THHN Copper
Wire
Size
AWG
of copper
Circular
Mills
Approx-
imate
Dia. in.
Approx-
imate
Area in
2
Approx-
imate
Dia. in.
2
Approx-
imate
Area n.
2
Approx-
imate
Dia. in.
Approx-
imate
Area in
2
Uncoated
Ohm/Mft
Coated
Ohm/Mft
Aluminum
Ohm/Mft
18
16
14
1620
2580
4110
0.106
0.118
0.131
0.0088
0.0109
0.0135
0.146
0.158
0.204
0.0167
0.0196
0.0327
0.089
0.100
0.105
0.0062
0.0079
0.0087
7.95
4.89
3.14
8.45
5.29
3.26
13.1
8.21
5.17
12
10
8
6530
10,380
16,510
0.148
0.168
0.245
0.0172
0.0222
0.0471
0.221
0.242
0.328
0.0384
0.0460
0.0845
0.122
0.153
0.218
0.0117
0.0184
0.0373
1.98
1.24
0.778
2.05
1.29
0.809
3.25
2.04
1.28
6
4
3
26,240
41,740
52,620
0.323
0.372
0.401
0.0819
0.1087
0.1263
0.397
0.452
0.481
0.1238
0.1605
0.1817
0.257
0.328
0.356
0.0519
0.0845
0.0995
0.491
0.308
0.245
0.510
0.321
0.254
0.808
0.508
0.403
2
1
1/0
66,360
83,690
105,600
0.433
0.508
0.549
0.1473
0.2027
0.2367
0.513
0.588
0.629
0.2067
0.2715
0.3107
0.388
0.450
0.491
0.1182
0.1590
0.1893
0.194
0.154
0.122
0.201
0.160
0.127
0.319
0.253
0.201
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