Engineering manual - SAB 193-233-283 S A-frame (including ATEX)
008831 en 2022.02
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Technical data
6.8 Motor selection and starting torque
Motors must be sized adequately for all expected operating conditions as start-up, pull down
and load variations quite often require significantly more horsepower than nominal design.
Motor starting torque capacity must also be considered, especially when across-the-line start
is not used. Motor starting and pull-up torque must be at least 20% greater than compressor
requirements at maximum expected start-up conditions. See the torque data.
Note: Motor starting torque varies considerably from one manufacturer to another. Therefore,
make sure to obtain specific torque data for the motor used.
Unit
Starting
torque
(1)
multiplier
Breakaway
torque
(ft-lb)
Breakaway
torque
(Nm)
(2)(3)
Mass mo-
ment of iner-
tia
(lb-ft
2
)
(2)(3)
Mass mo-
ment of iner-
tia
(kg m
2
)
SAB 193 S 0.75 10 14 5.1 0.21
SAB 193 L 1.00 10 14 6.5 0.27
SAB 233 S 1.32 14 19 13 0.55
SAB 233 L 1.66 14 19 16 0.67
SAB 233 E 2.24 14 19 18 0.77
SAB 283 S 2.36 20 27 33 1.4
SAB 283 L 2.98 20 27 41 1.7
SAB 283 E 3.58 20 27 48 2.0
SAB 283 X 4.48 20 27 56 2.4
Table 23
1. High-stage or booster application.
2. Does not include coupling.
3. Inertia resolved to drive shaft.
Fig. 68: Starting torque curves, high-stage
0
25
5075100
275
250
225
200
175
150
125
19
17
15.5
14
12
10
9
[Psig]
Bar
Starting torque
Speed vs starting torque curve fully unloaded
Percentage of normal run speed
Discharge pressure
40
60
80
100
120
140
160
180
200
220
240
260
280
[Ft-lb]
Nm
54
81
108
136
163
190
217
244
271
298
325
353
380