Johnson Controls SAB 355 - Motor;Compressor Torque

Engineering manual - SAB 355 Screw compressor unit (including ATEX)
88/156
004100 en 2020.10
Technical data
6.8 Motor/compressor torque
Ensure that the motor starting and minimum pull-up torque capabilities will exceed the compres-
sor requirements at the anticipated condition that will be experienced during normal starting.
Note: Star-delta and auto transformer (reduced voltage) motor starting methods drastically ef-
fect the starting torque available from motors as indicated:
Across-the-line
100% torque
Auto transformer
25-64% torque
Star-delta
33% torque
Fig. 65: Motor/compressor torque
Speed
25
50
75
100%
T or
que
M
otor B
Compressor
Motor A
M
otor A: Adequate to start the compressor
Motor B: Will not start the compressor