Siemens SIRIUS 3RW30 Manual page 28

Functions
5.1 Start modes
CAUTION
Risk of property damage
When using the 3RW30: Make sure the selected ramp time is longer than the actual motor
ramp-up time. If not, the SIRIUS 3RW30 may be damaged because the internal bypass
contacts close when the set ramp time elapses. If the motor has not finished starting up, an
AC3 current that could damage the bypass contact system will flow.
When using the 3RW40: The 3RW40 has an integrated ramp-up detection function that
prevents this operating state from occurring.
The maximum ramp time for the SIRIUS 3RW30 soft starter is 20 seconds An appropriately
dimensioned SIRIUS 3RW40 or 3RW44 soft starter should be chosen for startup processes
with a motor ramp-up time > 20 seconds.
Figure 5-1
Figure 5-2
28
Principle of the voltage ramp
Principle of the voltage ramp for the torque characteristic
SIRIUS 3RW30 / 3RW40
Manual, 01/2010, 535 1995-02 DS01