Siemens SIMOCODE pro System Manual page 212

Motor control
Safety guidelines
Note
It is recommended to wire the QE1 and QE2 contactor controls to the relay
outputs of the basic unit. You need at least 1 digital module for this control
function.
Notice
If you use internal earth-fault detection for star-delta circuits, this can lead to
false trippings. During delta operation, the summation current is non-zero
due to harmonics.
Notice
If the current measuring module is switched to delta (normal case), a
current which is 1/
starter control function.
Example: I
Change-over pause
The switching time from star to delta can be extended by the change-over
pause.
Reason: For motors with a high ratio between starting current and rated
current, the mains voltage plus motor EMF might lead to a very high delta
starting current if the change-over pause is too short. The motor EMF
decreases if the pause is longer.
4-34
3
smaller than normal must be set for the star-delta
= 100 A I = I
n s
I = 100 A x 1/
s
Current to be set I
3
x 1/
n
3
= 57.7 A
= 57.7 A
s
GWA 4NEB 631 6050-22 DS 03
SIMOCODE pro