Siemens SIMOCODE pro Operating Manual page 87

Safety guidelines
Note
It is recommended that the QE1 and QE2 contactor controls are wired to the relay outputs of
the basic unit. You need at least 1 digital module for this control function.
Note
Spurious tripping can occur if you use the internal ground-fault detection for star-delta
connections. During delta operation, the summation current is non-zero due to harmonics.
Note
If the current measuring module is switched to delta (normal case), a current which is 1/√3
times smaller must be set for the star-delta starter control function.
Example: I
I = I
s
I = 100 A x 1/√3 = 57.7 A
s
Current to be set 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 line voltage plus
motor EMF might result in a very high delta starting current if the change-over pause is too
short. The motor EMF decreases if the pause is longer.
SIMOCODE pro - Parameterize
Operating Manual, 04/2017, A5E40507630002A/RS-AA/001
= 100 A
n
x 1/√3
n
= 57.7 A
s
Parameters
4.2 Motor control
87