Siemens SIRIUS 3RT Manual page 156

Configuration
6.13 Starting three-phase motors with reduced starting current peaks (contactor assembly for star-delta (wye-
delta) start)
Changing the direction of rotation from clockwise to counterclockwise
Note
In order to set the motor to counterclockwise rotation, it is not simply a case of swapping
over two phases at any location. This would result in the same conditions as those described
for clockwise rotation.
The wiring must be performed as follows in order to keep the switchover current peak which
occurs on switching from star (wye) to delta as low as possible here too:
Figure 6-9
Table 6- 10
Star contactor
I
motor
Note
If two phases are swapped over in the network in order to change the direction of rotation,
the circuit is automatically changed/reversed from the most favorable to the least favorable.
φ = switchover current factor = switchover current peak / starting current peak
The switchover current factor has a theoretical maximum value of 2
e. g. measured:
Favorable circuit: φ = 0.8
Unfavorable circuit: φ = 1.37
Note
See the main and control circuit wiring designs below; these depict the circuit diagrams for
contactor assemblies for star-delta (wye-delta) start with clockwise and counterclockwise
rotation according to the preferred wiring.
156
Correct connection of motor phases for counterclockwise motor rotation
Device sizing during normal starting
x 0.33
Line and delta contactor
I x 0.58
motor
SIRIUS - SIRIUS 3RT Contactors/Contactor assemblies
Manual, 09/2017, A5E03656507120A/RS-AE/006
Overload relay
I x 0.58
motor