Siemens SIRIUS 3RW30 Manual page 115

Example
● I
● xI
As soon as the selected current limiting value is reached, the motor voltage is reduced or
controlled by the soft starter to prevent the current from exceeding the limit. Since the
starting current is asymmetrical, the set current corresponds to the arithmetic mean value for
the three phases.
If the current limiting value is set to the equivalent of 100 A, the starting currents might be
approx. 80 A in L1, 120 A in L2, and 100 A in L3 (refer to chapter Starting current asymmetry
(Page 28)).
The set current limiting value must be high enough to ensure that the torque generated in the
motor is sufficient to accelerate the motor to nominal speed. Three to four times the value of
the motor's rated operational current (I
The current limiting function is always active because it is required by the intrinsic device
protection. If the current limiting potentiometer is set to clockwise stop, the starting current is
limited to the maximum possible current. We must differentiate between two cases here:
Scenario A:
3RW40 devices up to product version E06 (for 3RW40 size S0, S2, S3) or up to product
version E10 (for 3RW40 size S6 and S12)
⇒ The maximum possible limiting current is 5 times the value of the rated motor current set
on the 3RW40 soft starter (refer to chapter Setting the motor current (Page 114)).
Scenario B:
3RW40 devices from product version E07 (for 3RW40 size S0, S2, S3) or from product
version E11 (for 3RW40 size S6 and S12)
⇒ On these 3RW40 devices, the maximum possible limiting current ("max" setting) is 5 times
the value of the maximum rated operational current set on the soft starter (see the rating
plate of the soft starter). This value depends on the rated motor current actually set on the
3RW40 soft starter (potentiometer I
that can be set on the potentiometer I
Overdimensioning, due to motors with high starting current conditions, for example
For dimensioning soft starters for motors with high starting current conditions (typically I/I
8) observe the configuring information in the chapter Dimensioning of soft starters for motors
with high starting current conditions (Page 93).
SIRIUS 3RW30 / 3RW40
Manual, 10/2018, NEB535199502000/RS-AB/005
potentiometer set to 100 A
e
potentiometer set to 5 ⇒ current limiting 500 A.
e
) can be assumed as typical here.
e
). This value is identical with 5 times the maximum value
e
.
e
Commissioning
13.2 Commissioning the 3RW40
≥
e
115