Siemens SIRIUS 3RW40, Manual

Page: 106 / 212

Commissioning
12.6 Setting the motor protection function
SIRIUS 3RW30 / 3RW40
106
Manual, 01/2010, 535 1995-02 DS01
12.6.1 Setting the electronic motor overload protection
I
e
potentiometer
The rated operational current of the motor must be set with the I
e
potentiometer according to
the mains voltage and the motor connection (wye-delta).
The current flow during motor operation is measured by measuring the current with
transformers integrated in the soft starter. This value is also used for the current limiting
function. The temperature rise in the winding is calculated based on the rated operational
current set for the motor.
CLASS potentiometer
You can set the required trip class (10, 15, or 20) with the CLASS potentiometer. A trip is
generated by the soft starter when the standardized characteristic is reached, depending on
the trip class (CLASS setting).
The trip class specifies the maximum time within which a protective device must trip from a
cold state at 7.2 x the rated operational current (motor protection to IEC 60947). The tripping
characteristics represent this time as a function of the tripping current (refer to chapter Motor
protection tripping characteristics for 3RW40 (with symmetry) [Page 161]).
You can set different CLASS characteristics according to the startup class. If the
potentiometer is set to OFF, the "electronic motor overload protection" function is deactivated.
Note
The rated data of the soft starters refers to normal starting (CLASS 10). The starters may
need to be calculated with a size allowance for heavy-duty starting (> CLASS 10). You can
only set a rated motor current that is lower than the soft starter rated current (refer to chapter
Motor current settings [Page 107]); if not, a fault will be indicated by the OVERLOAD LED
(red flashing ) and it will not be possible to start the SIRIUS 3RW soft starter.