Inherent Protection - Siemens SIRIUS 3RW44 User Manual

6.7

Inherent Protection

SIRIUS 3RW44 manual
GWA 4NEB 535 2195-02 DS 06
The soft starter has integrated device protection to prevent the thyristors from
becoming thermally overloaded.
This is achieved via current measurement using converters in the three phases
and, additionally, by measuring the temperature with thermosensors at the
thyristor heatsink.
If a fixed warning threshold is exceeded, a message is generated by the soft
starter. If the fixed tripping value is exceeded, the soft starter switches off
automatically.
After a trip has occurred, a fixed 30-second pre-charge time must be observed
before the starter can be restarted.
If protection against voltage failure is active and the control supply voltage
breaks down while a trip is pending, the current trip condition of the thermal
motor model and the current pre-charge time are stored in the soft starter. When
the control supply voltage returns, the trip condition of the thermal inherent
protection before voltage failure will be restored.
In order to protect the thyristors from being destroyed by short-circuits (e. g. in
the event of cable damage or a shorted coil in the motor), SITOR semiconductor
fuses must be connected upstream. The corresponding selection tables can be
found in Chapter 10.3.7 "Branch Component Layout (Standard Circuit)" and in
Chapter 10.3.8 "Branch Component Layout (Inside Delta Circuit)".
Notice
If the soft starter is switched off via a motor protection or device protection
tripping, the action cannot be acknowledged using the "Trip reset" function until
the displayed cooling time has expired.
Device Functions
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