Application document for functional safety STO, SS1 (ISO 13849-1)
Compact User Manual, 09/2016, A5E34871844AM
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When selecting the safety function (actuating the Emergency Stop pushbutton), the
instantaneous NO contacts are immediately opened in the 3SK1122-2CB41 safety relay. As
a consequence, the E-Stop function is initiated at the SINAMICS DCM. The SINAMICS DCM
reduces the armature current, inhibits the firing pulses and opens the armature contactor.
The "E-Stop active" signal must be integrated in the feedback circuit of the safety relay via a
coupling relay at digital output DO3 (X177.22).
At the same time when the NO contacts of the safety relay open, the safety-related output
expansion 3SK1211-2BB40 is shut down via the internal communication of the 3SK safety
relay; as a consequence, the safety-related coupling relays to control the armature and field
circuits are opened.
The motor current therefore goes to zero and in turn, the motor torque also goes to zero.
The motor coasts down.
In the circuit examples, the energy feed to the field power units as well as to the armature
circuit is interrupted. Controlling the field contactor is optional. However, in this case, the
motor cannot be considered to be in a no-voltage condition.
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