Signaling Circuit; Feedback Circuit; Stop Categories - Siemens SIRIUS 3SK1 Manual

Industrial controls safety engineering safety relays
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4.3.4

Signaling circuit

A current signaling path provides a safety-related output signal.
With 3SK1 relays, the signaling circuits are always implemented as NC circuits. This means
that when the safety function is triggered, or a fault is detected, the signaling circuits will
close.
With 3SK1 semiconductor devices, the signaling circuits are always implemented as NO
circuits. This means that when the safety function is triggered, or a fault is detected, the
signaling circuits will open.
4.3.5

Feedback circuit

A feedback circuit is used to monitor controlled actuators (e.g. relays or load contactors) with
positively-driven contacts or mirror contacts. The safety-related outputs can only be activated
if the feedback circuit is closed.
Note
When 3SK1 expansion units are used on 3ZY12 device connectors with 3SK1 Advanced
basic units, it is not necessary to incorporate the expansion modules in the feedback circuit
wiring. This is implemented internally via the device connector.
4.3.6

Stop categories

Stop category 0
Non-controlled shutdown by immediately switching off the power to the machine's drive
elements.
Stop category 1
Controlled stopping where the energy feed is interrupted with a time delay, or is only
interrupted once standstill has been reached.
Note
Time-delayed shutdown of safety-related outputs in accordance with Stop category 1 is not
ensured under all operating states.
In the case of some internal device faults, and when disconnecting the supply voltage, these
safety-related outputs are switched off instantaneously.
SIRIUS 3SK1 safety relays
Manual, 06/2018, A5E02526190021A/RS-AD/004
Safety systems - General information
4.3 Basic terminology
35

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