Siemens SIRIUS 3SK1 Equipment Manual page 177

Function of the cascading input (INK terminal)
• Safe combination of safety relays
In this application, a higher-level safety relay switches off the 3SK1 safety relay via the
cascading input via a safe output.
Example:
an EMERGENCY STOP circuit is to deactivate the entire installation as a higher-level circuit.
Several function groups (e.g., protective doors) that disconnect locally can be operated as
subordinate units.
• Additional safety sensor circuit
The INK cascading input is ANDed with sensor inputs IN1, IN2 .
PL c in accordance with ISO 13849-1, or SIL1 in accordance with IEC 62061 can be achieved
if the cascading input is wired with single-channel (positive opening) safety sensors (supply
via A1 / +24 V (identical potential to A1) and if the connecting cable is laid in a protected
fashion. The start function for the cascading input INK corresponds to the start response of
sensor inputs IN1 and IN2 (autostart or monitored start).
The cascading input INK can be controlled with floating or solid-state contact blocks
(switching to P potential). Floating contact blocks must be connected between A1 / +24 V
(identical potential to A1) and the cascading input.
• Normal switching duty
The INK cascading input can also be used for normal switching duty (not safe). The INK
cascading input can be controlled in this case with floating contact blocks or with solid-state
contact blocks (switching to P potential).
Floating contact blocks must be connected between A1 / +24 V and INK .
It is important to note that the start function of cascading input INK corresponds to the start
function of sensor inputs IN1, IN2 .
SIRIUS 3SK1 Safety Relays and 3RQ1 Positively-Driven Coupling Relays
Equipment Manual, 05/2021, A5E02526190021A/RS-AE/005
WARNING
Application / safety relay safety level
The safety level PL/SIL of the application corresponds to the lowest safety level of a
subsystem of the application when errors are excluded (protected wiring of the control
cable).
Configuration / operation
9.2 Explanation of the device's functions
177