Siemens Sinamics S120 Function Manual page 458

Safety Integrated basic functions
9.2 General information
Two-channel monitoring structure
All the main hardware and software functions for Safety Integrated are implemented in two
independent monitoring channels (e.g. switch-off signal paths, data management, data
comparison).
The two drive monitoring channels are implemented using the following components:
● Control Unit
● The Motor Module/Power Module belonging to a drive.
The monitoring functions in each monitoring channel work on the principle that a defined
status must prevail before each action is carried out and a specific acknowledgement must
be made after each action.
If these expectations of a monitoring channel are not fulfilled, the drive coasts to a standstill
(two-channel) and an appropriate message is output.
Switch-off signal paths
Two independent switch-off signal paths are available. All switch-off signal paths are low-
active, thereby ensuring that the system is always switched to a safe state if a component
fails or in the event of an open circuit.
If a fault is discovered in the switch-off signal paths, the "Safe Torque Off" function is
activated and a system restart inhibited.
Monitoring cycle
The safety-relevant drive functions are executed cyclically in the monitoring clock cycle.
The safety monitoring clock cycle lasts a minimum of 4 ms. Increasing the current controller
cycle (p0115) also increases the safety monitoring clock cycle.
Data cross-check
A cyclic cross-check of the safety-related data in the two monitoring channels is carried out.
If any data are inconsistent, a stop response is triggered with any Safety function.
Overview of parameters (see SINAMICS S120/S150 List Manual)
● r9780 SI Monitoring clock cycle (Control Unit)
● r9880 SI Monitoring clock cycle (Motor Module)
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Function Manual, (FH1), 01/2012, 6SL3097-4AB00-0BP2
Drive functions