4.7 SOS
Definition according to EN 61800-5-2:
"This SOS function is used for safe monitor‐
ing of the standstill position of a drive."
Example of how the function can be used
Example Possible solution
A protective door must only be opened if a motor is in
the safe standstill state.
● Select SOS
● A higher-level controller brakes the axis (e.g.
position-controlled) down to standstill within
the configured time between the selection of
SOS and when it becomes active.
● Standstill is then safely monitored via the
SOS function.
The protected machine areas can be entered without having to shut down the machine as long
as SOS is active.
After SOS has been selected it becomes active after the parameterizable delay time has
expired. The drive must be braked to standstill within this delay time (e.g. by the controller).
Drive stopping is monitored using an SOS tolerance window. When this function is activated,
the current actual position is saved as a comparative position, until SOS is deselected again.
Any delay time is cleared after SOS is deselected and the drive can be immediately moved.
The drive is stopped with SS1 when the standstill tolerance window is violated.
Note
Contrary to SS1 and SS2, SOS does not automatically brake the drive
The control still enters the setpoint.
This means that in the user program of the control system, the system must respond to the
"SOS selected" bit so that the control system brings the drive to a standstill within the delay time.
Safety functions integrated in the drive
4.7 SOS
Safety Integrated (with SINAMICS S120)
Commissioning Manual, 02/2020, A5E46305916B AB 125
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