Siemens SIMATIC ET 200pro FC-2 Operating Instructions Manual page 120

Advanced commissioning
7.7 Safe Torque Off (STO) safety function
"[...] [The converter] does not supply any energy to the motor which can generate a torque
(or for a linear motor, a force)."
The STO converter function complies with what is defined in the standard.
The distinction between Emergency Off and Emergency Stop
"Emergency Off" and "Emergency Stop" are commands that minimize different risks in the
machine or plant:
The STO function is suitable to implementing an Emergency Stop, however not an
Emergency Off.
Risk:
Measure to minimize
risk:
Command:
Classic solution:
Solution with the STO
safety function inte-
grated in the drive:
118
Risk of electric shock:
Safe switch off
Switching off the electric power sup-
ply for the installation, either com-
pletely or partially.
Emergency Off
Switch of the power supply:
STO is not suitable for safely switch-
ing of an electric voltage.
Operating Instructions, 04/2018, FW V4.7 SP10, A5E34257324B AF
Risk of unexpected motion:
Safely stop and prevent restarting
Stopping or preventing the potentially
hazardous motion.
Emergency Stop
Switch-of the drive power supply:
Select STO:
It is permissible that you switch of the
converter supply voltage as well.
However, this measure to reduce risk
is not specified.
SIMATIC ET 200pro FC-2 converter