Siemens SINAMICS G120 Operating Instructions Manual page 328

Advanced commissioning
6.8 Safe Torque Off (STO) safety function
The STO safety function is standardized
The STO function is defined in IEC/EN 61800-5-2:
"[...] [The inverter] does not supply any energy to the motor which can generate a torque (or
for a linear motor, a force)".
⇒ The STO inverter function conforms to IEC/EN 61800-5-2.
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 for achieving an Emergency Stop but not an Emergency Off.
Risk:
Measure to minimize
risk:
Command:
Classic solution:
Solution with the STO
safety function inte-
grated in the drive:
328
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 off the power supply:
STO is not suitable for safely switch-
ing off an electric voltage.
Operating Instructions, 01/2016, FW V4.7 SP6, A5E34259001B AC
Risk of unexpected motion:
Safely stop and safely prevent re-
starting
Stopping or preventing the dangerous
movement
Emergency Stop
Switch off the drive power supply:
Select STO:
It is permissible that you switch off
the inverter power supply as well.
However, switching off the voltage is
not required as a risk-reduction
measurement.
Converter with the CU240B-2 and CU240E-2 Control Units