Siemens SINAMICS G120 Operating Instructions Manual page 247

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.
Application examples for the STO function
The STO function is suitable for applications where the motor is already at a standstill or will
come to a standstill in a short, safe period of time through friction. STO does not shorten the
run-on time of machine components.
Examples
When the EMERGENCY STOP button
is pressed, it is not permissible for a sta‐
tionary motor to inadvertently acceler‐
ate.
A central EMERGENCY STOP button
must prevent the unintentional acceler‐
ation of several motors that are at a
standstill.
The distinction between EMERGENCY SWITCHING OFF and EMERGENCY STOP
EN 60204‑1 defines "EMERGENCY SWITCHING OFF" and "EMERGENCY STOP" as actions
taken in an emergency. Further, it defines various stop categories for EMERGENCY STOP.
"EMERGENCY SWITCHING OFF" and "EMERGENCY STOP" minimize different risks in the
system or machine.
Action:
Risk:
Measure to minimize
risk:
Converter with the CU250S-2 Control Units
Operating Instructions, 04/2018, FW V4.7 SP10, A5E31759476B AG
Possible solution
● Connect the EMERGENCY STOP pushbutton with a
failsafe inverter digital input.
● Select STO via the failsafe digital input.
● Evaluate the EMERGENCY STOP button in a central
control.
● Select STO via PROFIsafe.
EMERGENCY SWITCHING OFF
Electric shock
Switch off
Either completely or partially switch off
hazardous voltages.
Advanced commissioning
6.17 Safe Torque Off (STO) safety function
EMERGENCY STOP
Stop Category 0 according to
EN 60204‑1
Unexpected movement
Prevent movement
Prevent hazardous movement.
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