Siemens SINAMICS G120C Operating Instructions Manual page 258

Advanced commissioning
8.16 Safe Torque Off (STO) safety function
Function description
Table 8-41
1. The converter identifies when STO is selected via
2. The converter interrupts the energy supply to the
3. The converter signals "STO is active" via a failsafe
Figure 8-27
(A): When selecting STO, if the motor is already stationary (zero speed), then STO prevents
the motor from starting.
(B): If the motor is still rotating (B) when STO is selected, it coasts down to standstill.
The STO safety function is standardized
The STO function is defined in IEC/EN 61800-5-2:
"[...] [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 conforms to IEC/EN 61800-5-2.
Example
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.
Application
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.
256
Principle of operation of STO
Safe Torque Off (STO)
a failsafe digital input or via PROFIsafe.
motor.
digital output or via PROFIsafe.
STO when the motor is at standstill (A), and rotating (B)
Standard converter functions linked with STO
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If you use a motor holding brake, the converter
closes the motor holding brake.
If you use a line contactor, the converter opens
the line contactor.
---
Possible solution
• Connect the EMERGENCY STOP pushbutton with a failsafe
converter digital input.
• Select STO via the failsafe digital input.
• Evaluate the EMERGENCY STOP button in a central control.
• Select STO via PROFIsafe.
Operating Instructions, 02/2023, FW V4.7 SP14, A5E34263257B AK
SINAMICS G120C Converters