Siemens SINAMICS G120D Operating Instructions Manual page 181

Figure 8-22
(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.
Further information
The operating instructions describe how to commission the STO safety function as basic
function for control via a failsafe digital input.
A description of all the safety functions is provided in the "Safety Integrated" Function Manual:
• The basic functions and the extended functions
• Controlling safety functions via PROFIsafe
Converter with the control units CU240D-2
Operating Instructions, 10/2020, FW V4.7 SP13, A5E34262100B AH
STO when the motor is at standstill (A), and rotating (B)
Overview of the manuals (Page 361)
8.12 Safe Torque Off (STO) safety function
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.
Advanced commissioning
179