Safe Torque Off (Sto) Safety Function; Function Description - Siemens SINAMICS G120 Operating Instructions Manual
Low voltage inverters
built-in units with cu250s-2 control units and
encoder evaluation
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Also See for SINAMICS G120:
- List manual (1256 pages) ,
- Manual (732 pages) ,
- Operating instructions manual (550 pages)
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Advanced commissioning
6.17 Safe Torque Off (STO) safety function
6.17
Safe Torque Off (STO) safety function
The operating instructions describe how to commission the STO safety function as basic
function for control via a fail-safe 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
6.17.1
Function description
What is the effect of the STO safety function?
The inverter with active STO function prevents energy supply to the motor. The motor can no
longer generate torque on the motor shaft.
Consequently, the STO function prevents the starting of an electrically-driven machine
component.
Table 6-37
1. The inverter identifies when STO is selected via
2. The inverter prevents the energy supply to the
3. The inverter signals "STO is active" via a failsafe
Figure 6-27
(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.
244
Overview of the manuals (Page 519)
The STO principle of operation as overview
Safe Torque Off (STO)
a failsafe input or via PROFIsafe.
motor.
digital output or via PROFIsafe.
Functionality of STO when the motor is at standstill (A) and rotating (B)
Standard inverter functions linked with STO
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If you use a motor holding brake, the inverter
closes the motor holding brake.
If you use a line contactor, the inverter opens the
line contactor.
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Converter with the CU250S-2 Control Units
Operating Instructions, 04/2018, FW V4.7 SP10, A5E31759476B AG
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