Advanced commissioning
7.9 Safe Torque Off (STO) safety function
Converter with control units CU250D-2
Operating Instructions, 04/2015, FW V4.7.3, A5E34261542B AB
257
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 of machine components with high inertia.
Examples
Possible solution
When the Emergency Stop button is pressed, a
stationary motor should not unintentionally start.
•
Wire the Emergency Stop button to a fail-
safe input of the inverter.
•
Select STO via the fail-safe input.
A central emergency stop button must prevent the
unintentional acceleration of several motors that
are at a standstill.
•
Evaluate the Emergency Stop button in a
central control.
•
Select STO via PROFIsafe.
7.9.2
Prerequisite for STO use
In order to use the STO safety function, the machine manufacturer should have already
performed a risk assessment, e.g. in compliance with EN ISO 1050, "Safety of machinery -
Principles of risk assessment". The risk assessment must confirm that the inverter is
permitted for use in accordance with SIL 2 or PL d.
7.9.3
Commissioning STO
7.9.3.1
Commissioning tools
We strongly recommend that you commission the safety functions using a PC tool.
Table 7- 33 PC-based commissioning tools
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