Setting functions
8.9 Safe Torque Off (STO) safety function
Converter with control units CU250D-2
Operating Instructions, 04/2014, FW V4.7, A5E34261542B AA
239
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.
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.
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.
Commissioning STO
8.9.3.1
We strongly recommend that you commission the safety functions using a PC tool.
If you use a PC tool for commissioning, then you set the functions using the graphic screen
forms and you do not have to work with parameters. In this case, you can ignore the
parameter tables in the following sections.
Table 8- 30 PC-based commissioning tools
Can be downloaded at no
charge
STARTER STARTER
(http://support.automation.sieme
ns.com/WW/view/en/10804985/1
6SL3072-0AA00-0AG0
Startdrive Startdrive
(http://support.automation.sieme
ns.com/WW/view/en/68034568)
6SL3072-4CA02-1XG0
Commissioning the safety functions with STARTER is subsequently described.
A tutorial is available for Startdrive: Startdrive tutorial
(http://support.automation.siemens.com/WW/view/en/73598459).
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