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2 Engineering
2.8 Safe Torque Off (STO)
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Rapid Link 5 · RAMO5 · RASP5 05/20 MN034004EN www.eaton.com
If an unintended restart is to be reliably prevented using the STO function,
this can be implemented by providing an external circuit for the STO inputs.
For example, an upstream safety relay can be used that only releases the vol-
tage for the STO inputs via a manually initiated reset function. According to
the requirements (e.g. PL r in line with ISO13849-1) for all safety functions
(e.g. EMERGENCY STOP), all components of the safety function (input/logic/
output) must be selected. The safety relay must be selected and the wiring
connected correspondingly.
The STO function implements a partial safety function via the output and
makes the use of electromechanical contactors with self-monitoring auxiliary
contacts superfluous.
Parameter bit P2-24 (start mode) is not suitable for preventing a restart in
safety-related applications.
There are two situations that result in a restart:
Manual mode
After an STO has been triggered, the drive does not restart unless a manual
reset has been performed using a switch on the device (key switch).
The prerequisite for this is that parameter bit P2-24 for configuring start-up
behavior is set to the default setting.
Automatic mode
After an STO has been triggered, the drive starts again as soon as the STO is
supplied with 24 V and the RUN command is still being transmitted via the
bus. The setting of parameter bit P2-24 is not relevant in this case.
2.8.3 TÜV certification
RASP5 speed controllers with STO function that have a TÜV logo on the
nameplate include an STO function in accordance with the standards listed
here:
This safety function corresponds to uncontrolled shutdown as defined in
IEC60204-1, Stop category 0.
Standard Classification
EN 61800-5-2:2017 SIL 3: “ Safe torque off”
EN ISO 13849-1:2015 PL e
EN 62061:2015 SIL CL 3
EN 61508, Part 1 + 2, 4 - 7: 2010 SIL 3
￫
The following information and descriptions for the STO function
are translations of the original description in English (TÜV speci-
fication).