Principle Of Sto In A Safety Function - Siemens 6SN1123-1AA00-0DA2 Configuration Manual

9 Cabinet Design and EMC
9.3 Safety of machinery – safety–related parts of controls according to EN ISO 13849–1:2008
9.3.6

Principle of STO in a safety function

SRP/CS
a
SENSE
Fig. 9-12 Principle of STO, two–channel structure
SENSE,
EVALUATE
RESPOND
9-352
SRP/CS
b
EVALUATE
A safety function essentially comprises two subsystems:
S
SENSE
S
EVALUATE
S
RESPOND
Every safety function must be configured using suitable sensors, logic units and
actuators.
The SENSE and EVALUATE subsystems are not considered in any more depth
here. The selection and installation of the components must conform to the re-
quirements of the safety function to be implemented.
DThe RESPOND subsystem in principle has a two channel structure. The first
channel includes the safety relay –K1 of the drive. This operates according to
the pulse shutdown principle with monitoring.
Line contactor –K2 forms the second channel, which is integrated in the line
infeed. The line contactor is monitored using positively–driven NC contacts.
As an alternative to integrating the line contactor, it is also possible to use a mo-
tor contactor for each motor as the second safety–related channel. The calcula-
tion results of the following application examples can be analogously applied.
SIMODRIVE 611 Configuration Manual (PJU) – 02/2012 Edition
–K2
Line contactor
Line infeed
–K1
M
Safety relay
RF
Control module
Power module
M
3
SRP/CS
c
RESPOND
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