Siemens Simovert Masterdrives Compendium page 58

Configuration and Connection Examples
Subsystem REACT
Parameter
Channel 1
Safety relay –K1
B10d value
nop
MTTF (-K1)
d
Channel 2
Line contactor –K2
B10d value
nop
MTTF (-K2)
d
Interim results for REACT (channels 1 and 2)
MTTF (REACT)
d
2-30
The subsystem REACT is formed by two channels. The first channel is
provided by the safety relay -K1. The line contactor provides the
second channel. Both channels are energized simultaneously by safety
switching device –A1. The positively driven NC contacts of the
contactor and relay are tested as checkback contacts every time –A1
starts.
Accumulation of faults between two consecutive actuations of the
Emergency Stop button is not detected.
♦ The structure conforms to fundamental and proven safety principles
and the requirements of Category B. Protective circuits are
provided.
♦ The safety function always remains operative when a component
fails. Component failure is detected.
This structure corresponds to Category 3 in accordance with EN ISO
13849-1:2008 /R3/.
♦ Determination of MTTF
Value
20.000.000
12 per year
16,666,666 years→
Capped to 100 years
1.333.333
12 per year
1,111,111 years →
Capped to 100 years
100 years →
High
d
Comment
Specified by manufacturer
12 actuations per year due to Emergency
Stop
B 10
d
MTTF =
d
0 1 , × n
op
Specified by manufacturer
12 actuations per year due to Emergency
Stop
B 10
d
=
MTTF
d
×
0 1 , n
op
MTTF values of both channels have been
d
capped to 100 years →
It is not necessary to symmetrize both
channels
6SE7087-6QX70 (Version AM)
Compendium Motion Control
12.2010
Siemens AG
SIMOVERT MASTERDRIVES