Chapter 15 Safe Torque Off FunctionME300
15-5
15-4 Failure Rate of the Drive Safety Function
Refer to Table 3 for the relevant safe loop parameters.
Item Definition Standard Performance
SFF Safe failure fraction IEC61508
S1–DCM = 88.35%
S2–DCM = 88.2%
HFT (Type A subsystem) Hardware fault tolerance IEC61508 1
SIL Safety integrity level
IEC61508 SIL 2
IEC62061 SILCL 2
PFH
Average frequency of
dangerous failure [h-1]
IEC61508
1.36 x 10
-9
PFD
av
Probability of dangerous failure
on demand
IEC61508
5.99 x 10
-6
PTI Proof test interval IEC61508 1 year
Category Category ISO13849-1 Category 3
PL Performance level ISO13849-1 d
MTTF
d
Mean time to dangerous failure
ISO13849-1 High
DC Diagnostic coverage ISO13849-1 Low
Table 3: Relevant safe loop parameters
15-5 Reset the Parameter Settings
Use Pr.06-44 to specify the reset method when an STO alarm occurs.
STO Latch Selection
Default: 0
Settings 0: STO Latch
1: STO no Latch
Pr.06-44 = 0: STO Alarm Latch. After you clear the cause of the STO Alarm, use a Reset command
to clear the STO Alarm.
Pr.06-44 = 1: STO Alarm no Latch. After you clear the cause of the STO Alarm, the STO Alarm
clears automatically.
All of the STL1–STL3 errors are “Alarm Latch” mode (in STL1–STL3 mode, the Pr.06-44 function
is not effective).
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