Safety considerations
49
06/10 MN03402004Z-DE/EN
Failure rates
Table 4:
Failure rates of motor-protective circuit-breaker PKE
Determining the MTTF
d
From failure rate
l
du
of the motor-protective circuit-breaker
the MTTF
d
value is determined as follows:
• MTTF
d
for 40 °C:
• MTTF
d
for 60 °C:
Interval of repeat testing (test function)
Failure rate of test function:
Failure rates
l
[FIT]
Basic unit
Trip block
Complete
device
l
su
at 40 °C
287.5
103
390.5
l
su
at 60 °C
287.5
127.4
414.9
l
sd
at 40 °C
143
30
173
l
sd
at 60 °C
143
35.6
178.6
l
du
at 40 °C
296.1
238
534.1
l
du
at 60 °C
296.1
248.6
544.7
l
dd
at 40 °C
428.4
473
901.4
l
dd
at 60 °C
428.4
491.6
920
MTTF
d
=
1
= 1.87 x 10
6
h
l
du
x 534.1 FIT
MTTF
d
=
1
= 1.84 x 10
6
h
l
du
x 544.7 FIT
l
diag
=
l
du
(CPU) +
l
du
(switch) +
l
du
(control section actuator) +
l
du
(actuator) = 350 FIT
Summary of Contents for PKE12 Series
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