=
expected value =
temperature factor =
voltage factor
is valid for
the failure rate in fit (10-9/h).
The expected value is determined for each component on the basis of long
term tests and field experience. Long term tests refer to
a minimum test period of t > 10000 h.
If such a test is carried
out at a temperature of 85°C, for example, that would,
in an appliance with a surrounding temperature of T < 40°C, correspond to an operating time of 150000 - 200000
hours; a value which comes close to real operating
conditions.
Due to the element of uncertainty about accuracy of these
calculations, a subject which has also been described in
technical literature, this value is given with a
confidence limit of 60%. However, according to our
experience, these values largely correspond to the field
results.
Correction factors which
are specific to the different applications, result from
temperature and/or voltage stress capacity according to
the following tables.
Temperature
factor
T
(°C)
40
50
70
80
100
1
2
5
10
15
Voltage factor
U/UR
0.1
0.25
0.5
0.75
1.0
0.2
0.3
1
2
5
Today
metallized plastic film capacitors with Polyester film
achieve the best values.
Here the expected value is about 2 fit. This
results in a failure rate of 10 fit.
Example: WIMA MKS
2 / 0.1 µF / 63 VDC
= 2
fit = 1 = 5 = 2 x 5 x 1 = 10 fit
The expected values for
other types of capacitors are available on request.
=
expected value
=
temperature factor
=
voltage factor
= 2 x 5 x 1 = 10 fit