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电容的可靠性

For plastic film capacitors the formula
= 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.

 
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