Capacitor lifetime calculation?

Article from Alex McEachern) Electric Power Quality Newsletter - June 2010Sunday, June 20, 2010
Question: Capacitor lifetime calculation? (Alex Baitch)


Another old friend, Professor Alex Baitch, writes from the euphoniously-named University of Wollongong in Australia, where (at least in my experience) the single-phase line voltage can be surprisingly high...


He writes:

I was wondering whether you can help me with some investigations that I am presently undertaking. I am looking for knowledge regarding the effect of steady state voltage (or more particularly overvoltage and undervoltage) on electrical components. The body of knowledge is essentially with manufacturers as they tend to do accelerated aging testing using the technique of application of overvoltage. However, it is hard to find analytical data.

I have recently come across information from a capacitor manufacturer who provides the following relationship for metalised film capacitors: Service lifetime = (Normal voltage / Excess voltage) **9 x Service lifetime at nominal voltage. Accordingly a capacitor rated at 230V would have a life of 42% if operated at 253V instead of 230V. Intuitively sounds about right.

Assuming that a similar function applies to other types of capacitors, this has major implications for the expected service life of many devices. In particular, the present drive for energy efficient compact fluorescent lamps must have adequately rated components to ensure adequate expected life.

Are there other widely-accepted lifetime adjustments for electronic components, resulting from sustained over- or under-voltage?


Regards

Prof Alex Baitch e-mail baitch[at]besaust.com.au