Re: Lifetime of CD942C20P15K is ~75 hours

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Jon Danniken" <danniken@xxxxxxxxxxx>

That's good to know, Terry, thanks for the performing that experiment. One
thing it got me wondering about concerns the failure mode of ionization at
the plate edges. Specifically, would there be half the amount of ionization
at half of the voltage?

What I'm getting at here is the possibility of using twice as many
942C10P33K caps per string (at $1.68 each) instead of the 942C20P15K units
(at $2.45 each).

Looking at 12 of our "old faithful" 942C20P15K in series yields 12.5 nF; 11
of these series cominations in parallel gives 137.5 nF at a cost of $323.00.

Looking at 24 of the 942C10P33K in series yields 13.75 nF; 10 of these
series combinations in parallel would give 137.5 nF at a cost of $403.00.

It would end up costing 25% more than the 942C20P15K caps, and there would
be twice as many of them to deal with.  If there would be a significantly
longer MTBF using twice as many of them per string, perhaps it might justify
the added expense and hassle of using twice as many.

Jon

> Original poster: Terry Fritz <vardin@xxxxxxxxxxxxxxxxxxxxxxx>
>
> Hi All,
>
> I finally did the great CD942C20P15K MMC capacitor life test.
>
> I ran three of them at 1414 VAC (60Hz) which is 2000Vpeak.
>
> http://hot-streamer.com/temp/GreatCapTest-002.jpg
>
> http://hot-streamer.com/temp/GreatCapTest-004.jpg
>
> http://hot-streamer.com/temp/GreatCapTest-001.gif
>
> The goal was to see how long the dielectric would hold up to
> ionization at the edges of the plates which is the limiter. [snip]