X-capacitor failure modes?

Also see the video of the segmented film being shorted by arcs in action to see how shorting is localized to minimize healing required (the isolated segments connected with tiny fuse links are not shown)

so having series pair solves the problem.

Wow, that explains a lot! And, although the capacitance goes up, the voltage rating goes down. Next time you apply power, the other side of the cap is just about sure to blow!

Jon

Sounds like a ping-pong failure mechanism to me!

--
Mike Perkins 
Video Solutions Ltd 
www.videosolutions.ltd.uk

Mine sounded more like a Thompson sub machine gun. Rat-tat-tat .. rat-tat ... rat-tat-tat-tat ... Got me out of my chair prontissimo.

--
Regards, Joerg 

http://www.analogconsultants.com/

There is an other failure mode: total loss of capacity due to internal cracks. Not noticeable when used in a filter, but when used as a voltage dropper in a power supply.

"Wim Ton"

** ????

** I have seen that kind of failure and attributed it to one of the pigtail terminations going open.

If you look at how it is done, it's a wonder it ever works.

... Phil

X rated caps in plastic are designed to be self healing if possible and fail open.

"Anthony Stewart"

** This idiot just makes stuff up.

The vast majority of metallised film caps are "self healing" and class X caps typically burn out at the end of their useful life due to too much internal damage.

... Phil

Those foil capacitors can blow bits of confetti out the sides and still work fairly well afterwards. The metal is so thin that it vaporizes more than the insulator. You can call it self-healing but I wouldn't trust it to last long with the innards exposed to air.