[R-390] C553

[Charles Steinmetz]

David wrote:

>a while ago I researched 1kV film/foil .01's stocked at Mouser.  At 
>the present time, they have exactly one honest-to-god film-foil at 
>1kV or up:  CDE  715P103516LD3 1.6KV $4.04
>The Kemet PHE448 series is also true film/foil but they're out and 
>not ordering.
>
>Everything else is either 630V or less, or contains metalized film.

Honestly, I see no need for a rating > 600v if you use a quality 
film-and-foil.  I have never observed a failure (or even heard of 
one) of a 600v Orange Drop 225P or 715P in the C553 position (or even 
a 400v 225P or 715P, which many folks use).  I've personally 
installed well over 100 of them, and lots of other people use them, 
so there is a large information base.

>or settle for metalized and run up the voltage to reduce the odds of 
>a self-heal event.

Unfortunately, testing I did some years ago does not support the 
proposition that self-healing events in metallized film caps go down 
as the voltage rating increases, once the circuit voltage is greater 
than about 200v.  I suspect the catastrophic failure rate does go 
down with increasing voltage rating, but the self-healing kills 
filters and it does not seem to.  (Note that manufacturers do not 
consider self-healing events to be faults or failures -- they are 
part of the normal operation of metallized film caps.)

Best regards,

Charles