Re: Caps DC to AC rating

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Ed Phillips by way of Terry Fritz <twftesla-at-uswest-dot-net>" <evp-at-pacbell-dot-net>

Tesla list wrote:
> 
> Original poster: "Barton B. Anderson by way of Terry Fritz
<twftesla-at-uswest-dot-net>" <tesla123-at-pacbell-dot-net>
> 
> Hi Terry,
> 
> Seems we are "asking" for AC ratings in the various programs when we are
> concerned with DC ratings. I think we are assuming DC ratings in the calcs. I
> think the programs only require a simple label change for this particular
> input.
> 
> Bart

	This particular discussion seems to relate only to premature
insulation  breakdown due to "overvolting".  Another factor which must
(should be) be considered is that capacitors also have an AC current
rating depending on the construction and effective series resistance. 
This has been mentioned here frequently, but probably should be
restated.  The current rating is often given as a function of
frequency.  As an example, I have some 0.25 ufd mica transmitting
capacitors rated at 2500 VDC.  However, the maximum CURRENT rating at
1000 kHz is 50 amps RMS; this would correspond to an RF voltage of only
32!  "Know your capacitors before you use them!"

Ed