Re: How could a pulse cap operate in TC?

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: father dest <dest@xxxxxxxxxxx>

Tl> Original poster: Steve Conner <steve@xxxxxxxxxxxx>

>>ok - i agree that Irms chart is choosed misfortuned - here are others:
>>
>>Urms (F) http://cis.ru/~dest/3.GIF
>>Irms  (F) http://cis.ru/~dest/4.GIF
>>
>>there shouldn`t be any problems with breakdown after 100 khz (1000 v cap),
>>nevertheless the currnet increases, though rather slowly.

Tl> OK. That increasing RMS current rating definitely proves that
Tl> dielectric losses _are_ significant. If they weren't, the current
Tl> rating would be constant after the "knee". I was wrong :-/

you`re right, but only if:

Tl> voltage derating vs. frequency" curve is flat up to a certain
Tl> frequency and then falls off at 6dB/oct

and if range of working frequencies is to the right from the "knee".
but in case above the curve falls off at less than 6 db/oct - just
like these charts that i saw (in most cases) in the plant`s catalogue,
that i`ve mentioned last time.

let`s discuss your viewpoint, where you told:

Tl> Typically the curve is flat up to a certain frequency and then falls off at
Tl> 6dB/oct This implies that dielectric losses are insignificant and
Tl> the limiting factor is the RMS current

ok - lets assume there is no dielectric loses at the working
frequencies - no loses at all.
so what - it couldn`t be that a cap is so good (small ESR), that curve is
flat up to 350 khz? but then at 100khz (my coil frequency) the current
must be 3.5 times smaller, than Terry measured. in such case my words:

>it`s useless to write rms rating without its frequency!

are not so senseless, aren`t they? coz _before_ this frequency maximum
Irms is limited too, but not by active losses. and the voltage at this
Irms is not equal to DC limit of the cap - it`s AC limit, but AC limit
again _on the given frequency_ - coz AC limit it`s a function, but not
the constant, as "maximum Irms".