max current of capacitor

Mmmmmmmm difficult.

Firstly the dielectric must be chosen for high frequency and low dissipation factor (low ESR).

My first thoughts would be polypropylene with maybe Teflon being a good alternative.

The dielectric losss if not constant and change with frequency, I think a good chat with someone at Wima is needed - Especially if the capacitor is used in a sensitive area or protected circuit.

Capacitors tend to explode rather spectacularly at high frequencies and currents, so if there are any perconnel safety issues definitely chat with someone technical at Wima.

Thank you for your replay.

The capacitor that I am wondering about is given in the Link a pasted above. The same cap made by evox is

http://www.evox-rifa.com/cap_catalog/pulsecap/phe450.pdf

These caps are made to work at 400 kHz. The Cap I am wondering about is the 400 Vdc .47uF cap. There is a table in the evox data sheet gives the voltage de-rating with frequency. If you extrapolate the plot on page 110 of the PDF, you get a max operating voltage of 5Vac@400kHz. this picture is for a 10 degrees rise above ambient so it tells me that if my ambient temperature is 70 degrees C then the internal heating of this cap will make the insides of the cap 80 degrees C when you have 5Vac@400kHz or 5Vac@400kHz/(1/(2*pi*400kHz*.47uF)=5.91Amps. 80 degrees C is ok for this Capacitor since it can run up to 100 degrees C. I think the power dissipated is linear with respect to temperature rise. I have heard that every 10 degrees drop in temp you can dissipate twice the current and have the same internal temperature. So this means that we should be able to run 8.35Amps (5.91*sqrt(2)) and have the internal temperature 90 degrees C (when the ambient is 70 degrees C). 90 degrees C is still ok since we can operate this cap at 100 degrees C.

This is how I'm thinking about it anyway.

What are your thoughts?

B