Ceramic caps and high voltages

[Ekuryua]

I've been searching for a while but can't find much info about actual breakdown voltages of the typical ceramic caps that come around(class I, I believe). Anyone would have any idea?
I've read 300-400V, but that seems quite low.

Another question I had was how much does capacitance change with voltage with ceramic caps.

Thanks for any more info.

[Hewitson]

This particular brand (which I often use as they're stocked at Jaycar) are rated at 500V.

http://www.suntan.com.hk/Ceramic-Capacitors/TS15.html

[Time]

You can get ceramic capacitors well into the 40,000 volt range.  They are called 'door knob' capacitors because they look like door knobs.  Not sure if that answers your question.

[Hewitson]

These particular ones are rated for 50kVDC, don't look much like a doorknob to me though

[Ekuryua]

Thanks for pointing out some higher voltage ones:)

Any recs of where to get any of those in EU/with decent s&h fees?

[Time]

These particular ones are rated for 50kVDC, don't look much like a doorknob to me though

I seriously doubt that capacitor is rated at 50kVDC.  You can't always trust the generic picture for products on distro sites.  If you examine that picture closely it says "500V".  50kVDC is enough to breakdown the air between those leads.

I am not sure about where you can get them in EU.  The brands I am most familiar with in the 10s of kV range are TDK and Murata though.  General Atomics makes good HV capacitors with higher capacitances but they are expensive and not usually ceramic.  Capacitors of this sort are typically expensive and can't fit into the typical hobbyist budget ($50-100 USD).

[Hewitson]

I seriously doubt that capacitor is rated at 50kVDC.  You can't always trust the generic picture for products on distro sites.  If you examine that picture closely it says "500V".  50kVDC is enough to breakdown the air between those leads.

I was wondering why it looked exactly the same as a cap I recently pulled out of a 240VAC circuit!

[Zero999]

The photo says 500V  and there's a difference between the withstand voltage which only has to be for just over a µs and the working voltage which is continuous.

Attached is a paper which explains the requirements for different classes of capacitor.