Hi this is JohnBG2021. I’d like to refine my answer to this question with the following lines:
1. I agree with c_mitra , Vicor’s note I mentioned earlier on apparently shows capacitors XY safety rating, but only includes some figures for Y type, and is an application note more focussed on how to use Vicor products than to explain XY Cap ratings.
2. Found
Learn about Class-X and Class-Y capacitors, where they are used, and why they are referred to as
with more detail and accuracy about XY Cap safety ratings.
3. The so called XY safety ratings standard is just a half-way job because Voltages alone do not overheat or burn things: It’s a combination of enough Voltage and enough current, Amperes burn things.
4. In the muRata Cap specs attached to question one observes that all graphs in page 2 include a clear
DC0V.
But neither manufacturers nor IEC related standard supply DC tests, with currents, just a few orienting vague AC Voltages out of barely specified tests, and there’s a good reason:
The manufacturer doesn’t know the currents you plan to use through this capacitor, after all it’s your design, it’s your job to know whether currents flowing through your circuit are ok or not.
5. The capacitor you have inquired about is a cheap 2.2nF +-20% rated by manufactured with 250Vac(rms) meaning
this 250V is the recommended top Vdc you asked for provided you limit AC current that may flow through this capacitor, down to safe levels, safe for the capacitor to not overheat and end up with through hole.
6. Just in case
working with single phase then Vac(peak)/sqrt(2)=Vac(rms) supplied
working with 3 phase then Vac(peak)/sqrt(3)=Vac(rms) supplied
7. I found the
Vac(rms) in muRata specs confusing so I looked for same cap type value in Radio Spares and it turns out that Vishay has quite the same capacitor, but clearly stating 250Vac only, have a look:
8. muRata specs included in question shouldn’t mix AC and RMS.
V values, in this context, are either
AC amplitudes, or
DC flat really 0Hz, or
rms: equivalent DC to an AC signal would carry same power.
9. Vishay specs for equivalent cap,
again, as abridged as specs can be for mass production cheap components, but at least including:
9.1. Leakage currents graph: all caps have a parallel resistance, for
2.2nF and 500Vac I_leak expected below approx. 300uA.
9.2. Duration and DC voltage of endurance test carried out.
Tested sample :
9.2.1. Survived, held 2 seconds on 2.5kVac
9.2.2. Destroyed (stopped functioning as cap) after 60s on 1.5kVac
9.2.3. Destroyed (cap kaput and coating melted) after 60s on 2kVac
Note that in equivalent Vishay cap specs you chose, there’s no ‘Vac(rms)’ that as I said is at best confusing.
Hope it helps
JohnBG2021