I have a question about AC capacitor ratings. I've reviewed this post –
…but it only made things a little more confusing. I have a system wherein the applied mains voltage is 277Vrms/60Hz, but the EMI capacitors only have a rating of 250VAC (printed on the component and listed in the datasheet).
The caps are installed from line to ground, not daisy chained, so the full 277rms (391 peak) voltage is applied directly to each terminal of each cap. It's a power factor corrected device, switching at 40kHz, but if I understood the above linked post, that should only make the rating requirement higher, not lower.
Why don't these caps blow up immediately, or shortly after applying (what appears to be) a higher voltage than is specified? Some of these devices have been installed for years without issue.