What is the relationship between the DC and AC ratings of capacitors?

[workinprogres]

Hello everyone, I have a few microwave caps rated at 2100 Volts AC and was wondering about their DC rating. I've heard that the DC rating of AC caps is usually 3-5 times the AC rating which seems to make sense but I'm not absolutely sure... If someone could please confirm or deny this I'd be very grateful :) Thanks in advance!

 

[dlgoff]

I wasn't sure about this thinking it wouldn't be 3-5 times the AC rating so I googled this:

This working voltage is expressed in terms of DC but the AC equivalent is about only one half of that DC rating. As the AC frequency increases the working voltage rating decreases further still.

http://www.electronics-tutorials.com/basics/working-voltage-capacitance.htm"