# [TCML] Dv/Dt Value of Cap's

P Tuck follies at ntlworld.com
Mon Sep 8 01:49:16 MDT 2008

```Hello.
I will be using CD 942C20P-15K-F caps which are 2Kv, would the Dv/Dt value
of 2879v/uSec for these caps be exceeded if I run the primary at 235 KHz ?
I know this value relates to the rate of voltage change over time, but I am
not too sure how critical the Dv/Dt value is, and whether it is best to stay
well away from the critical figure given for the cap's in their
specification.

I *think* the formula for calculating this value is ( 2 x pi x Cap's rated
DC voltage x Freq in Khz) / 1,000,000
Which equals (2 x pi x 2000 x 235000) / 1,000,000 = 2952 uSec

The cap's specs only show 2879 for this value however, so my figure (if the
formula is correct) is slightly higher (only 2.5% admittedly). As I am using
JavaTc I can play around with the design to get a lower resonance freq'
otherwise.

I got the above formula from the archives so I am assuming it is correct, if
not can someone enlighten me.

Philip

```