# Re: MMCs and cap calculations?

```Original poster: "Dr. Duncan Cadd by way of Terry Fritz <twftesla-at-uswest-dot-net>" <dunckx-at-freeuk-dot-com>

Hi Nathan!

>Original poster: "Nathan Ball by way of Terry Fritz
<twftesla-at-uswest-dot-net>" <nathan_b_ball-at-hotmail-dot-com>
>

<lots of snips>

>The caps say both 563 J and 1.6 KVDC on them, so using the equation
Wc
>(Joules) = 1/2CV^2, I get ...440uF each?
>
>I just found digikey and recalled that they were .056uF apiece, which
makes
>a LOT more sense and fits what I remembered about my capacitor.
>
>What's up? Is it me, the caps or the physics book?

I think it's cap nomenclature which has got you.  If the caps say 563J
I would bet it means 56 x 10-3 (microfarads) and J is a tolerance
figure.  Simply a question of deciphering the manufacturer's code.
First two figures (56) are the cap value, third figure ([-]3) is the
multiplier, fourth (J) is tolerance (or could be temperature
coefficient, so many parts per million per degree C; J generally means
5% tolerance or 120ppm temp coefficient).

In any case, as you calculated, 563J of energy means a cap of 440uF
and a 440uF 1,6kV cap is going to be fairly big (unless you get them
the place I got my interoscitor ;-)

Hope this helps.

Dunckx

```