Subject:  RMS
  Date:   Tue, 3 Jun 97 09:56:25 EDT
  From:   pierson-at-ggone.ENET.dec-dot-com

>Sorry guys but I think I might be missing something here. If a 
>capacitor is rated for 20,000 V RMS then it must be able to take
>a peak voltage of 28,280 V (RMS * 1.414 = PEAK). Is this not
        It is for a sine wave.
        Tesla coils tend to have LOTS of nonsinusoidal waves
        around, especially for spark gap operated ones.

>  To convert from peak voltage to rms you divide by 1.414 (or
>multiply by .707) To convert rms to peak you multiply by 1.414
>if you dont believe me just hook a o-scope to the hotwire in an 
>outlet (carefully) and you will see a peak of about 170V, that 
>satisfies the equation.      
        Yep.  Thats a nice sine wave.  (Sometimes it gets not so
        nice with a spark gap operated tesla coil attached....)

>  In a Tesla Coil circuit however, I wouldn't go near the
>max V rating. I go by the rule of thum: primary tank circuit caps
>should be rated for atleast twice the input voltage. I know all 
>about those transient voltage spikes - I have lost a few Xformers,
>and not to mention something really weird: a couple days ago I 
>fired up my small coil, after a little while when the safety gap 
>arced I saw a spark come out of an outlet on the other side of 
>my apartment.
        If the safety gap returns to 'green wire ground', the HV has
        just been switched (by the safety gap, acting as switch) onto
        the green wire ground.  Sparks can now show up almost
        anywhere.  If the safety gap is returned to 'neutral', same
        thing happens.