Re: VA and stored energy in capacitors

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Jolyon Vater Cox by way of Terry Fritz <twftesla-at-qwest-dot-net>" <jolyon-at-vatercox.freeserve.co.uk>

What I mean to say is at say, a voltage of 15kV, a 1nF cap stores 0.1125
Joules of
energy (E) and if the frequency (F) of the AC supply is 60Hz the reactive
power of the
capacitor is 84.8 VA under non-sparking conditions.

However there is a spark gap and when it fires E is dumped into a tuned
circuit whose
F is higher than 60Hz, say 1MHZ. The formula for reactive power VA=4(pi)FE
still
applies and E is still 0.1125Joules but F is now 1000000Hertz so the
reactive power
should  now be 1413716.7 VA (approx 1.4MVA) instead of  84.8VA which applied
when the AC frequency was 60 Hertz.

Does this agree with real-life experience- well, what this says is that with
a voltage of
15kV and a frequency 1MHz the reactive power "consumed" by a 1nF capacitor
is
1.4MVA. This seems like a large figure, but in a spark-gap Tesla Coil the
capacitor
discharges much more quickly than it charges and since power =energy/time,
discharging the same amount of energy but in much shorter time period should
only
be expected to result in an enormous increase in power.

Is this approach to calculating peak power in a TC valid? Is it a new idea
or has it
been tried before? Or is it simply incorrect?
----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Friday, May 31, 2002 12:26 AM
Subject: Re: VA and stored energy in capacitors


> Original poster: "Dave Larkin by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<teslaman15-at-hotmail-dot-com>
>
> >Since relationship between apparent power (VA), frequency (F) and stored
> >energy
> >(E) in a capacitor in an AC circuit is VA=4pFE, where it is assumed that
F
> >is
> >the line frequency (50 to 60 Hz) during the period when the capacitor is
> >being
> >charged by the transformer prior to the firing of the spark-gap, doesn't
> >the
> >same equation apply when the gap fires when F becomes the resonant
> >frequency of
> >the Tesla coil primary?
>
> Yes.  However, remember that as the spark gap fires and F increases, A
also
> increases to match it, so the energy in the capacitor remains constant.
>
> >Does this not go some way into accounting for high peak powers observed
in
> >TC
> >discharges?
>
> I can't see how.  Personally I attribute the high peak powers to a large
> current at a high voltage, although rumour has it aliens, the ghost of
> Nikola Tesla and/or Tim Bearden may be involved...
>
> -Dave-
>
>
>
>