RE: Another question

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

Original poster: "Pete Komen by way of Terry Fritz <twftesla-at-qwest-dot-net>" <pkomen-at-zianet-dot-com>

Hello Chris,

If your cap is resonant or nearly so with the secondary of the HV
transformer and if the spark gap is too large, the energy put in by the HV
transformer doesn't leave the circuit.  Each half cycle adds its part to the
energy sloshing around in the resonant circuit of the XFMR secondary and the
cap.  A fixed size cap can store more energy but at higher voltage.  E = C *
V**2 / 2  (energy equals capacitance times voltage squared divided by 2.)

Resonant means that the inductor (the XFMR secondary in series with TC
primary) and the capacitor will pass energy back and forth.  Think of a
swing with speed being inductance energy and height being capacitance
energy.  At the bottom of the swing, speed is highest (the most current is
flowing and all the energy is stored in the inductor),  At each end of the
swing, speed is zero and potential energy is highest (no current is flowing
and the cap holds all the energy and is at highest voltage).  If the swing
is nudged in sync with the swinging, the swing goes farther and higher.  If
that resonance is at the line frequency (60Hz in USA, 50Hz in Europe), the
energy fed in is pushing the swing higher and higher until something gives.
With the swing analogy, at resonance the added push is always in the
direction of movement of the swing.

Thus you have the concept of LTR (Larger Than Resonant) Caps.  Sized about
50% larger than resonant size, the resonant frequency is far enough from the
line frequency to prevent the build up of energy. The pushes will keep the
swing going but it won't go higher because at least part of the time is push
is in the opposite direction of the movement of the swing.

Sharp points arc farther than smooth rounded surfaces.  Edges of aluminum
foil are very sharp.

That's my best effort at a simple explanation.  I hope it helps.

Pete Komen

-----Original Message-----
From: Tesla list [mailto:tesla-at-pupman-dot-com]
Sent: Monday, December 24, 2001 9:34 PM
To: tesla-at-pupman-dot-com
Subject: Another question

Original poster: "Chris by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<chris-at-atomic-pc-dot-com>

Hi,

Can someone explain to me, in non-EE terms, how the voltage in the TC
primary can rise so high above the power transformer's rated output?
Doesn't there have to be some extra induction taking place?  What causes
it?  3 inch lightning bolts inside the capacitor box when I'm running
"only 10 kV" are still puzzling me.  They sound like firecrackers going
off  ... though I didn't yet go out and try closer spark gap settings...

Thanks,
Chris