Re: The Next Coil
From: Bert Hickman[SMTP:bert.hickman-at-aquila-dot-com]
Reply To: bert.hickman-at-aquila-dot-com
Sent: Sunday, August 03, 1997 8:29 AM
To: Tesla List
Subject: Re: The Next Coil
Tesla List wrote:
> From: Greg Leyh[SMTP:lod-at-pacbell-dot-net]
> Sent: Friday, August 01, 1997 5:08 PM
> To: Tesla List
> Subject: Re: The Next Coil
> Bert Hickman wrote:
> > > As part of a quickie experiment, I wanted to add C to the coil without
> > > affecting the breakout voltage of the toroid. After rooting around in
> > > the junk boxes for awhile I found a bag of big doorknob-style caps out of
> > > a laser power supply. I stacked twenty of these capacitors, each one
> > > rated at 2200pF -at-30kV, using threaded 3" standoffs between them. The
> > > finished stack, which measured about 10' in length, was then placed inside
> > > of the secondary along the center axis.
> > > Each cap had a 10Mohm stick resistor in parallel.
> > > -GL
> > Greg,
> > EXCELLENT! This is the first hard evidence that streamer propagation for
> > HF AC discharges is significantly enhanced by providing a low impedance
> > source of "instant" charge from a lumped C and not a "higher impedance"
> > distributed C! Although large toroids have seemingly "worked" better for
> > most coils, even though they may reduce peak output voltage, until now
> > there was only hand waving arguments as to possible causes.
> > Greg, you also made one heck of a nice voltage divider - by any chance
> > did you happen to measure the resulting voltage across the bottom-most
> > cap? With this, and the other known input parameters, you'd know your
> > coil efficiency (perhaps helping to resolves some earlier/animated
> > discussions of coupling, output voltages, and efficiencies!)
> Whoops! No, I did not. Wouldn't the divider drag the voltage down by a
> considerable amount, anyway? At least I know that the voltage is less
> than 600kV...
However, you've compensated for this by increasing the primary circuit's
energy. Even if the secondary voltage did get reduced, the spark output
increased by 5', and you know what the actual secondary
toriod:coil:divider capacitance is from the new operating frequency.
It's not clear that there was any practical consequence of voltage drag
down in this case, since you got significantly improved sparklength.
Perhaps even more interesting, if you indeed are getting microsecond
current spiking off the top during streamer propagation, this should
also be reflected at the bottom of your divider chain. If these are
occuring, you should be able to measure them, and also be able to derive
total streamer current. These current spikes, which should occur as
streamers explosively extend their length, should be very evident in the
divider chain current. BTW, putting the divider chain INSIDE the coil
was a great idea!
Safe magacoilin' to you, Greg!
-- Bert --