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Re: Fw: Arc Impedance Study - Computer Models

Hi Barry,

At 08:54 PM 10/12/98 -0400, you wrote:
>Hi Terry,
>    The energy in the capacitor scales as the square of the voltage
>and linearly with capacitance.  The energy lost to the arc scales as
>current to the inverse 0.67 power (Attwood, Electric and magnetic
>fields, page 138).  

I don't have this book.  I don't see what is meant by "The energy lost to
the arc scales as current to the inverse 0.67 power".

>Suppose beginning values of 0.01 uF and 100 uH for
>the primary capacitance and inductance respectively.  This gives a
>primary resonant frequency of 159 kiloHertz. Suppose 20 kV on the
>primary capacitor before the gap closes.  Suppose a spark consisting
>of copper cylinders with a total gap of 0.5 inches. The energy on the
>capacitor is equal to 2 Joules.  The primary circuit surge impedance
>is 100 ohms.  The peak current when the spark gap closes is 200
>Amperes (neglecting reflected secondary surge impedance).  The peak
>power is 4 megawatts.  The peak power lost in the spark gap by Kindys'
>formula would be 3677 Watts.  This leaves 3.996 peak megawatts left
>for the secondary minus other losses.

I have not seen Kindys' formula??

>
>    Now change the capacitance to 0.1 uF and the inductance to 10 uH.
>This gives a new primary resonant frequency of 159 kiloHertz.  The
>primary circuit surge impedance is now 10 Ohms.  The energy on the
>capacitor is now 20 Joules.  The peak current when the spark gap
>closes is 2 kA.  The peak power is now 40 megawatts.  The peak power
>lost in the spark gap by Kindys' formula would be 31 kiloWatts.  This
>leaves 39.969 peak megawatts left for the secondary minus other
>losses.
>
>    The first case will quench faster than the second case.  The
>second case will loose energy in the spark gap through numerous energy
>exchanges with the secondary.  By the time the energy losses in the
>second case bring it down to the energy in the first case a lot of
>long streamers will have been created in the secondary.  The spark gap
>presents a challange.

Of course, the second coil will give longer steamers because it has 10
times the inital energy.  If you even the coil's energys by reducing the
voltage on second coil to 31.6% of the first coil (6320 volts), it will
then start out at 2 joules also.  So now they are even.  First coil is
pushing 200 amps in the primary and the second coil is pushing 632 amps in
the primary.  Since the losses in the primary circuit's wiring, capacitors
and gap generally follow the I^2R rule, the second coil may have 10 times
the loss of the first.  You would be better off with a larger primary
inductance I would think.

>
>    In 1998 such a system was demonstrated at the University of
>Maryland Physics lecture hall.  The primary consisted of 2 turns of
>2-0 welding cable wound directly around the secondary at its base (6
>inches by 27 inches, number 18 magnet wire, 5 inch by 20 inch toroid).
>The spark gap consisted of 3 gaps with 3 inch elkonite hemispheres
>about 0.2 inches separation.  They were mounted on 4 inch aluminum
>plates for heat dissipation.  The capacitance was about 0.1 uF (mica
>red RF capacitors shaped like bricks).  The primary power was about 2
>kilowatts.  The secondary spark length was about 7 to 8 feet.  The
>sparks were like nothing I have ever seen since.

If the gap, caps, and wiring were dissipating a whole bunch of heat,
perhaps a larger primary coil would have reduced the losses and deliverd
more power to the arcs given the same input power??

	Terry

>
>Barry
>
> -----Original Message-----
>From: Tesla List +ADw-tesla+AEA-pupman-dot-com+AD4-
>To: tesla+AEA-pupman-dot-com +ADw-tesla+AEA-pupman-dot-com+AD4-
>Date: Monday, October 12, 1998 1:05 AM
>Subject: Re: Fw: Arc Impedance Study - Computer Models
>
>
>+AD4-Original Poster: Terry Fritz +ADw-terryf+AEA-verinet-dot-com+AD4-
>+AD4-
>+AD4-At 01:12 AM 10/11/98 -0400, you wrote:
>+AD4APg-Hi Terry,
>+AD4APg-    Nice analysis.  There was one last problem.  What is the best
>+AD4APg-surge impedance for the primary?  This is related to the many turn
>VS
snip......