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Re: Fw: Arc Impedance Study - Computer Models
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). 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.
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.
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.
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
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