Re: vttc

[cwillis-at-guilford.edu (by way of Terry Fritz <twftesla-at-uswest-dot-net>)]

Hey James,

This is one problem that tube coils have- they seem to give longer sparks when
the plate voltage rises very rapidly and then decays away, which is what the
doubler does.  Perhaps when you drive the coil with pulses from a level
shifter, you transfer energy to the secondary in a very short amount of time
(high peak power) due to the discharging of your level-shifter capacitor into
the oscillator.  According to one theory, the faster you can transfer energy
into the secondary circuit, the more you can get into it before breakdown in
air, and hence when breakdown occurs you get a longer spark due to higher
voltage.   When we run CW with no doubler, we can get higher average power but
perhaps a lower peak power.  The reason the doubler is necessary for long
sparks is something I really want to have explained also!

-Carl  

-at-
Sent by: "Tesla list" <tesla-at-pupman-dot-com>
10/08/2000 12:24 PM CST

To: tesla-at-pupman-dot-com
cc: 
bcc: 
Subject: vttc


Original poster: "James" <mustang3-at-home-dot-com>

Hi there coilers,
   Ok, here's my problem. My VTTC tesla with two 833a's works well. The HV
xmfr for my VTTC has a MOT with the shunts knocked out, running a 1/2 wave
voltage doubler(level shifter). Outputs about 4000 volts with 60 cycle
ripple. I bought a large xmfr with 6800 CT secondary. Using 2 uwave
rectifiers I grt 3500 volts or full-wave. This is 120 cycle ripple. The
sparks are much shorter (but sound much higher in frequency; 60/second vs
120/second). Now here it is. Why when I have so much more power with the
full-wave set up do I get a shorter spark. I have run the coil on 1/2 of the
secondary winding on AC and the sparks are much longer. To me, this is
strange. I would think that more power would give longer sparks. The MOT
xmfr gives 18 in. sparks, big xmfr gives 13 in. on AC, 10 in. on full-wave.
The full-wave is very flame like, very hot. Questions, answers?
Later,
James