Filtered DC operation with my 833A vttc...

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: Brett Miller <brmtesla2@xxxxxxxxx>

All,

I have been running my vttc with a single 833A and
rectified, filtered DC for over a week now.  I'll run
over the specs and tuning info again and will include
the specs for the rectifier:

Topload:  1.75" x 6"  John Freau classic!
Breakout point:  1.5" piece of 1/8" tungsten mounted
in a steel bolt via a hole I drilled and tapped in
order to add a set screw.  I did this back when I was
working on the GMHEICSLR cup (I used 2 pcs for the
gmheic low loss spark gap - Terry suggested tunsten).
I still have it, and it works great as a lower loss
breakout point for vttc's (and SSTC's I will soon
probably find).

Secondary:  19" winding length of 26awg on a 3.5" pvc
former
Primary:   28 turns 12awg stranded (currently tapped
at turn 28)
Feedback coil:  20 turns 23awg high temp green magnet
wire
Grid leak system:  6k at 50W in parallel with a 1.1nf
50kv Yish doorknob
Tank Cap:  2.2nf (2x 1.1nf 50kv Yish doorknobs)
Plate transformer:  Large MOT, shunts removed
Full wave rectifier:  3 x P600M rectiifer (1kv at
6amps) on each leg
Filter cap:  4uf (measured) - 4 MO caps in parallel

No heating on the rectifier...and it has lived through
quite a bit of abuse over the last 1.5 weeks or so.

Observations:
-------------------
The cone of plasma the cw drive produces seems to
present an altered load on the vttc.  At 60pps my vttc
was producing over 21" sparks with a single 833A with
the primary tapped at turn 24.  In filtered DC mode, I
got about a 4 to 5 inch cone of plasma at turn
24...but the plate was dark to cherry red, and the amp
clamp showed between 4 and 6 amps from the wall.

I then switched to turn 28, and the brush discharge
became more energetic and also about 2 more inches in
length, with occational swordlike sparks sporatically
extending further out into space.  However, the plate
ran much hotter at this setting, and the amp clamp
showed around 10-11a with peaks up to 12 amps.

After being inspired by seeing a video of one of Steve
Wards Solid state CW coils, I determined a method for
creating a breakout of pure plasma that will roam
around the toroid at will and seems to be able to
sustain itself indefinately (as long as power is
applied.  While this is going on you can also control
its length using the variac.

I'll say first that you probably wouldn't want to do
this at home if you are worried about losing
components.  I was able to do this only because I ran
without a breakout point.  Turn up the variac to
around 80 - 100 volts.  Start an arc with a grounded
rod on an insulated (long) stick.  You can then turn
the power up and watch it roam around the toroid.  If
it extinguishes, turn down the power.

Here's a clip:

www.hot-streamer.com/brett/vttc/cw/roving_plasma_cone.mov

Here is a nice manually pulled cw power arc:

www.hot-streamer.com/brett/vttc/cw/arc_pull2.jpeg

The breakout point in the above picture is the 1/8"
tungsten...most other breatkout points are quite
inefficient for cw at this power level and either
consume themselves rapidly, or simply heat up.  I have
seen the output diminish considerably in these
conditions and have found the tank cap to be still
quite cool after the run.

Here's one more:

www.hot-streamer.com/brett/vttc/cw/arc_pull3.jpeg

....you can see the Cameron (Prince) ring.  I stand by
its power.  If you are going to do something like
running a vttc with no breakout point, the ring can be
a life-saver.  I decided to show my wife the "plasma
tornado" and turned up my coil to 120v with no
breakout.  Before I had the rod in position to strike
an arc, two hot spots appeared on the feedback coil
(which was placed in the middle of the secondary.  I
immediately shut down the power.  There was no damage
beyond a couple minor carbon spots on the 6" pvc
primary/feedback former...5 seconds with sandpaper.  A
secondary to feeback coil flashover was completely
prevented by the lexan ring you see in the
"arc_pull3.jpeg" photo.  So, I must say I will be
keeping that ring on the former of this coil.

So anyone who is running a vttc and has not tried
filtered DC...it is a completely different experience.
 Highly recommended.

-Brett




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