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Re: Help...I'm having a lot of problems here...



Hi Kent,

I must say I am a little bit worried you may not make changes in time for the
science-fair, but I have no doubt this coil will work if the time factor
wasn't
so short. Comments below:


> Hello all...
>
> Power source:
>     Furnace transformer or NST (I'm not sure):
>             -10KVA
>             -25 milliamp

Assuming here 10kv at 25ma for 250w. Should be ok.

> Cap (set back for a good laugh):
>             -12x    2KVDC .01 uf ceramic caps soldered  in parallel for a
> total of 24KVDC
>                 -submerged in mineral oil in plexi box

Here's the problem I see. Your caps are now rated at 24kv but your capacitance
has dropped  to 0.0008uF. Your secondary/primary design is looking for
0.0184uF
using the full 5.5 turns. If this remains unchanged, your tank cap assy is
going
to require some major changes. If you stick with these ceramics, your going to
need to series/parallel a bunch of them. This will seem to require 192
caps! = 4
strings (12 caps in series) paralleled then 4 of these arrays in series.

12 caps in series = 0.0008uF at 24kv = 1 string;
4 strings in parallel = 0.0033uF at 6kv = 1 array;
4 arrays in series = 0.0134uF at 24kv.

This would get you close but you would still need to add another turn (at
least)
on the primary to tune in. Now this is the (time-factor problem I see -
getting
this done by Thursday).

Another idea is to use the 12 caps you have as arranged but with 0.0008uF
as the
capacitance. Your primary will need at least 21 turns. This might be
easier, but
your energy will be down around 0.08 joules and output voltage about 90kv.
With
the increase in capacitance as described above, your energy would be 1.33
joules
and output voltage about 360kv. Major difference. I don't know if you would
get
any output spark with the primary change but it might be possible you could
pop
off a small arc. With the cap change, you should be able to pop off some 19 or
20 inch sparks.

A note about the input power and the cap arrangements. Your input voltage at
10kv is rms. Your peak voltage seen across the cap will be 14.14kv and you
will
probably get Vp-p voltages across the cap at times which means a minimum of
28kv
rating. Usually, we derate this value by 3 for cap longevity reasons
meaning we
want a value say 80kv in this case. Of course, there are a lot who should do
this and don't, but designing under Vp-p will probably lead to a quick
failure.
It would probably be wise to run under max voltage out - and still there
are no
gaurantees the caps will last.

Everything else looked ok. Sorry for the dismal email here but this is what I
saw. Maybe some others have ideas that I haven't thought about.

Just for the heck of it, why not remove the top load and connect a piece of
wire
extending out a bit. Sharpen the end of the wire. Then connect another wire to
RF ground and sharpen the end. See how close you can get it to arc between the
two wires. Increasing inductance without the toroid will still be necessary
and
will want 15 turns (about). You may just want to quickly fassion another 10
turns to your existing 5.5 using something like #6 awg insulated wire. This
may
be the quickest way to get spark by Thursday.

Best of luck to you Kent,
Bart