[TCML] For the SISG experienced out there

[bartb]

Hi Phil,

Thanks for the great advice. For DC charging in the past, I also used a 
series of diodes, but thought I would just go the route of some hv 
diodes to keep construction easy. I'll be using 15kV diodes, but it 
sounds like it might be wise to double up and series 2 per bridge leg.

Unless I do a voltage doubler or something, the 6 boards sounds like out 
of the question for the NST. So, the topology for firing a series of 
boards is per the 300V Sidac's at 3600V per board, so 3600V x 6 boards = 
21.6 kV. It looks like for the 11 kV NST = 4 boards. Now, if I use my 
14.4kV pig, a little over 5 boards. Maybe, I should just settle on 5 to 
make it easy and keep 1 board as a spare.

Are there any coil specific issues? For example, can I use a standard 
8.5" x 40" coil with 9"x30" spun toroid? This coil is a bit lossy (wound 
with 24 awg at 1790 turns). Are there any preferences for cap sizes? If 
I use the pig, I'll likely go with my 60kV pulse caps at 0.06uF tank size.

My original plan (bought the 6 pcbs from Mark about a year ago) was to 
use 4 boards for an sisg coil and 2 boards to power my attempt at 
Tesla's flat coil at 1/2 scale. That coil is mostly done and maybe I 
should stick to that plan. If I use the 4 boards, I planned on the NST 
mentioned with my smaller 4.5"D coil. As you can see, I'm totally unsure 
if I should use existing coils or wind a new coil altogether for the 
sisg. So, if there are some "coil LC preferences", then that would 
likely dictate a new coil.

Oh, the NST was a 12/60, after removing some windings and shunts, 11/200 
(nothing special, but it sure can dance).

Take care,
Bart

FIFTYGUY at aol.com wrote:
>  
>  
> In a message dated 5/7/08 10:32:31 P.M. Eastern Daylight Time,  
> bartb at classictesla.com writes:
>
>  
>   
>> Question: Has anyone ran an NST type transformer (shunts minimized)  into 
>>     
>
>   
>> an SISG setup (or beyond)? 
>>     
>  
>     I started with a non-modified Franceformer  15/60 before I kept cramming 
> too much power into the 6" secondary. 
>  
>   
>> I'm planning on basically an 11kV/200mA NST of which will be  rectified with 
>>     
> 15kV/540mA HV diodes >(full bridge configuration using 4  diodes).
>  
>     With a standard full-bridge rectifier, each  leg sees the peak voltage 
> from the AC supply.  So with your 11kV AC NST,  each leg of the bridge will have 
> to be rated at an absolute minimum of 11  kV * 1.414  = 15.6 kV. That's not 
> counting all the "funny" stuff  from NST inductance, harmonics, static 
> discharges, corona, and transients from  all the high-current discharges running 
> around. Not to mention the biggest  killer of my rectifiers - direct secondary 
> strikes!
>     I made each leg of my bridge out of 40 1kV  1A diodes seriesed. These 
> were fast-recovery (75nS) UF4007's, My thinking was  that their fast-recovery 
> would block any RF from getting back to the power  supply. 
>     I also put a 200 Ohm 100W resistor in each DC leg  off the bridge. I 
> later replaced two legs with "bar" rectifiers that came from  a 3-phase rectifier 
> for the HV power supply of an AM radio station. Two weeks  ago I killed one of 
> those "bars" from a direct secondary strike. 
>     I'm getting annoyed enough that my next move will  be to recycle the 
> rectifier assys from my XRT, and protect everything with  a zillion TVS's...
>  
>   
>> I'll be using 6 boards, so there will be some decent power to deal  with. 
>>     
> I'm just curious if anyone's >been down this road that I'm traveling  and could 
> offer any advice on high power 
>
>   
>> into the SISG.
>>     
>
>
>     6 boards with 4 sections each will just sit there  and twiddle its thumbs 
> until you hit 15.3 kV. Trust me, no current draw, no  sparks, no _nothing_ 
> until the voltage across the 6 x SISG4 hits the nominal  21.6kV peak. I've got 
> old-school amp and volt panel meters for the Pig primary,  and there's a magic 
> point at which suddenly it all happens. Yes, disconcerting  when you're used 
> to ramping up spark-gap coils! But you won't get any results  unless you use 17 
> sections (4 and 1/4 boards), or 5 boards if you boost the NST  primary with a 
> variac. 
>     Remember, there's no resonant rise because the  rectifier is blocking it. 
> Anything like level shifting or boosting it with a  choke would give you more 
> voltage than you need, eh?
>  
>     BTW, where did you get an 11/200 NST??
>  
> -Phi LaBudde
>