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Re: Sold state IGBT disruptive coil spark gap idea

Original poster: Vardan <vardan01@xxxxxxxxxxxxxxxxxxxxxxx>

Hi Dan,

I have been going by:

Pd = Irms^2 x 0.05 pre section

Mot coils have fewer sections but higher Irms where say a NST has more sections but lower Irms.

Beware that the lower losses increase Irms significantly.

Also, the 220k + 1pF/foot model seems to not quite work. The streamer load seems less in these coils so they ring longer. I would count on the ringdown time being without any streamer load and adjust R4 for the longer time. I am using 2.2k for 400uS.

Also, I found that if you turn up the voltage too high on a MOT system the gap will fire at say 480BPS rather easily as opposed to 120BPS. That increases heating 4X (!) without much increase in streamer length at all.

I have very small ~1 inch square heatsinks and they stay reasonably cool. But one should consider larger ones or go to fan cooling in many cases.

I have a ton of new stuff to write up.... But everything is now working as it should.



At 09:04 PM 5/21/2006, you wrote:

What are the calculated losses in the actual solid state switch? Just curious how these losses stack up (however minor they may be) when you
start series'ing a lot of the gaps together.


Daniel McCauley
DRSSTC : Building the Modern Day Tesla Coil Book
Check it out at http://www.drsstcbook.com

Hi Gerry,

With the new inductor and all, it hits 22 inches about twice/second. Probably could hit 23 easily and maybe 24 inches. The exact primary power is 117W.

The Freau number in that case would be 2.22 but I am using actual capacitor energy x BPS instead of "wall plug" watts. The above number agrees with DRSSTCs.

Probably the biggest power loss is, oddly, in the secondary coil's Rac at about 450 ohms.

The not ground hit ringdown is longer than expected so the IGBTs may be burning excess power due to the 250uS turn off time possibly being too short.... More to study there...



At 12:56 AM 5/21/2006, you wrote:
Hi Terry,

Nice set of pictures. Is your 115 watts wall power or at the SISG (bang energy * BPS)??? Please tell us what the maximum spark length is when you measure it.

Gerry R

Original poster: Vardan <vardan01@xxxxxxxxxxxxxxxxxxxxxxx>

Hi All,

I tested the SISG gap and coil out tonight at 116 watts and it works fine ;-)) Firing voltage was 3600V 150nF 120BPS 105kHz...

Here are the new boards all mounted up pretty:


Here are the MOTs.  Didn't have time yet to mount them up nice:


6000V  150nF MMC:


Bridge rectifier:


Here it is arcing nicely to a point 15 inches away. It could have gone further:


Here is a little 14Meg movie I put on rapidshare.de:


Go to the bottom and click "free", Wait about a minute for the countdown timer, type the funny letters in the box and download it. You don't have to log on or pay anything.

I ran into a charging loop problem so I stopped for the night (tired :-p). But the SISG gap is working perfectly!!! The heat sinks barely get warm. I never used any ballasting.