Re: SSSSTC Coil questions for Mr. Steve

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: David Sharpe <sccr4us-at-erols-dot-com> 

Hi Steve!

Tesla list wrote:

 > Original poster: "Steven Ward" <srward16-at-hotmail-dot-com>
 >
 > Dave,
 >
 > I will add the schematics soon.  I have them made, i just need to upload
 > them to the site.
 >
 > Anyhow, there IS a big delay from all the stages in the circuitry.  About
 > 700ns from the feedback going high, until the mosfets are ON... yikes... i
 > know what people are thinking, that is bad!  Well, its still working,
 > though im sure im hard switching a bit of current due to this.  Im not sure
 > how to remedy this (aside from reducing the delays as much as
 > possible).  Perhaps a phase shifting circuit could work, but im not sure if
 > i like the idea of that... seems like a good source of headaches.
 >

------------------------------
I suspect the delays are from your cascaded GDT's.  Maybe a high power
current loop with indiividual I>V converter transformers at each switch
pair may reduce delays and losses.  I would also look at possibly combining
stages in next attempt, as example, IDK if you really need the 74LS14
inverters, you may have enough drive from LT016 to direct drive the
TC4420's.

I need a litle more detail with your GDT configuration, (core, number of 
turns),
I assume you are using one per FET totem pole, with 4 primaries paralleled
to master driver?
-------------------------------

 > At one point i did ponder adding on more stages to the output using
 > IRFP460s.  It seems to me that the law of diminishing returns would apply
 > here.  Basically the idea with the higher voltage was to get an easier
 > impedance match between the coils (so im not using a 2 turn primary or
 > something).  Also, reduce other primary losses (though im sure they are
 > extremely low in a SSTC).  I tested the cat 5 wire that i used for the GDTs
 > with a 9kv NST running 140V input.  It sadly outlasted the NST!  i came
 > back a few hours later and my NST was dead while the wire was still 
prestine.
 > The test was simply a twisted pair of conductors, each going to one side of
 > the NST.  I know things get much different at 115 khz, but the cat 5 sure
 > has proven itself to me!
 >

Perform a little calculus and determine where the 2nd derivative (most rapid)
slope change is.  I agree with you, you are probably at diminishing returns 
with
4-5 stages (8-10X Vin multiplication).  Another idea struck me with this
design, you might be able to turn this topology into a full bridge and double
applied voltage again.  Need to think about it a little more...   :^?

 > I still need to work out some details, then i can run this machine up to
 > 240 and possible 280VAC input for about 1580V (3160Vp-p) on the
 > primary.  Watch out!

Another possibility is build a "voltage adder" circuit using multiples of this
circuit to drive a driver transformer cascade.  Imagine what could be done
with 30-60kV pk going into base of resonator like a magnifier!

 > Steve

Regards
Dave Sharpe, TCBOR/HEAS
Chesterfield, VA. USA
<SNIP>