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>
 >
 > Hi Dave, i will try to answer your questions:
 >
 > >------------------------------
 > >I suspect the delays are from your cascaded GDT's.
 >
 > Cascaded?  I think you may have misunderstood my driving scheme.  In the
 > schematic i have a TC442X pair driving a small GDT.  This drives 1
 > half-bridge (which makes up one beefy gate driver).  This half-bridge ALONE
 > drives ALL 16 mosfets.  There is one large GDT per each 4 fets. So 4 gate
 > drivers, all of their primaries connect to that half-bridge.  There is no
 > cascading of GDTs.
 >

---------------------------------------
I understand this now.  A couple more power circuit questions:
1.  What FET are you using?
2.  What is size, type and voltage rating E storage cascade capacitors
      are you using?
3.  What blocking diode are you using (P/N, voltage current fast
      recovery, etc.)?
4.  On each GDT winding to FET, what value resistors are you
      using for gate, gate pull down, and are you using zener (or
      bi-directional) clamp between gate and source of each FET.

Thanks for the info...
-----------------------------------------

 >
 >   Maybe a high
 > >power
 > >current loop with indiividual I>V converter transformers at each switch
 > >pair may reduce delays and losses.
 >
 > If i knew more about electronics i would be able to follow you... to tell
 > you the truth, im a freshmen in college and havent take a single course in
 > electronics yet.  I *THINK* i understand what your saying, but im not sure
 > how to design/implement this.

----------------------------------
Basically wind the primary ONLY on a ferrite toroid.  Pass through the
window of the primary toroid a high current copper loop (1/8 to 1/4"
copper tubing is perfect).  At each driver PCB have a toroid with number
of windings for each FET.  Copper tubing would pass through each
of these FET drive toroids.  The copper tubing makes a one turn loop
through the window of all the toroids.  The GDT driver now drives the
entire high current loop, and thereby drives each driver board.

The advantage of this idea is one HUMONGOUS driver could drive 4X
as many drivers and they would be synchronized fairly well to each other.
This would simplify building the isolated gate transformers, and if the
copper tubing is passed through a thick wall PE tubing ( polyflow(R) )
through the interior of the toroid, very good HV standoff (perhaps
5kV or more) could be achieved, cheaply using off the shelf stuff
from Home Depot, Lowes, Wal-Mart, etc.

An another way to visualize; imagine a pistol soldering gun, with the
powering transformer as one toroid, and the local "load" toroid
transformers are placed on high current loop like stringing beads
on a string.
----------------------------------------
  <SNIP>

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...   :^?

 >
 > Umm, start calculus this semester soo...
 >
 > anyway, this IS a full bridge!  If you look at my page im using two 4 level
 > inverters and are running oppositely of eachother.  Its effectively a full
 > bridge to the best of my knowledge.  I basically did this because normally,
 > the output of a single inverter would go through a DC blocking cap- through
 > a load- then back to ground/neutral.  I didnt like the idea of that, so i
 > built another inverter to go on the other side of the load.

-------------------------------------
Ok, imagine your circuit, but build a mirror image with bottom 4X drivers
tied to (-) power with neutral (+).  Tie together at a terminal with two AC
caps.  Repeat on other side of bridge.  While one diagonal pair of drivers
are discharging (driving) the load, the opposite pair are charging the caps,
Diagonal drivers swap, now vice versa diagonal pair is driving (in opposite
direction) while previous discharging drivers are now charging.
Vo-N = V*4stages *2  (+/- pk).  So if you doubled number of existing
stages on your current design, voltage would be doubled (at load) but
each driver would still see 4X Vin stress; but most importantly 2X the power.
Can sketch up a drawing a Excel to clarify.  I also ran a manual switch
simulation in Multisim and it worked no problem...  :^)
------------------------------------

 > >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!
 >
 > Im not sure what a voltage adder is, example?

Look up "Fractional Turn Transformer" in Google.  Imagine 4 large identical
toroids. Wind 1 turn from you present driver (4 in parallel) around each 
toroid.
Then wind 'X' turns around _ALL_ four toroids.  Vo ~Vin * 4 * Xturns.  Dunk
whole assembly in oil.  Now what's limiting your drive output voltage?  This
technique is used for linear accelerators, and Klystron drivers.  This "drive"
transformer Vo could directly feed the base of the resonator.

 > 30-60kv base drive sure would allow for some massive powers to be pushed
 > into the resonator, but this sounds like a daunting feat.
 >
 > Dave, I hope we are starting to get clear with eachother on this topic.  My
 > limited knowledge doesnt help things, but im trying ;-)

Steve, you are doing outstanding.  A reality check, I am very impressed 
with your
projects to date, and your successes with your knowledge base.  Your 
willingness
to try new things and "Just do it!" will serve you well in the future.  I 
wish you
much success in your studies and future endeavors.

 > Steve

Best Regards
Dave Sharpe, TCBOR/HEAS
Chesterfield, VA. USA