RE: DRSSTC, OLTC, OL-DRSSTC, M.I.C.,K.E.Y M.O.U.S.E. TC... Re: ALF: why not DRSSTC?

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Rich" <rdjmgmt@xxxxxxxxxx>



Thank you Terry, there are a few people, like me, who like to build
things but are still stuck in the "old" spark gap way. We either don't
have the money or smarts to go DRSSTC, OLTC, OL-DRSSTC, M.I.C.,K.E.Y
M.O.U.S.E. TC.... Make it simple and you will get more into coiling. It
is great to read about all the new things but many people can not afford
all the equipment that is used to build some of today's coils so a
simple one now and then does help. Keep pushing the envelope at your
end.

Cheers,
	Rich, kd0zz, from the middle of Missouri

Subject: DRSSTC, OLTC, OL-DRSSTC, M.I.C.,K.E.Y M.O.U.S.E. TC... Re: ALF:
why not DRSSTC?

Original poster: Terry Fritz <vardin@xxxxxxxxxxxxxxxxxxxxxxx>

Hi Greg,

At 04:35 PM 9/24/2005, you wrote:
>Hi Jimmy, Steve, Terry,
>
>
>Part of the problem I have had in grasping the OLTC and DRSSTC
>concepts is that I haven't found a concise one-sentence description
>for either of them.  For instance, I had thought that OLTC addressed
>the techniques for 'Off-Line' operation of a Tesla Coil.  Does the
>term also refer to the general case where a single solid-state
>device replaces the spark-gap in a classic impulse-type Tesla Coil?

When originally made, the OLTC had these distinctions:

1.  The primary firing voltage was just the rectified AC line
voltage.  The AC line and a rectifier charged the primary capacitor
"directly" to say 340 volts.  That "was" the firing voltage!!  Later,
a resonant inductor helped to almost double that voltage.  But there
is NO high voltage transformer used to charge the primary cap.  The
primary voltage "never goes higher" than the primary cap voltage.  It
works right "off the line" voltage, but can still produce "big" coil"
outputs.  Unlike say a tube or transistor coil, the OLTC was still a
full powered disruptive coil.

2.  Since the primary voltage is low, "enormous" primary currents are
used to impart the power on the secondary.  Mine was designed for
7000 peak primary amps!!  Thus, a very large primary capacitance and
a very low primary inductance was needed.  The OLTC operates in the
many thousands of primary amps range.  The "Key" that started it all
was modeling with Mark's MandK program that showed a "single turn"
(low inductance) primary would still have "enough" coupling.  That
meant the high currents at low voltage could be used to duplicate a
standard high voltage primary coil's magnetic field and deliver it to
the secondary.

3.  IGBTs allowed for relatively low loss switching of low voltages
but at super high currents.  Now that the voltage was "low", standard
big IGBTS could be used.  With the primary voltage in the 700V peak
range, just "off-the-self" power electronics could now be used.  By
over driving the gate voltage to the 20 to 25 volt range, the IGBTS
could be hit with up to three times their rated peak current (and
they liked it ;-)).  A reverse diode allowed for reverse current flow
and the IGBT could hold the system back until the time was just right
to begin (also a major idea!!)).  The low duty cycle kept device
heating low.  The "spark gap" was now silent and dark...

4.  The OLTC was the first big coil that had very high power with
precise timing and quenching "electronically" controlled.  Without a
spark gap, it could fire time after time with almost perfect
repeatability.

 From afar, the OLTC stood out as a "big coil" that had an
"electronic spark gap" and "no high voltage transformers".  The
"whole thing" weighed 40 pounds...  In England, where HV transformers
are much harder to get, they really went to town!!!

Steve Conner took the OLTC to it finest form in his OLTC-II:

http://www.scopeboy.com/tesla/ol2derby/pics2.html

Derek has also done great work on them!

http://www.roffesoft.co.uk/tesla/oltc/oltc4.htm

Finn just made one, but I don't have the link handy.

The OLTC is nice where not too giant sparks are needed but a reliable
"big" "solid state" coil is...


Then came "Jimmy and the DRSSTC"  :-)))  Coiling will just never be
the same...  Jimmy took all the tricks of the OLTC, and used them to
"change everything!!"  He gets the current "Nobel prize in Coiling" ;-))

1.  The line voltage now charges a big buss capacitor for virtually
"unlimited available energy" "during a bang".  Still an "off-line"
machine with no transformer, but now we can draw as much power as we
want inside the firing cycle.  All the old rules about "limited" bang
energy get thrown out...

2.  The primary coil and capacitor voltage is now "resonated" to far
higher voltages by an "H-bridge" of IGBTs.  The push-pull H-bridge
forces current into the primary circuit.  That current builds up high
voltages on the primary through resonance, but those voltage are
still safely far away from the IGBTs and other
"electronics"!  Suddenly, we have our high voltage primary back with
far lower losses than the OLTC primary.  We no longer need giant
primary currents eating vast amounts of power in losses.  Of course,
we "still can" run giant primary currents to get like "12 foot arcs"
from a "solid state coil" :-))))    BTW - Steve still is not using
his "BIG" IGBTs :o))))

3.  The DRSSTC actually reuses un-needed power buy restoring energy
back into the buss caps when the coil is quenched.  We usually don't
give that much thought, but you should (as you have!) for a giant
machine...

The OLTC broke a lot of ground and introduced a lot of new technology
and options.  But, it never was a "perfect" machine.  They are
frightening monsters that pack a lot of power and electronics (no one
goes near them ;-)), but they could not "beat" a conventional
coil.  The low primary voltage and high currents just are too lossy
in the primary...   They are remarkably reliable.  Aside from fried
secondaries, I am not sure if the primary drive side has "ever" been
reported to fail???

BUT, the DRSSTC can beat any machine out there!!!  It directly solved
the two problems of the OLTC!!  The technology is much like any high
power switching power supply and so are the electronics.  For many
power electronics engineering types, coiling just got easy
;-))   There is an ever growing number of them.  They even have their
own website :O)):

www.drsstc.com

Right now, DRSSTCs are where all the action is at!!!

But, there is "still a problem" with DRSSTCs.  They are not "simple
and easy"...  PC boards, ICs, digital scopes, current probes, EE
degrees (or in the process of getting them), and MONEY...  DRSSTCs
ARE a complex business!!  And not cheap...  I spent about $1600 on
mine (http://drsstc.com/~terrell/) but I went all out...  Maybe I
have the record of most dollars spent on one :O))  But mine has
microprocessors, fiber optics, optical gate drive, multiple
selectable software modes...  Dan wrote "The Book!!".  Steve has "the
big one".  Jimmy is the "god"...

I think Steve is the driver master ;-)

http://www.scopeboy.com/tesla/drsstc/dr3_1.gif

And the other two sheets!!

http://www.scopeboy.com/tesla/drsstc/dr3_2.gif

http://www.scopeboy.com/tesla/drsstc/dr3_3.gif

:-))))

So, these days, "I" am trying to make them "dirt simple"...  COTS
parts...  No ICs...  VERY cheap ;-)))  Maybe "any noobie kid" will
soon be able to make one ;-))

Cheers,

         Terry