Hi Wil,
On Sun, Nov 16, 2014 at 12:17 AM, William Howard <snakeprior@xxxxxxxxx>
wrote:
> Dear Steve,
> I am lost for words.
>
> Is there anyway this QCW stuff can be applied to spark gap or VTTC?
>
> QCW (since I didnt define it earlier) stands for Quasi Continuous-Wave,
which means that i have a tesla coil operating in a steady-state mode, but
im continuously modulating the supply voltage to it. Spark gap TCs are
definitely not operating in steady state, and there isnt a clear way to
apply this modulation technique to them. VTTCs however can operate CW, but
you could claim any VTTC fed from unfiltered power is "QCW". The term QCW
came about when i built an electronic modulator (commonly known as a "Buck"
converter, but operating very quickly and at high peak power) to feed power
into my typical SSTC circuit. The idea was that 60hz line waveforms gave
some distinct performance advantage over CW or interrupted CW due to the
ramping in supply voltage. So instead of being limited to a 8.33mS ramp
that a perfect level shifter might produce for a VTTC, i could ramp for
10's of mS growing sparks much longer than a line-operated VTTC/SSTC ever
has. Ramping the voltage up too fast causes sparks to bend and split more
often, so having a long ramp time can be very beneficial in reaching long
distances.
My friend Phillip built a "QCW modulator" for his 833C VTTC. He pushes the
tube to extremes, but managed something like 60" discharges from his coil
this way. The modulator in this case was a different type of DC-DC
converter using a HV ferrite transformer to boost the voltage to 12kV i
believe (far higher than the 5-6kV from a level shifter and a MOT!).
Phillip called it the SSVC or "solid state vacuum tube coil", there are
some pics of it on his flickr:
https://www.flickr.com/photos/pslawinski/sets/72157623355812229/
Id say there probably arent any quick/easy ways to make a QCW modulator, it
will require some reading up on DC converters and then understanding how to
apply it to tesla coil loads. Phillip's modulator was probably more
complicated than the rest of the VTTC. This is likely why you dont see any
other examples of it in the hobby.
Very impressive results.
>
Thanks!
Steve
>
> -Wil
> On 16/11/2014 11:43 AM, "Steve Ward" <steve.ward@xxxxxxxxx> wrote:
>
> > Hey Guys,
> >
> > I've been playing with larger arrays of fast-switching IGBTs for growing
> > huge arcs from "tiny" coils. The idea is that hotter plasmas can be
> > achieved at lower voltages by upping the frequency. At ~350Khz and
> above,
> > its noted that the plasma tends to grow in straight segments which helps
> it
> > reach further still... A dramatic demonstration of this effect is shown
> > here with an 8" long coil with just 165 turns of wire producing maybe
> > 100kVAC at 300khz is jumping 11 feet to the shop ceiling.
> >
> > https://www.flickr.com/photos/kickermagnet/15705193211/in/photostream/
> >
> > More pics at:
> >
> >
> >
> http://forcijo.smugmug.com/Events/Teslathons/Philthon-2014/45663076_MtFqHw#!i=3689589842&k=M8Crsgs
> >
> > For those into the specs on components and such, I'll link my 4HV.org
> post
> > from earlier today:
> >
> > http://4hv.org/e107_plugins/forum/forum_viewtopic.php?167363
> >
> > This coil is waiting for a 40kW power supply before it can sustain the
> 10+
> > foot performance at high duty cycle. For now its limited to bursts at
> any
> > power level over 15kW (which can only produce about a 5-6 foot discharge
> at
> > 50% "on time" or about 25% duty cycle considering its a triangular
> > modulation signal). Maximum peak power so far is 190kW. The maximum i'd
> > bet my power electronics can handle is 260kW peak, so i think 13-14 foot
> > sparks may be possible from my 8" tall winding... i'll set it up with
> more
> > space next time and see :-).
> >
> > Steve
> > _______________________________________________
> > Tesla mailing list
> > Tesla@xxxxxxxxxx
> > http://www.pupman.com/mailman/listinfo/tesla
> >
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