Dear Steve,
Thanks for the explanation. This I think explains the huge difference in
spark length I get from different coils I've made.
I got the longest CW (50cm) out of a 380 turn secondary which has a wound
length of 19.5cm. It has a very high inductance primary (54 turns) and
tight coupling with low tank capacitance (75pf) and a large topload (20cm
dia ss bowls).
I tried and tried to replicate it with different coils and different tank
circuits but got stuck at 15 to 20cm.
So I think this QCW is the reason why. Some how my spark is growing in
length at the right time but I am not actually producing more voltage.
You have inadvertently saved me from a headache of trying to figure out
whats going on!
Cheers!
-Wil
On 17/11/2014 4:25 AM, "Steve Ward" <steve.ward@xxxxxxxxx> wrote:
> 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
> > >
> > _______________________________________________
> > Tesla mailing list
> > Tesla@xxxxxxxxxx
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> >
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