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Steve's Q.C.W coil design

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cjk2

Tue Mar 23 2010, 03:58AM

Registered Member #51 Joined: Thu Feb 09 2006, 04:17AM
Location:
Posts: 263

Yes, I have been working on designing a full bridge, Driver, Class D amp, etc. Since I saw the pictures that Steve posted. I am going for to-247 based design to start, if I blow that up and don't get at least 40" or so, I will move up to minibricks :)

Mates

Tue Mar 23 2010, 01:28PM

Registered Member #1025 Joined: Sun Sept 23 2007, 07:53PM
Location: Czech Rep.
Posts: 566

Dalus wrote ...

My guess would be that a ramped wave form of the bus voltage allows for a slower growth of a streamer. There is more energy put into a smaller distance of streamer then with a conventional DRSSTC. The more energy in a streamer the hotter it is and the longer it stays ionized. This is just a guess but it might be a nice project to research this with highspeed camera's whilst measuring different parameters of the coil and trying to figure out a relationship between them.

Actually I see it in exactly opposite way. Why classical CW SSTC does not produce long streamers? The answer might be in too much of energy in the beginning of the streamer. I think you don't need too much of energy to start the streamer but after it is started you need to pump more and more energy to keep it "alive" I see the bus modulation something like this:

Turkey9

Tue Mar 23 2010, 02:19PM

Registered Member #1451 Joined: Wed Apr 23 2008, 03:48AM
Location: Boulder, Co
Posts: 661

With that wave form you would be ramping the power, not the voltage... makes sense because the total power is what needs to change, so just increasing voltage isn't the only way to do it. PWM the bus would be easier too in my mind.

Dr. Drone

Tue Mar 23 2010, 04:02PM

Registered Member #290 Joined: Mon Mar 06 2006, 08:24PM
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Posts: 1673

brtaman

Tue Mar 23 2010, 04:06PM

Registered Member #2161 Joined: Fri Jun 05 2009, 03:36PM
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Posts: 247

GeordieBoy wrote ...

A challange sounds like a good idea. I've already thrown out all my solid-state gubbins and started investing in those infamous 4CX250B's !

-Richie,

I will do you one better I am saving up for a couple 4CX1000As I will parallel all of them...you guys will have nothing on me...!

ScotchTapeLord

Tue Mar 23 2010, 04:11PM

Registered Member #1875 Joined: Sun Dec 21 2008, 06:36PM
Location:
Posts: 635

Mates wrote ...

Actually I see it in exactly opposite way. Why classical CW SSTC does not produce long streamers? The answer might be in too much of energy in the beginning of the streamer. I think you don't need too much of energy to start the streamer but after it is started you need to pump more and more energy to keep it "alive" I see the bus modulation something like this:

If too much energy in the beginning of the streamer caused poor sparks, then the SGTC would not be very impressive, considering its damped waveform... Though it seems to me that the DRSSTC has the opposite waveform from the SGTC, yet both produce similar effects.

Steve Ward

Tue Mar 23 2010, 04:32PM

Registered Member #146 Joined: Sun Feb 12 2006, 04:21AM
Location: Austin Tx
Posts: 1055

The streamer impedance is dynamic vs time and length (volume). IF you try to grow a long streamer in a short amount of time, you need a tremendous voltage to do it. If you allow the streamer to grow over a very long time, the voltage requirement can be much lower. Applying the right dv/dt to the spark as im doing in my system appears to yield extremely efficient spark propagation at fairly low voltages (less than 100kV i still claim).

If too much energy in the beginning of the streamer caused poor sparks, then the SGTC would not be very impressive, considering its damped waveform... Though it seems to me that the DRSSTC has the opposite waveform from the SGTC, yet both produce similar effects.

I claim the mechanism for spark growth is different from a "transient" coil like a SGTC or fast DRSSTC. In a DRSSTC, if you use a low enough tank impedance you can get similar secondary energy ring-up times as a SGTC. I do not see a "fast" DRSSTC as being much different than a SGTC. I think in terms of efficiently growing sparks *fast* the SGTC wins because it dumps the energy into the secondary faster than most DRSSTCs can withstand (the silicon is a limit). On my large experimental DRSSTC i used a 1.25uF tank cap and was able to get 12 foot sparks with just 5 RF cycles of drive. I think the secondary voltage rise time was on par with SGTCs.

Someone asked about coupling. Of course higher coupling is better in a steady-state energy transfer sense. It essentially means that you have less "reactive" energy stored in the primary. If i was to lower the coupling, id have to greatly increase the primary current to achieve the same results. If i thought i could get away with higher coupling, i probably would. I think the K is around .5 to .6 right now. I do get an occasional flash-over from the side of the secondary to the primary, but so far none of them have been very destructive. I think my over-current detector catches the condition pretty quickly before much energy can be put into the arc, which is also sort of a nice consequence of the higher coupling.

dex

Tue Mar 23 2010, 08:54PM

Registered Member #2566 Joined: Wed Dec 23 2009, 05:52PM
Location:
Posts: 147

Steve Ward wrote ...

Applying the right dv/dt to the spark as im doing in my system appears to yield extremely efficient spark propagation at fairly low voltages (less than 100kV i still claim).

If the frequency is below 500 khz,no matter what you do,and what driving mode you use,you will not get more than 5 foot long air sparks with less than 100 kV.That's not possible at normal altitude.That's what I claim

Patrick

Tue Mar 23 2010, 08:57PM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

Dam steve, once again you prove yourself to be an ace of the coiling. QCW is masterful in form and function. Yeah, i bet people stealing your work and not putting much of there own effort in, ticks you off.

-Patrick

Coronafix

Tue Mar 23 2010, 09:05PM

Registered Member #160 Joined: Mon Feb 13 2006, 02:07AM
Location: Melbourne, Australia
Posts: 938

Dr. Spark wrote ...

About 40 years ago used two 4CX250B with a class D-AMP (All tubes), 75 foot sparks were accomplished. The coil was built for someone in Australia; however, had to sign a non disclosure agreement not to give any information of pictures or location.

Cheers,
Dr. Spark

40 years ago huh?....75 foot sparks!....mmm....
must have been for the Pine Gap secret UFO base that is accessed by submarines through the secret
tunnels under the Great Australian Bight.

Perhaps 75" sparks? Or perhaps it really is disinformation.

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