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Registered Member #51
Joined: Thu Feb 09 2006, 04:17AM
Location:
Posts: 263
Those results with a primary current of only 140A are very impressive. I am surprised you chose to use mini bricks for a current that low. Don't the to-247 devices handle 200A or so? Perhaps you have plans to build a bigger coil using this idea? I was also surprised by the fact that you used a synchronous buck converter, If i do attempt this type of coil, I will probably just use an ultrafast diode in place of the second switch.
Registered Member #1637
Joined: Sat Aug 16 2008, 04:47AM
Location: Kiev, Ukraine
Posts: 83
The physics is quite simple, I guess.
Firstly, you create plasma channel and heat it up. When plasma forms, it loads secondary and prevents excessive voltage rise - thats why streamer doesnt strikes into primary or strike ring.
Secondly, when air get ionized, you apply more power, and thus compenase for losses. The easiest way for current to get closed is to propangade throuh ionized air.
The streamer is held in vertical plane by toroid's field and, I think, you can get even longer sparks by increasing toroid's diameter.
And question again - what coupling do you use? I expect it to be near 0.4 or so. Quite impressive!
Registered Member #2566
Joined: Wed Dec 23 2009, 05:52PM
Location:
Posts: 147
Just on the contrary.The physics involved is quite complicated. Many of the things ,especially regarding optimization of the driving mode for the longest possible spark: a) given peak voltage b) given peak power and frequency
Registered Member #146
Joined: Sun Feb 12 2006, 04:21AM
Location: Austin Tx
Posts: 1055
The streamer is held in vertical plane by toroid's field and, I think, you can get even longer sparks by increasing toroid's diameter.
I used to agree with that, but not anymore. The streamers are more than 6X the diameter of the toroid, certainly not "near field". The propagation is fairly independent of the toroid field i believe.
BTW, its not that i dont have any clue about the plasma stuff, im just not willing to claim that i understand it. So very basic observations are not likely to benefit *me*.
Those results with a primary current of only 140A are very impressive. I am surprised you chose to use mini bricks for a current that low. Don't the to-247 devices handle 200A or so? Perhaps you have plans to build a bigger coil using this idea? I was also surprised by the fact that you used a synchronous buck converter, If i do attempt this type of coil, I will probably just use an ultrafast diode in place of the second switch.
ONLY 140A?? I think you miss the implications of running long pulses, there is serious heating of the device. Though i did run similar conditions of about 80A peak using some TO-247 transistors and got to 45" sparks running them right at 600V bus, where they then failed (not unexpected).
BTW, i should mention that im over the whole idea of pushing parts way beyond their reasonable limits. It really doesnt get you anywhere in the long run.
Registered Member #195
Joined: Fri Feb 17 2006, 08:27PM
Location: Berkeley, ca.
Posts: 1111
Hello Steve, it seems that the rather large primary has the added effect if increasing your coupling, do you think that that helps in power transfer to your spark since you use a system that is geared to a CW operation? It seems that your primary and secondary is more efficient than a regular setup. Because your tesla primary is a high impedance primary and you use less current do you have to increase the amount of voltage to make up the wattage or do think the coupling is good enough or both
Registered Member #1225
Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253
BTW, i should mention that im over the whole idea of pushing parts way beyond their reasonable limits. It really doesnt get you anywhere in the long run.
I am hereby revoking your coiler license!
My guess was that the plasma that forms when the buss voltage is low acts like a breakout point for the next increase in steamer size and so on. Whatever if i am wrong, i have it all worked out in my mind, how i think it would happen. I can just kinda visualize it working. I am weird like that.
Registered Member #639
Joined: Wed Apr 11 2007, 09:09PM
Location: The Netherlands, Herkenbosch
Posts: 512
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.
Registered Member #2161
Joined: Fri Jun 05 2009, 03:36PM
Location:
Posts: 247
Personally, I find it quite cool that you are not disclosing the exact way in which the QCW works. I think it may be grounds for a challange of sorts for all the coilers on the forum.
Basically we all start designing/experimenting on making a coil similar to Steve Wards and at a set point (3 months or so), we open a thread with pictures and disclose how we came to the result. I think it would be quite interesting to see how the different minds on this forum each had their own way of achieving the "Prancing Sword" style tesla coil?
What do you guys think about that? Personally I am already hunting for some mini-bricks or an extremely fast 32mm packaged brick, as to-247 and 264 just aren't going to cut it on the thermal front, as Steve mentioned.
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Steve's Q.C.W coil design
I can just kinda visualize it working. I am weird like that.
