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Registered Member #61428
Joined: Sat Jan 14 2017, 12:39PM
Location:
Posts: 50
Ever since I leaned that Q values in excess of a million are possible with crystal resonators I have wondered if there might be a way to design a crystal power oscillator that would operate something like a Tesla coil with the conventional secondary circuit replaced or supplemented by a crystal with potentially several orders of magnitude greater Q factor. I've tried simulating a few schemes where I basically placed the crystal below and in series with the topload of a conventional coil with very underwhelming results. I know essentially how to simulate the behavior of a crystal but I'm still not grasping something here.
Can any of you think of any way this sort of thing could work? Is there even any merit to the idea?
Registered Member #834
Joined: Tue Jun 12 2007, 10:57PM
Location: Brazil
Posts: 644
Tesla coils don't depend on the quality factor of the resonator. Too low quality factor creates losses, of course, but after a quite low value there is no more difference.
Registered Member #61428
Joined: Sat Jan 14 2017, 12:39PM
Location:
Posts: 50
Antonio wrote ...
Tesla coils don't depend on the quality factor of the resonator. Too low quality factor creates losses, of course, but after a quite low value there is no more difference.
What are you talking about dude? That's like saying a Tesla coil resonator doesn't depend on resonance. A TC secondary circuit is always designed to have the highest inductance, lowest series resistance, and thus the highest Q factor possible. Voltage gain from input to output, neglecting losses will depend on the root of the ratio of Ls to Lp and the voltage gain within the secondary circuit when driven at resonance is equal to its Q factor. Thus, the secondary Q should be as high as practical. Q factor IS a factor of the final gain product. That is, ignoring dynamic loading effects, a coil with a secondary circuit Q of 200 will have twice the voltage gain of a coil with a Q of 100.
Maybe you and I just have different ideas on what constitutes a low Q value. The only ways it could be <<100 would be:
A) If your secondary wire is too small, or not copper B) If your secondary turns are widely spaced or too few in number C) If your secondary coil has insufficient height or diameter D) If you deliberately add series resistance or shunt conductance to broaden the bandwidth or otherwise limit performance
TC secondaries actually have similar inductance and ESR to quartz crystals in the ~1MHz operating range, but crystals generally have series capacitance measured in fF.
The only type of crystal I can think of that could stand up to such extreme electrical and mechanical stress would be the igniter type, but I have no clue what kind of Q factors they'd have. Judging by their size and shape, they probably resonate at too high a frequency to be useful anyways. I would probably have to cut or grow some special.
Perhaps a cavity resonator would be better suited to stand in as a tertiary magnifier circuit. I'm sure it's been tried, but as for the crystals, there is very little information.
Any links to info on piezo-transformers or anything else along these lines would be appreciated.
Registered Member #162
Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140
from memory of my coils; . before breakout "Q" = 100 to 500 . during breakout ... really not sure but guestimated at 3 to 10
Here I use the definition of Q = (reactive power) / (real power) sometimes I use Q=(resonant frequency)/(3dB bandwidth)
so if you have a piezo/resonant transformer with a loaded/working Q of 10,000 giving a hv output of 1kW then the reactive power would be 10 MVAR or if you think of it as Q=(reactive resonant current)/(resistive load current) a 1A output current (arc) would require a resonating current of 10kA for a loaded Q of 10,000 the physical constraints are quite stringent.
Registered Member #834
Joined: Tue Jun 12 2007, 10:57PM
Location: Brazil
Posts: 644
Enceladus wrote ...
What are you talking about dude? That's like saying a Tesla coil resonator doesn't depend on resonance. A TC secondary circuit is always designed to have the highest inductance, lowest series resistance, and thus the highest Q factor possible. Voltage gain from input to output, neglecting losses will depend on the root of the ratio of Ls to Lp and the voltage gain within the secondary circuit when driven at resonance is equal to its Q factor. Thus, the secondary Q should be as high as practical. Q factor IS a factor of the final gain product. That is, ignoring dynamic loading effects, a coil with a secondary circuit Q of 200 will have twice the voltage gain of a coil with a Q of 100.
No. The maximum voltage gain in a conventional Tesla coil, modeled as two coupled LC circuits, is given, by energy conservation, as que square root of the ratio between primary and secondary capacitances, or, equivalently, by the ratio between secondary and primary inductances. High Q in the coils can't increase this gain. Low Q can reduce it, of course.
Registered Member #61428
Joined: Sat Jan 14 2017, 12:39PM
Location:
Posts: 50
Antonio wrote ...
Enceladus wrote ...
What are you talking about dude? That's like saying a Tesla coil resonator doesn't depend on resonance. A TC secondary circuit is always designed to have the highest inductance, lowest series resistance, and thus the highest Q factor possible. Voltage gain from input to output, neglecting losses will depend on the root of the ratio of Ls to Lp and the voltage gain within the secondary circuit when driven at resonance is equal to its Q factor. Thus, the secondary Q should be as high as practical. Q factor IS a factor of the final gain product. That is, ignoring dynamic loading effects, a coil with a secondary circuit Q of 200 will have twice the voltage gain of a coil with a Q of 100.
No. The maximum voltage gain in a conventional Tesla coil, modeled as two coupled LC circuits, is given, by energy conservation, as que square root of the ratio between primary and secondary capacitances, or, equivalently, by the ratio between secondary and primary inductances. High Q in the coils can't increase this gain. Low Q can reduce it, of course.
I think I get what your saying. I certainly have a lot still to learn, but a lot of what I said above is actually consistent with what you're saying here.
So in a real world coil, what is a typical critical value, where the correlation stops? I could use some examples. What about slayer exiters? They often don't even include a primary cap, and basically just pump the secondary circuit continuously. Also, what about 3-coil TC's? Doesn't the tertiary circuit effectiveness depend on it having high Q?
Registered Member #1321
Joined: Sat Feb 16 2008, 03:22AM
Location:
Posts: 843
Maybe you are asking something like: Being that there is a Q dependent voltage gain possible with a series LC circuit, then is it somehow possible to get a very high voltage gain from a crystal (such as used in a crystal oscillator), which has a very high Q?
And I think an answer is no, because, when you look at a crystal equivalent circuit, you cannot get access to a set of terminals where there would be a voltage gain as in a discrete LC circuit.
Enceladus wrote ...
Ever since I leaned that Q values in excess of a million are possible with crystal resonators I have wondered if there might be a way to design a crystal power oscillator that would operate something like a Tesla coil with the conventional secondary circuit replaced or supplemented by a crystal with potentially several orders of magnitude greater Q factor. I've tried simulating a few schemes where I basically placed the crystal below and in series with the topload of a conventional coil with very underwhelming results. I know essentially how to simulate the behavior of a crystal but I'm still not grasping something here.
Can any of you think of any way this sort of thing could work? Is there even any merit to the idea?
Registered Member #39190
Joined: Sat Oct 26 2013, 09:15AM
Location: Boise National Forest
Posts: 65
Yup. It's a case of taking lumped parameter models too far. All models (as all analogies) fall apart at some point. But if anyone wanted to do some crazy experimentation, a large bar or disk of PZT might be a place to start.
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High Voltage Crystal Oscillator
