Hi to all
I have a ready to use tv flyback to create 20KV HV at 1mA. With this Transformer i will charge a cap through a charging coil and a de-q-ing diode.
According to the equations i found on this page http://www.richieburnett.co.uk/dcreschg.html
i calculated a huge inductance coil (Lp) and i don't know if i made a mistake on somewhere.
At the end of the page the last equation calculates Lp. I used as Vdc=20KV, Pmax=(20KV X 1mA)=20W, and BPSmax=500.
With these numbers i find an inductance of 8114H !!!! Is that possible???
TNKS
Jeg
What your numbers are telling you is what I think I told you some time ago: the flyback transformer does not supply enough current at the rated voltage to work effectively in a SGTC with a rotary break.
Instead of the flyback, put in a MOT at 2 kV, 600 mA, and see what you get.
Hi Tinsel thanks for the reply
I re-calculated inductance with the numbers you gave me, and finally became a normal value of 0.8H!
Ok. I will search a little for finding a good mosfet or igbt driver for my MOT and i ll be back again later.
tnks
Just plug the MOT into a Variac, you don't need a driver. Use another MOT primary in series, secondary shorted, to act as a current-limiting choke, or just be careful on your input current.
Quote from: TinselKoala on April 30, 2013, 12:58:31 AM
Use another MOT primary in series, secondary shorted
You mean to connect the second MOT in series with the secondary of the first MOT as a ballast? Is it still deadly dangerous even with this current limiter?
Sorry, no, you use the second MOT, with its secondary shorted, in series with the _primary_ of the main MOT. This is just like using a big choke on the input to limit the input current. MOTs are not current-limited the way flybacks are, so if your output impedance is low, it's easy to draw so much current in the primary that breakers trip or the smoke leaks out. SO you use the second MOT primary as an input choke, just to limit the inrush current when the discharged cap bank is looking like a direct short across the MOT output. Then downstream from the MOT on the HV side you put the FWB, and then the HV choke and de-Q diode if you are using them.
I don't have another MOT so on my coil I put an ammeter around the MOT input lead, after the Variac, and I watch the peak currents and don't let it go over 15 Amps. I've still managed to blow a couple of fuses in the Variac, though. Putting the second MOT primary in the circuit with its secondary shorted will prevent the input current from going much over 10 Amps and I should be able to run continuously without problems at that point, but first I have to find the second MOT !!
Hi Tinsel
If i put the second MOT as an HV choke in series with the secondary, will it also react as a current limiter? I ask because i will need a charging coil in the secondary anyway, so if it works as a current limiter i will save some space and some extra work!
What FWB stands for?
Jeg
Quote from: Jeg on April 30, 2013, 07:15:11 AM
Hi Tinsel
If i put the second MOT as an HV choke in series with the secondary, will it also react as a current limiter? I ask because i will need a charging coil in the secondary anyway, so if it works as a current limiter i will save some space and some extra work!
I don't know if it will work that way, but you can certainly try it, although I'd be a little worried about heat buildup. I've only heard about using the second MOT's primary in series with the mains supply to the working MOT, as I described above. But experiment, by all means... just be careful, the MOT is deadly.
Quote
What FWB stands for?
Jeg
Full-wave bridge. Made of HV high current diodes. In my MOT DC coil they are the black bell-shaped things to the left of the capacitor bank.
Quote from: Jeg on April 30, 2013, 07:15:11 AM
Hi Tinsel
If i put the second MOT as an HV choke in series with the secondary, will it also react as a current limiter? I ask because i will need a charging coil in the secondary anyway, so if it works as a current limiter i will save some space and some extra work!
What FWB stands for?
Jeg
Yeah you can do "secondary side current limiting". See the link. http://www.kronjaeger.com/hv/hv/src/mot/index.html.
The resonant charging circuit does that. http://www.richieburnett.co.uk/dcresist.html
I use a MOT secondary for the charging inductor in my resonant charging circuit. I also have a 400 mH choke made from 0.5 mm wire with removable core in series with the supply, the two "Supply" MOT primaries are in "anti" parallel then another MOT's secondary is the charging inductor (this MOT can have it's primary shorted to reduce it's inductance). The power is limited to about 650 Watts, current about 2.7 amps in my setup at full power, the HV caps are actually 14 nF, frequency 750 kHz or so.
FWBR means a Full Wave Bridge Rectifier. My circuit uses one but it's drawn in two parts. (https://overunityarchives.com/proxy.php?request=http%3A%2F%2Fi227.photobucket.com%2Falbums%2Fdd168%2FToey1%2FDualMOTPrimaryCircuit12.jpg&hash=b1609acd5dbbf70f9501170c0a32d00f0cc6d054) (http://s227.photobucket.com/user/Toey1/media/DualMOTPrimaryCircuit12.jpg.html)
Cheers.
P.S. I can calculate my power input by using the electronics assistant program to tell me the energy in the HV caps and multiply by the breaks per second.
Say I dump 8000 volts from a 14 nF cap 500 times a second, 0.448 Joules times 500 = 224 Watts. And it correlates with the energy meter with a bit of losses.
The MOT secondary charging inductor will only allow the supply to charge the caps at a certain rate so the input is limited that way.
Even 6000 volts into a one turn primary with 180 secondary and extra coil turns (combined) would give a transformation to 1 million volts. ;) Without any resonant rise.
My setup has one primary turn and about 200 turns in the secondary and extra coils combined.
Speaking of "Q" my secondary and extra coils combined have about 3 Ohms resistance and the top load is about 16 or 17 pF I think. And the setup has about 2.5 mH in the secondary and extra coils combined. Almost a Quality factor of 4000. http://www.circuitsage.com/tools/tool_view&tool_id=17
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Thanks, Farmhand, what you've described is indeed the "right" way to do a DC rotary SGTC using MOTs. Is this the coil that you showed in operation earlier? What happens when you let it pull 1500 Watts input, instead of limiting to 650?
I'm working on a zero budget so I have to design from what's on hand, rather than designing to theory and then building it with the right stuff.
I'm on a 115-120VAC main, so my 15A current input (manually limited) is equivalent to 7.5 A input in your 220-240 system. But I'm only using the one MOT so my output from the FWB is nowhere near the TC primary voltage that you are getting, I think.
Yes same coil, It's a fairly big one, not the smaller ones I sometimes use for experiments. It's a screamer, I had to go to 1500 BPS to get 650 Watts into it when the power levelled out. I'm not so confident to try more power just yet, I'm not sure all the components could take it. Because of the fairly high frequency the primary capacitance is small so for a fair sized coil that's not really enough I don't think. Can't use any less than one primary turn though. :)
The MOT's here have more primary inductance, 236 mH each, they vary a bit.
The supply MOT's are power factor corrected (almost) which helps for more output voltage, it took 39 UF to do it.
If each MOT makes 2000 volts and the two are adding voltage then the charging circuit gets 4000 volts to double. I have to set the safety gap pretty wide, about 7 mm.
My guess is if I just remove my ballast coil or replace it with one that has less resistance or inductance then it will be able to use more power. I should try it because it sounds like fun. When I short the primary of the MOT I use for the charging inductor the secondary reads 4.7 Henries. With the primary open it's over 20 Henries. I use it open.
Three MOTs makes the setup awkward to try to lift or move. The downside to MOT's. Speaking of using what is laying around, I made the rotary spark gap from wood and the rotor is cut from a "cutting board" plastic one. It's got a small universal motor from a floor polisher in it, with 50 volts DC it can do 6000 rpm and it has 8 shorting bars on it, It also has two breaks at 180 degrees so I can double the rate that way.
I'll crank it right up soon. I'll be needing a fix sooner or later.
Cheers
Hallo again.. :)
After the summer vacations i started again the HV Experiments!
Well, i have a mind trouble, so if anyone can guess a solution to my difficulties i will appreciate it!
So! I built a dc power supply using a MOT with 2 more mots as a ballast at the input. (I don't have a variac)
I used two microwave oven caps in series as a smoothing cap. So far so good. It gives me a 2.2KV DC Output as expected. Next stage is a de-Q-ing diode followed by a 4th mot as a charging coil, and 3 mot's caps in series as a tank cap. The problem is that it also gives me a 2.2KV output and not 4.4KV as expected! I tested the diode the coil and the Caps and everything seems to work right. Where is the mistake? The circuit is following...
You probably have way too much capacitance. Disconnect the three series MO caps and then see what the voltage is. Then use a capacitor that is properly sized for your primary coil.
My DC coil uses a single MOT and a single FWB, no de-Qing diode (I tried one but found no improvement) and about 160 nF total capacitance in the primary circuit, but I am also using a fixed 2-element spark gap with blown quenching.
Tinsel is correct, the final caps you have, have possibly around 330 nF which is a lot.
Also if you have too much ballast on the input then when the setup is loaded not enough current will flow
to properly charge the caps. Which is why I tune the MOT Primaries to resonance, or power factor correct them,
that makes the transformation solid with less voltage drop. With all the ballast in your primary circuit the inductance
might be too much, and the primary circuit may well be tuned to too low of a frequency, or if you are using the secondaries for ballast
to the primary of the MOT then the resistance will be way too much for the voltage applied. Three MOT primaries with no capacitors
should be ok and not tuned too low, I put the PFC caps directly across the MOT primary. There is some trial and error due to system particulars.
But if you use the primary coils of the other MOTs as input ballast it should be OK.
Try shorting the unused primary of your secondary side MOT which is the charging inductor. That will reduce the charging inductors inductance,
alternatively the small LV coil can be shorted. for less decrease in inductance.
If your primary has only 4 uH and the transformer frequency is, lets just say 400 kHz then you would only need
40 nF of final HV caps. If the primary coil had 12 uH and freq. is 400 Khz then you would only need 13.5 nF.
It's best to tune the primary a bit lower in frequency than the secondary oscillating circuit, because loading with streamers
lowers the secondary resonant freq.
Thanks guys! Your experience is really valuable and i appreciate it! :)
I was just hopping to avoid building an MMC bank, by using what i readily have. And what i have are 5 mots and 5 MO caps! Anyway, i hope the next days i will finish the supply and loading part of the system.
In the following pic you will see at the primary side a MO pcb which includes a line filter and a current limiter (via resistance and relay). But there is one more watt resistance of 3.3K, feeding a 24V zener for the relay pwr supply. And this resistance gets so hot that you can not touch it after some few seconds. Is that normal?
Tnks again
Hallo again. :)
I still get at point B the same value with point A.
Well, i tried with
1. no de-qing diode,
2. other MOT as charging coil, i tried with open/close primary coil of the charging trans.
3. Smaller Cap at the end (5nF)
I also tested without cap, and still the reading after the charging coil is 2,2KV. The same as at point A!!!!!
Do you think that i have to ground something at this schematic? I just grounded the PCB input Line filter and limiter! Nothing else!
Tnks
Are your bridge diodes working properly? What is the part number of the diode you are using?
My suggestion is to break it down by steps. Completely disconnect everything to the right of the main MOT. Leave the left side alone with the two MOTs as chokes, that is OK. Test the open-circuit voltage output of the main MOT. It will be AC... it had better be AC! Be careful here. What is your _rms_ voltage reading?
Now hook up the FWB only, and read its output. This should be "pulsed" DC at twice the line frequency and the peak voltage should be substantially higher than the AC rms reading. It would be excellent if you had a Variac, so that you could do both these tests at low input voltage first.
FWB consists of 24 X 4007 diodes. Each diode has a voltage rating up to 1000V.
I just tested it again by the help of an oscilloscope. FWB work as expected. A rectified signal at 100HZ. Capacitors smooth it at a decent level. RMS is 2,2KV. Then i connect the charging coil and the final capacitor and nothing changes!!! Nothing at all! Is there any possibility to need more inductance? I am thinking to try two mots at series as a charging coil. Any other ideas?
OK... so you've confirmed that the FWB may be working properly, under no load. It is not how I would have made the bridge -- I would have used higher current diodes and I am surprised yours are holding up, actually. You raise the voltage handling when you put them in series but the string can still only handle the current of a single diode, and the 4007 is rated at 1 amp continuous rectified current. I think in full operation these diodes will fail pretty quickly. May I suggest that you construct your bridge from heavier diodes? I recommend the sturdy workhorse 6A100 (data sheet attached below.) They cost under 50 cents US each, as low as 27 cents in single units from the right supplier, or as low as 17 dollars for 100 pieces.
(I am assuming you are using 6 in series for each leg of the bridge, but if you are using 2 parallel strings of 3 in series for each leg, that increases the current handling to 2 A but interesting things will start happening as diodes fail....)
I appreciate your answer but I still can't get the info I need.
1. What is the AC output, unloaded, with nothing attached, from the main MOT? AC rms please.
Now hook up the bridge, and nothing else.
2. What is the DC output, unloaded, with no filter or anything else on the output, from the FWB? Peak DC output, the max height of the ripples, please.
3. Now hook the filter capacitor only across the FWB output and measure the voltage again. This should be your "decently smoothed" DC level and it should be nearly the same as the max DC ripple height.
Now... as to what I would do... Personally I would forget the "theory" and dump everything to the right of the FWB and feed the unfiltered, unchoked output directly to the primary tank circuit. As I showed in my single-mot DC blown SG coil. I think this would work fairly well with a properly configured rotary gap and I know it would work great with a multiple-element air-quenched gap. Of course you will still need current-limiting on the input, so I would suggest buying a good Variac. They really are indispensable for this kind of working.
But that isn't helpful to you, I know. Let's see if we can get the readings I asked for above. There may be nothing wrong with the 2.2 kV reading you are getting, or we could be seeing an underperforming bridge, or a really leaky capacitor. So let's look at the voltages from the beginning.
Have you got your spark gap built? Can you give the details of what you intend to use for a gap?
Hi Jeg and Tinsel, It is strange that the charging circuit is not working, again Tinsel is correct, if the charging circuit is not working there must be a problem so disconnecting it might show where the problem is. I would take a picture of my primary circuit but it is quite busy under the coil and would be difficult to trace the wire's and bits. One problem with using a MOT for a charging inductor is that the secondary is connected to the core/body of the transformer so the entire MOT core is at HV, I had to raise mine up off the wood base and sit it on wax blocks otherwise it arced into the wooden base and lost power but still tried to work, the other option is to disconnect the end of the secondary connected to the core but I don't think that way is without problems.
I didn't get the the charging circuit working properly until I used the rotary spark gap so that I had a reliable break rate. Your kinda jumping in the deep end using a charging circuit in a medium powered transformer as a first attempt. The charging inductance is related to the break rate and the HV caps it charges. It's a "Dark Art" with few hard and fast rules. The best way to gauge output voltage is to setup the circuit without the charging inductor or the De-Q-ing diode but with a safety gap across the Power MOT secondary about 1.5 to 2 mm and set a small working gap but keep increasing it till it stops and the safety gap fires, then add the charging inductor and de-q-ing diode and see if the working gap fires, when you can get a 3 or 4 mm spark on the working gap but the safety gap stops firing and is smaller then you know the charging circuit is increasing the voltage to the HV discharge caps. The actual gap in the spark gaps needs to be adjusted to "conditions" there is no actual distance can be given only approximate.
Open circuiting a MOT can damage the insulation if high enough voltages are reached, safety gaps prevent that happening, but using only one MOT the gaps will fire from HV to ground which I don't like to do, my gaps go from HV positive to HV negative not to ground. Is it possible the MOT insulation is damaged and the inductor is not really being utilized.
The charging circuit needs to have a certain amount of inductance, it is a bit flexible and it can work without the de-Q-ing diode but won't work if the FWBR is kaput or if the charging coil is shorted internally, diodes do weird things and they can test OK but not work properly, these circuits are hell on some parts and at times momentary currents can get to ridiculously enormous magnitudes.
I can't even test a Microwave oven diode, my DMM just says it's open circuit, if it showed a short then the diode is busted, but in between open and shorted funny things can happen also.
I use Microwave oven diodes for the FWBR and then I use two microwave oven diodes in series for the "De-Q-ing" diode. I found when the charging inductance was not enough
the supply can drive the primary directly through the spark gap which seriously heats the FWBR diodes as well as other things and uses a lot of power.
Just now I am not prepared to use my coil, I'm right out of space and the ground is dry as can be, if I fire up the coil with no ground connected it rattles the sub woofer connected to my computer by way of signals through the built in amplifier in the speaker system. ;D I won't use it unless I get good ground conduction. It'll rain within the month.
Don't allow it to frustrate you, you'll get where your going if you remain safe. Safety first, fun second. ;)
Cheers
Tnks for the answers guys :)
Well, I measured it again step by step. The results are:
1. Main MOT unloaded AC Output: 5000V Peak to Peak (Oscilloscope) / 1460V AC RMS (Voltimeter)
2. FWB output without smoothing Cap: 2500V Peak to Peak / 1300V DC RMS
3. FWB output with smoothing Cap: 2120V RMS DC / ~200V p-p Ripple. (low Ripple peak 2000V, high Ripple peak 2200V)
About the diodes.
Tinsel, you are right about the 6 diodes leg of FWB. It handles 6000V 1A per leg.
I thought that the maximum current (shortcut current) of the main MOT secondary HV side, is not more than about 625mA! Is that wrong?
For a start as a spark gap i will use a car spark plug. I opened the tip around 4mm but i will fix it on its final position after getting the right 4,4KV at the output.
I will try today to locate the diodes that you proposed me. I hope that i 'll find them!
Farmhand thanks for the info. I just wonder about your FWB. Each leg will handle not more than about ~700mA/~12KV. Voltage margin is more than enough. But hat about the peak current?
Thanks Jeg for making the measurments again. It sounds like the basic DC power supply is working without major problems. I would still recommend going to a higher current diode than the 1n4007 though, because of heat dissipation and safety margin. The 6A100 is very common, you should have no problem finding them. But don't stop work while you are waiting, keep going with the "current" bridge, haha.
Next step is to put the de-Qing diode in. That is your MO diode, right?
I really don't think you will be happy using a simple automotive spark plug for your spark gap. I could be wrong, but I think it is likely that you will get a power arc across the gap instead of an interrupting spark. You could try blowing it with compressed air if it turns out that the power arc is a problem.
Here's a photo of a simple multi-element spark gap that might work better than a simple automotive spark plug. I would suggest using 4 tubes to start with, each screwed thru the center as shown, and positioned close together. The resulting gap can then be adjusted by turning the tubes around the screws, so that the tubes are still parallel but closer or further apart.
|||| furthest apart, or //// closer together, get the picture?
So the end tubes are connected to the circuit, the two middle tubes are "passive" and you have three spark regions.
http://www.coe.ufrj.br/~acmq/tesla/mres4gap.jpg
I'll be making one like this to try on my MOT-DC coil fairly soon.
This is very smart! Do you think that a pipe system doesn't need air blowing? What kind of metal is the best for sparks? I mean is there anything that last for a long time without getting black and carbonized?
And there is something else that i always wonder about. Are Tesla Coil discharges harmful? If a long spark from the top of Tesla coil find your hand will it harm you?
Quote from: Jeg on September 07, 2013, 03:08:00 PM
This is very smart! Do you think that a pipe system doesn't need air blowing? What kind of metal is the best for sparks? I mean is there anything that last for a long time without getting black and carbonized?
A good multi-element gap shouldn't need quenching with compressed air, but you still should have some ventilation. The sparks make nitrogen oxides from the air and this isn't good to breathe. Most people use copper pipe because it is cheap, available and easy to work with. You will have to clean the electrodes of any spark gap you build, even if you use tungsten or something like that, but it's easy enough to do.
Quote
And there is something else that i always wonder about. Are Tesla Coil discharges harmful? If a long spark from the top of Tesla coil find your hand will it harm you?
A properly running low power Tesla coil's output is a clean sine wave oscillation at a high frequency. This has two effects: First, the nervous system doesn't respond to high frequencies so you won't feel a "shock". Second, the power travels over the skin rather than penetrating deeply. This means that you can take the discharge safely, but NOT DIRECTLY TO THE SKIN because you will get a bad RF burn at the point of contact. However you can hold a wrench or screwdriver firmly in your hand and then let the spark go to the wrench first and then you won't feel it at all. This isn't harmful.... IF the coil is working properly. If there is a short to the primary supply, then DANGEROUS voltages at the low frequency of the mains supply can be mixed with the Tesla discharge and this is VERY dangerous. So for larger coils, for questionable builds or coils that might not be running perfectly... don't do it. I've gotten a couple of bad RF burns. Even small ones are very painful and take a long time to heal.
I used to do a demonstration with my big 2kW class traditional SGTC, with rotary gap and neon sign transformer primary supply. This coil would make a thick ropy arc 18 inches long into a big wrench that I held in one hand. My other hand held one terminal of a small 15-Watt 120V light bulb. I could touch the other terminal of the bulb to another person's skin and the filament would glow brightly.
I was a lot more confident and less careful in those days ! But it was actually fairly safe to do that.
The coil I show in the video below gave me a bad RF burn one day when I reached out and touched the secondary just above the primary winding. There is less than 100 volts DC being switched in the primary! I thought it would be OK to touch it so low on the secondary but I was wrong. It cooked a pea-sized chunk of meat in my finger, all the way to the bone, took weeks to heal and I still have the scar from it. Even just above the primary winding, the secondary was already making enough voltage to penetrate the insulation on the wire and there was enough power there to cook my finger instantly. I felt that, all right!
http://www.youtube.com/watch?v=UFHNY38GQsI (http://www.youtube.com/watch?v=UFHNY38GQsI)
This is an early demo of a low-power run of a solid-state TC. The boring stuff in the first five minutes can be ignored. I show some power arcs and wood burning to demonstrate that there is power and heat in the discharge, then I let it discharge into a small metal screwdriver that I'm holding.
I am not confident enough to try this with full power in my blown MOT-DC coil but I've done it with the SassyClassE SSTC.
And I would not recommend trying it on a MOT-powered coil, or ANY coil, unless you are absolutely sure of two things: It must be _impossible_ for any of the primary tank supply to be directly connected to the secondary output discharge in any way. You have to be very careful about this because the primary can spark to the secondary down low where you might not be able to see it and this can mix primary tank current into the secondary discharge. Second, make sure the coil's output is "clean", a sinusoidal oscillation at the resonant frequency with not much distortion or noise.
I don't recommend this at all, actually. If you do decide to take a Tesla Coil discharge into your body, even from a small coil, you are RISKING YOUR LIFE if something goes wrong, and MOT powered coils are especially dangerous because the MOT does not limit current in the same way that a NST does.
I agree a SG TC with a damped wave is nasty only a continuous wave transformer at HF is actually "really" safe.
You might see people do it on video and walk away but the long term effects they likely won't admit to.
It is a very good idea to start with low power solid state transformers.
Here is a clip of a 12 volt solid state continuous wave transformer, it burned holes in glass and fingers no problem with only about 600 volts on the terminal.
I originally kept this video private for a friend so I am relaxed and off guard. I show the voltage gradient, put a small hole in a neon which usually works better
than it did and qt 6:15 near the end I get a HF arc burn halfway up the extra coil.. :-[ It burned right through the tough skin on the end of my finger in about 0.5 of a second, it left a small crater so the skin was vaporized. I didn't see any smoke. ???
http://www.youtube.com/watch?v=4b4qzdBQgWg
..
Nice work guys and cool videos! HV is dangerous but so fascinating!
Well, i tried almost everything to double the voltage but nothing. The only thing i didn't try is to disconnect the input pcb which was taken from a microwave oven. It suppose to be just a line filter and an inrush current limiter! How can this affect the output? Anyway. I am thinking to built Farmhand's circuit for 8000V. Two mots input, middle ground output, and charging coil after rectification.
If i use copper for spark gap then what the color of the spark would be?
Well, i built Farmhand's circuit but again the same problem! L2 and L3 don't double the 5KV output of the two antiparallel input mots. I start to believe that the problem is the input pcb! Tomorrow i ll disconnect it and measure again.
Farmhand did you use mots for L2 and L3?
Tnks
Hi Jeg, L2 and L3 are just extra coils they aren't really necessary, L4 is the main charging inductor, it's the MOT secondary and the frame will be "hot" because it's in an active line. I just put the L2 and L3 coils there of a millihenry or few every bit helps I guess, as long as it's thick wire, that is because being less inductance they will not increase too much the voltage so mustn't waste power either. I think even MOT primaries would be too much, I don't even think my coils are 1 mH. Good job getting two in anti parallel anyway.
Now with the MOT for the charging coil, you can set it up on something that is a good insulator so it does not arc into the table and back to the supply/circuit ground, I had mine on a wood base that also had the power MOT's screwed onto it and the charging MOT arced into the wood which drained my power a lot. I had it screwed in to the base as well so I didn't see it until I tested it.
I wouldn't think the line filter would limit anything. Unless it's damaged maybe. Is it fused ? Try a different fuse maybe if it is.
Can you show a picture or a drawing of your circuit now ? Even the two MOT's in parallel should work a gap Ok but you'll want some restriction of current I agree.
One other thing is that with a charging circuit to get it going on a static gap it might be necessary to halve the spark gap distance because no doubling will occur until after the first cycle is finished maybe two cycles.
Tesla used a static spark gap with one electrode one electrode that was movable so he could tap an insulated extension of the electrode to "narrow the gap to start the process. With the rotary gap I can have a very small gap and it makes it work, I adjust it so that when the electrodes heat up the almost start to touch and sometimes do.
The less the gap the less the resistance of the gap. Another reason rotary gaps are good. But a static will work if the process is started somehow. If the gap is too narrow to start with and fixed so it works straight away the extra voltage would maybe cause power arcing in the gap
With a well setup air blown gap the gap can be small and blown after starting to prevent power arcs in the spark gap.
I hope we can help you sort this out. :)
..
Hi Farmhand :)
Arcing through wood??? Almost unbelievable! I will try a pcb under the mot. I hope this will give a good isolation.
About the drawing, it's the same with yours but with my input pcb which i will disconnect i hope today. I will change the topology again, and i will stick on one mot input and charging coil for 5KV. This is enough for me as i want to use it for gray's tube also.
After some tries to locate capacitors for the tank cap, i finally bought MKP caps (blue and yellow) 1600V each. I don't know if they are robust enough to handle all this charge/discharge thing, but it's a start. What type of caps do you use for that job?
Well, the filter line has a fuse but i didn't test it because power comes in and goes out from pcb, and i had guessed that was ok! I will do some tries today and i'll post again the results. Thanks for sharing your experience.