I have decided recently to try a few experiments involving high voltage, namely Avramenko's plug experiments. I need a transformer that can get me up into the 3-5kv range. Amperage is not really important at this point, im just looking for a high voltage transformer.

I have thought about winding my own, but dont want to invest in hundreds of careful turns of wire before I consult those more knowlegeable than myself.

First the perameters, the operating frequencies of the coil will be pulsed DC at 10khz or higher (definitly not into the Mhz range, closer to the 10khz side) Primary recieves the pulse, secondary needs to be in the 3-5kv range. For input I have a beast of a signal generator that will put out about 10.94 volts at 1 amp. I would like to drive it from this if possible, otherwise I will set up a mosfet driver to feed it, but I would like to use as little power as possible on the input. I chose mosfet, because I will be driving it in pulse mode, where quick on and off of the pulse are essential.

First I just tried to hook a bunch of transformers together. This worked for about two of them, then results just plain sucked. Why wont this work?

I thought of using a Flyback transformer. I opend up a large TV and found a surprisingly small flyback. There were like 15 or so leads comming out of it total, which surprised me (with my lack of modern tv electronics knowlege). Deciding to tear it appart to learn from it I found out they had enameled all of the wires which makes sense seeing that we are dealing with high voltage, and dont want Ionization or corona leaks.

Is it possible to find flybacks with only in input and an output? older tv's maybe?

Now I have a nice split barrium ferrite core with some spacers (for magnetic reluctance)

The core seems a little small to have TOOOOOOOOns of windings so im guessing that I will need very few windings for the primary, and alot of like 30 gauge for the secondary. BUT....in doing a few tests, I couldnt get readings off of any of the transformers I made with like 10 windings or so for the primary.

How many windings min do you need for a primary? does anybody have any design suggestions that can help me achieve my goal, or do I need too look down another path? Any help at all would be really apreciated.

I realize alot of people dont leave enough details, maybe I have left to many, but if you need more info on what Im trying to do, ill be more than happy to elaborate. Also, if you want an interesting read, look up avramenko's plug....one wire power transmision and longitudinal electric waves. harkens back to the good ol tesla days.

 

You could try the transformer in a microwave. They are very high voltage from what I understand. But watch out for that Cap! I have one, but have not been able to locate a non-Chinese data sheet for it. I am afraid to just plug it in without looking over the sheet first.

And microwaves have some great switches in them for the door sensors. (at least the one I took apart did).

 

Look here for flyback info: http://uzzors2k.googlepages.com/flybacktransformer

http://www.electro-tech-online.com/g...ctronics-chat/

Be careful with the microwave transformer.
If you shock yourself once in a while, when working on projects, dont use a microwave transformer. It is instant death at those high voltages, with the high current the transformer can provide.

 

I built the Avramenko experiment some time back with success. I used a 555 driving a 3055 transistor that drove a car ignition coil. Beautifully simple.
I suggest you not use a MOT (microwave oven transformer), the things are deadly with about 500mA @2kV. One wrong move and it's toast for you.
Anyway JLNlabs has the experiment and how to build it nicely laid out. The ignition coil puts out about 10-25kV, and all off 12V.

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The only constant is change.

 

If you NEED a real EHT transformer, have a look for a neon sign maker near you.. They have transformers potted and tested from 3KV upto about 25KV..

Or if you must play with ferrites and home made stuff, do a GOOGLE for solid state tesla coils (SSTC)..

The idea of pulsing your coil at over 10kHz is a good one.. Makes it MUCH safer, read up on the SSTC coil for info why this is so...

Have fun, but pay attention to personal safety!!!

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A train station is where a train stops...
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Solid state Tesla coils have to pulsed at the resonant frequency of the secondary coil. This is in the 100's kHz for a small coil.
Here is Naudins replication of the Avramenko experiment.
http://jnaudin.free.fr/html/afep01.htm
And for all the good SSTC designs, Steve Ward is the man.
http://www.stevehv.4hv.org/

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The only constant is change.

 

Yes, I was thinking about a microwave oven transformer as well.....but guys I told you I would be driving it with about 1 amp at 10 volts, I dont think that hooking up this to a oven transformer sudenly makes a death trap, lol, im not using mains power here, remember im trying to use as little input power as possible!!!

I think I might go to auto zone or somehting after work and pick up an ignition coil, see what happens.

Thanks for the input..I do have a question though.

Why is it not possible to hook up a few transformers in a row. What prevents this from working? I understand losses in transformers are around 5 percent or so, so with three hooked together I would expect losses of around 15 percent, but im seeing nothing out of the third transformer.

 

Oh and JL Naudin's website is probably the coolest site around for those who have not visited. I have spent alot of time on that site, and it has gotten me thinking alot!

Dont be quick to dismis many of his experiments as "cant work", he is very meticulous and suports all findings with data. Good stuff.

 

It's because you're feeding a high impedance to a low impedance, this overloads the previous transformer. You need to specifically design your transformers to put them in series.

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The old style ignition coils used in older vehicles or on farm tractors run from 12v and produce some pretty high tension output. Very simple to connect and energize.

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I have some ignition coils at work that I've played with for pulsed DC power. They are your best bet. This one is good:

http://www.msdignition.com/images/pn8202.gif

IIRC He makes it to 8-10kHz or so. They say 45kV but it really only does 15kV (personally measured).

Running these with 555 timers is tricky, because you want to cut off the FET as soon as the coil saturates. If you just run a 50/50 duty cycle at a given frequency you will be burning up a lot of power just to keep the coil charged (basically the current saturates and once that happens you need to turn off the FET).

At work I found the best way to do this was with a PIC that had some DIP switches to program it attached, the dip switches programmed 'on' and 'off' time for the FET separately. I scoped the coil output with a HV scope probe and determined how long at 12V it took to charge the coil fully. I then set the frequency by keeping that charge time constant and varying the off time of the FET driving waveform. That way you get max spark at any frequency with no I2R heating losses just to maintain that current through the coil. Run your PIC off a battery, optoisolate if from the FET, and twist your wires so you don't make an antenna that resets your pic Also you should swing by Mouser. They sell 29kV insulated wires. $40 for 25ft, and it is definitely something you will need. Spark plug wires would probably work too, don't know what they charge for those though.

Anyway, that's the best way to do it I think, but it's a lot more design effort than the simpler (and potentially just as good, just harder to tweak) 555 circuits. Also, don't plan on more than 8-10KHz out of any ignition coil. They're just not meant to run at those frequencies. Charge time is too high.

New style electronic neon sign ballasts will give you 20kHz-40kHz AC waveforms at 5-10kVRMS, but they have short and open circuit protection and aren't as easy to use as the old style 60Hz ones. They have to make a continous arc to stay on, if the arc breaks or doesn't form initially they go into protect mode and you have to turn them off and back on again.

 

Well I am clumsy sometimes, so maybe I should just scrap the microwave transformer for the copper wire. It must have at least a few pounds of copper to bring to a salvage company.

Just curious: What is the usual microwave transformer voltage?

 

Hmmm, good aproach to finding the saturation time and varying the dead time in between to get your frequency.

What about inductive kicks? It is known that when you first apply a current there is a kick that can be seen. This is known to degrade vacume tube diodes and triodes even when the heater is not on. The kick is also present on a fast switching off of the current. Speed of switching increases the effects.

Will these be amplified (in terms of voltage, not power of course) in the coil as well? what im askin is if I switch on the current super fast, will I see an extreemly high voltage pulse off of the secondary?

 

typically 2kv output and nothing to play around with considering the current rating... you'd be real lucky if you lived through an accidental shock from one and further more it would be a miracle if your body didn't suffer some ill effect from the shock. The weight in those xformers is primarily from the laminated steel core, and not so much from the windings as you would wish to believe. I'd much rather get zapped from an ignition coil... even today's modern automotive 100kv coils than from a microwave oven's transformer!

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DONT PEOPLE READ THE POSTS??? lol, sorry didnt mean to yell, but im driving it with no more than 10 watts total!!! I dont think a signal generator (unless hooked up to an amp) has the juice to kill almost anything! no mater what form you put it in, 10 volts and one amp can be pulled off with 6 or 7 AA batteries! I AM NOT USING MAINS POWER AS THE SUPPLY