Body
MickWhen I get to it, I have some " Sprague
Energy Storage Capacitors". They are100uf 4000 volt units, and a bunch of Varian 2.5 uf 10,000 volt caps for tuning.I have been following Sven, but I see that you too are quite close, researching aother angle.Mohamed in Algeria got me on to making capacitors from aluminium foil and heavy construction polyethylene sheet which I have built and tested to 10,000 volts using an oil furnace ignitor transformer. They are easy to make fairly good quality capacitors this way.They don't suffer flash over through the poly, which surprised me.Don't expect them to be micro miniature, but they work just fine.I think I posted his book to the files, but then, I can't see files. I printed hard copy for myself.With all this political upheaval, we lost touch through the Internet.We also investigated powdered iron cores which were promising until the availability of Metglas, here in Canada, made it usable. Hitachi now owns Metglas, and will sell it.Who knows what will be helpful to each other? All we can do is to give it a try.Cheers WarrenSent from Yahoo Mail on Android
On Sun, May 6, 2018 at 7:51 PM, Mick [email protected] [EVGRAY]<[email protected]> wrote:
Hi Ole,
All great points, still thinking about ways of harvest as calcs will get close but there is always the gnats ass final nudge. Have not decided on the caps being filled quickly through loose coupling like a spark gap or power corection into a step down transformer,
Just the capacitance coupling of me being nearby changes things so I can see what Hector said about tuning is a bitch. Nice info on the flyback time transfer function.
I am trying to use distance as my answer the the capacitive coupling.
Yes your right it could be an avalanche punching through the gate would look the same as the ferroresonance, using an IGBT but same potential problem.
I would like to use a snubber without rounding off the corners of my square wave but this may also stop the coil ringing which is what I want.
Is a snubber cap any different than the same rated polycap?
Working in the major investigative stage now so all your points a very welcome!
On 5/6/2018 10:32 AM, [email protected] [EVGRAY] wrote:
Hi Mick,
The resonant frequency is given by the circuit parameters. If the iron core saturates most of the inductance vanishes which increases the resonant frequency. How fast the coil is demagnetized determines the peak voltage of the flyback pulse at a given current and inductance. The product of the voltage and time is the same for the input and output pulses when the circuit parameters aren't changed. Thus an output pulse of one tenth the length of the input pulse gives ten times as high peak voltage of the flyback pulse. The secondary then transforms that voltage by the ratio of the number of turns between the primary and secondary coils. For a tesla coil this ratio has to be calculated like for a transmission line transformer. I don't think transmission line theory is strictly necessary for calculating the output voltage of an iron cored induction coil. Use the formulas for normal transformers. A capacitor is placed across the switch to limit the flyback voltage peak to a safe value for the switch. If using a power MOSFETs as switch the MOSFET probably goes into avalanche mode without this snubber capacitor. A mechanical switch will just arc across the contact points without the capacitor. What is seen as ferro resonance could be an avalanche (breakdown) through the MOSFET. This happens very fast just like ferro resonance. It may degrade the MOSFET to give it a shorter life.
How fast the coil can be demagnetized depends on its parasitic capacitance and the load of the coil. A totally open circuited coil without any capacitance will demagnetize immediately and thus induce an infinitely high voltage. Such ideal coils doesn't exist as even vacuum has a dielectric constant. Thus parasitic capacitance is formed between neighboring turns which dampens the voltage. I.e. the energy is converted from magnetic field energy to electric field energy.
The induced high voltage of the secondary coil creates an electric field between the output terminals. If close to the earth or any metal parts the field will charge those parts even through a vacuum. If the distance isn't great enough the field will punch through and discharge the field. Else the energy is stored as an electric field around the coil and in the dielectric material between the windings. When the windings share a common connection between the primary and secondary coils the electric field has to be stored on the outside of the induction coil. Metal parts close by may get charged and discharge to the air by ionization or to persons touching them. Thus be careful when experimenting with high voltages. Everything is coupled by the capacitance between them.
Regards
Ole
---In [email protected], <mkjekyll@...> wrote :
Warren,
The earth spike seems to work weather or not there is a ferroresonance signature on the coil waveforme, just a whole lot better when there is.
Therefore the frequency become speculative as to what resonance one is working with, be in the spark gap or the modulation or the beat frequencies.
I think a wideband approach of filling some caps from a spark gap or plasma tube as fast as they can be discharged is the ticket. This is where the experiment becomes costly as the high voltage multi mF caps are not cheap.
In the Colorado notes Tesla has an extra coil in his Magnifying transmitter that no one seems to understand what he was doing with it. I propose this is the ferroresonant modulator.
A less costly way to harves is by PF correcting the energy to work in a transformer so the field requires much research and moving slow in order not to burn up parts
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