can E-fields *affect* only ferrite core materials? how about powdered iron core?

I'm guessing any ferromagnetic material. The only real issue with powdered iron in this application is the relatively low permeability...which means it is harder to get a high L. Since delta L is a key here, you may find powdered iron a bit limiting.


I took our hipot tester in our lab and put a bit under 4kv on one of these ferrite rolls with cap plates inside and outside and a coil around it. Inductance didn't want to start changing until about 3.5kv, but it did appear to change by about 20%. I also tried a larger device we've built, but it didn't show any affect at about 4kv...which was the max I had available. That fits pretty well the papers I've read that talk about permeability changes in an E field. In those papers, they tend to toss around numbers like 8-18kv per cm. Cosmo said 4kv, but that is overly simplistic...it is really a function of voltage per cm...not absolute voltage.

I guess this core of mine is useless? got the torroids from dead PC PS....

inner dia = 13.5mm
outer dia =  19mm
total of 8 pcs

But the relation to E-fields is new to me, do you have a reference to a paper ?

I just arrived at the conclusion from Cosmo's references to bifilar coils (which are really just wire wound capacitive plates) and Tiger's design which used foil plates, that this was a E field gradiant causing a saturation effect. Then I did a bit of searching on the net tonight for electrostatic effects on the permeability of ferrite and was very surprised to find many papers talk about that effect.

I'm sorry...typing this on my phone so I really don't have access to the links I was looking at earlier. If you will google "electric field reduce ferrite permeability" you should get several hits on papers that reference the effect.

I noticed one paper that talked about a 36% reduction in permeability at 5kv per cm. That agrees very well with what I saw in our lab and very well with Cosmo's suggestion of 4kv. Depending on the thickness of your ferrite, you may need more or less. A 20% reduction would be more than enough if your coil had enough inductance to start with, but you may need 100mH or so if the reduction in permeability is low. With higher excitation voltage you can get away with far less inductance.

@Ltbolo

I think we are up to something here.. ok lets consider an resonant? LC tank... assuming we use a ferrite torroid(Stacked to form a "tube") and a slit metal plate at the inner and outer sections forming a cap ....maybe in the 1nF range , depending on "thickness" of the ferrite, the thinner the more capacitance we get.... and vice versa... what do you suppose the L will be in here? the *bifilar* perhaps? or load coil?

im still trying to figure it out...

maybe a *new* type of experiment... since I don't have access to ferrite torriods, maybe an 8mm ferrite rod will do... 1st later is foil(1 side as cap), then 2nd layer will be coil(forming as an insulator), then sandwiched by another foil (now acting as other side of cap)...

what do you think...

Close. The copper plates form the HV cap, yes. Not sure whether they can be resonant or must be pulsed. Gut tells me resonant may be fine.

The output circuit must be tuned to 1/2 the HV frequency...no diode though...just a resonant tank. No phase adjustment necessary or possible.

Thanks for the search string, it led me directly to the paper you mentioned :-)

Yes, this is a parametric oscillation, so having the frequencies right it will spin up on its own.

The two resonance frequencies can be determined this way:
1. with no output coil cap mounted, the HV resonance is tuned.
2. with no HV tank exitation, an extra short exitation coil upon the output coil just for the tuning of the output resonance are wound.
This coil is exited with exactly 1/2 the HV tank frequency.
cap(s) are mounted until perfect resonance is achieved.

If you get it right, the output will ring up on its own from stray currents...like an oscillator circuit. Without some kind of nonlinear load like a light bulb, it will run away.

This is why I mentioned "adjusting the phase".

Have a look at it this way:
1. If HV exited at the correct frequency, it will run away with a linear load.
2. If the HV frequency is skewed sufficiently off twice the output resonance frequency, the output is zero.
3. If we monitor the output voltage as a parameter to control, and we have a phase comperator comparing the phase difference between the HV and output oscillation, then the output power can be controlled by controlling the phase difference. The two frequencies on average keep the relation Fout = 2 * Fhv, but by introducing a small HV frequency jitter, the phase difference is controlled.
4. Low HV means high permeability, high HV means low permeability if I got it right.
5. To increase output power the HV is high while the output voltage rises, and low while it falls.
6. To decrease the output power, the HV is low while the output voltage rises, and high while it falls.
7. Whether you have situation 5 or 6 depends on the phase relation, so a phase locked loop (corrected for the 2 factor) can control the phase so the output voltage is at a constant amplitude

Getting this far, the output coil can be harvested simply by closing a switch once the desired output voltage is achieved.

Or

Using Hectors diode plug, the energy are harvested non-linearly and non-reflective. This should allow more power from the same size core, at the cost of a bit more complex circuit.

I have previously posted my diode plug circuit here:
http://www.overunity.com/index.php?topic=8597.690
See from post #695 to #697.

On #697 the rightmost part of the diagram is exactly what I'm thinking of for the output coil. The exiting part and the feedbach need minor changes, like e.g. replacing the middle coil with a HV transformer with a tank circuit on the secondary for doing the HV excitation of the sliced copper tubes encasing the toroid cores.

The Q of the output circuit must be high enough to keep the loss lower than the gain. At high freq, Q can be pretty low...but the lower the frequency, the higher the Q must be to get it to light.

Let me say this...we have done this mechanically before, with a rotating I core piece to change the inductance of a U shaped inductor. It works...and it is feakin cool to watch. When you hit the right freq it roars to life...and literally roared...it was quite loud. The mechanical approach cannot be OU however. I do believe that the E field approach can be, since the E field may not consume energy while causing the parameter change.

Maybe you could use Hectors diode plug here also, it harvests "virtual power"

Thank you for sharing your ideas, the control of magnetic permability with an E-field must be a winner :-)

Eric

what do you suppose the L will be in here? the *bifilar* perhaps? or load coil?

We aren't planning to drive the excitation resonantly, so I haven't thought about it. You will definitely be using a transformer to step up the HV excitation, so the secondary would likely be very high inductance, perhaps even more than you want. That could certainly be used to tune resonance, but it may be a chore. As far as bifilar, when Cosmo talks about using bifilars, I am pretty sure he is using them as the cap plate instead of a solid copper or aluminum.

I have been thinking and experimenting with the concept of pulsing a coil at low inductance and collapsing it at higher one this may be a way of getting OU in a system.

That's backwards. Raise the current at high inductance and lower the inductance...the current goes up. Doing that in reverse eats power rather than produces it.

Of course, the manipulation of a PM field is not free or even efficient. What you put is what you get from it. I have experience in MEG setups, measurements taken and can say it with confidence.

You can't get OU from manipulating a magnetic field with a magnetic field. I suspect that the MEG does work...but...the control coils have to be very high voltage and should be using an electrostatic field to manipulate the PM field...not another magnetic field. The control coil might even work best as a bifilar...but I might be more inclined to use a pair of capacitive plates on the side of the core.

Do we have any concrete evidence Ltbolo, that E-field alters the magnetic permeatability hence inductance of a coil over a ferrite core? If yes, then we are on a good way i guess.

Yes. The papers I was referencing before are about doing exactly that.

But bear in mind, that plain inductance manipulation is not enough.

I disagree. The mechanical version we built was nothing but a coil and a cap. The coil had a variable inductance by way of a rotating core piece. With nothing but a variable inductance you can make big power.

Playing with solenoid out of ferrite, i could perceive one thing.

An air coil would have its inductance increased normally by putting it to core. (naturally)

If a smaller coil is made and inserted to the solenoid ferrite core then its inductance increases but it counts only as a single turn or just as a single wire going through the hole, no matter how many turns the insterted coil is.

No to mentioned that if both coils are placed on the same ferrite core, one on it and the other through it, do not interact while working.
It seems that the top coil creates a b-flux in parallel to the solenoid whereas the inside coil creates a flux perpedicular to solenoid's axis.

Going this a bit more far, i suppose the ferrite particles could sustain same time 2 B-flux vectors perpedicular to each other.