Tesla pancake coil

[dmonarch]

I was wondering if anyone could explain to me the reasons for the design of tesla's pancake coil. The one made up of two wire side by side with the inner being fed back out to the outer.

Thanks

[chemelec]

You Might read This:

Tesla-Patent

[gyula]

I was wondering if anyone could explain to me the reasons for the design of tesla's pancake coil. The one made up of two wire side by side with the inner being fed back out to the outer.

Thanks

Hi,

By guiding the two insulated conductors and connecting them the way he described he received a so called distributed simple reactive network, a passive one pole if you like which had selective properties at a frequency (or probably at more frequencies).

The selective property means a series resonant behavior like a series LC circuit exhibits: there is a very low AC impedance at one frequency between the indicated wire endings. If you feed this coil pair at its endings with the same frequency current like the resonant series frequency then you find your current will see no other opposition than that of (the coils) ohmic resistance, or, in other words, as though it possessed no self-induction.
(words in italics are from his patent)

That is the important point.

rgds, Gyula

[dmonarch]

Wow

Wow thats some powerful property I had no idea. Thankyou

[wrtner]

or, in other words, as though it possessed no self-induction.

Does this mean that it will contribute nothing when trying to
achieve resonance if connected to an AC driven L or C circuit?

I am thinking of the people putting a pancake coil on an Induction
cooking ring. - Jean Naudin etc., and elsewhere here:
http://www.energeticforum.com/renewa...ilar-coil.html

[gyula]

Does this mean that it will contribute nothing when trying to
achieve resonance if connected to an AC driven L or C circuit?

I am thinking of the people putting a pancake coil on an Induction
cooking ring. - Jean Naudin etc., and elsewhere here:
http://www.energeticforum.com/renewa...ilar-coil.html

No I do not think it means that. Tesla did not imply that at resonance the pancake winding would not contribute anything, perhaps just the contrary...

By the way I have not seen (up to day) Naudin or others have tried to TUNE the pancake coil (they use) onto the output frequency of the induction cooker to achieve resonance.

Gyula

[We.The.People]

Another point about this technique I didn't see mentioned,
and Tesla was known to indicate this in patents,
is the result that occurs with fast pulsed DC.

With a standard winding, the voltage potential between a winding,
and the winding next to it on either side, is fairly a small potential.

By re-winding a second winding set next to the first windings,
the potential difference between all windings is now maintained
and a consistant, and great potential instead.

If the pulse is 300-Volts, the potential between windings is ~150-Volts.

His attempts to build better and better switching methods
to provide the shortest pulse of DC (NOT AC) that he could,
while breaking the flow before current could start was his goal.

Not to make a resonant "network" that balances on AC...

But gyula is dead right still though,
Tesla tailored his disrupters repitition rate
to achieve the very same outcome described.

His source was not AC though, just DC he pulsed.

They both can react in a "Pancake" as a standing wave.

[wrtner]

By the way I have not seen (up to day) Naudin or others have tried to TUNE the pancake coil (they use) onto the output frequency of the induction cooker to achieve resonance.

Gyula

They may not have mentioned, but I would have thought that they
would do that.

If so, how is the pancake coil considered, viz-a-ivz inductance
and capacitance?

Or is it down to trial and error?

Paul-R

[boguslaw]

Hi,

By guiding the two insulated conductors and connecting them the way he described he received a so called distributed simple reactive network, a passive one pole if you like which had selective properties at a frequency (or probably at more frequencies).

The selective property means a series resonant behavior like a series LC circuit exhibits: there is a very low AC impedance at one frequency between the indicated wire endings. If you feed this coil pair at its endings with the same frequency current like the resonant series frequency then you find your current will see no other opposition than that of (the coils) ohmic resistance, or, in other words, as though it possessed no self-induction.
(words in italics are from his patent)

That is the important point.

rgds, Gyula

Still trying to grasp the idea How to compute that frequency ? On which it can be dependent ?

[vrand]

Does this mean that it will contribute nothing when trying to
achieve resonance if connected to an AC driven L or C circuit?

I am thinking of the people putting a pancake coil on an Induction
cooking ring. - Jean Naudin etc., and elsewhere here:
http://www.energeticforum.com/renewa...ilar-coil.html

JLN is claiming output energy > than input energy, COP = 2.8

What about placing another output pancake coil on the other side of the cooker pancake coil? 2X more output?

cheers

[gyula]

They may not have mentioned, but I would have thought that they
would do that.

If so, how is the pancake coil considered, viz-a-ivz inductance
and capacitance?

Or is it down to trial and error?

Paul-R

Hi Paul-R,

Unfortunately, it can only be considered as a distributed passive network consisting of many small inductances and capacitors (and of many small resistances representing copper and dielectric losses). I think if you consider an equivalent circuit of a coaxial cable or a twisted wire pair (i.e. basically transmission lines) and start examining what factors influence the electrical capacitance between the two conductors, then you could have a starting point. And yes, after some theoritical approch like that it is down to trial and error. See my answer to boguslaw below too.

Gyula

[gyula]

Still trying to grasp the idea How to compute that frequency ? On which it can be dependent ?

Hi Boguslaw,

I am not aware of any, directly usable formula on your question, unfortunately.
However we can do some educated guesses. I believe first you wish to find means of increasing the electrical capacitance between the two parallel wires, just because normally in a distributed element network like this pancake coil, the higher the resultant capacitance, the lower the resonant frequency should be (this is valid for the resulting inductance too).
Now how can you increase capacitance between two parallel guided wires? One method is simply twist them together (provided at least one of them is electrically insulated. However, using normal enamelled copper wires with circular cross section seems to be the poorest choice in this respect because the facing surfaces which basically define capacitance are at a minimum for round wires. So you may wish to use insulated wires with rectangular cross section because in that case the facing surfaces can always be very close and parallel with each other. As an alternative, you may wish to consider copper foil tapes too (HomeDepot?), with insulation on one side of course. The insulation material on the surface of the conductors must have good HV properties, together with as high dielectric constant as possible, to further enhance the capacitance.

Armed with these considerations there may come some tests, after building a Tesla bifilar pancake coil from rectangular wires or from copper tapes and connecting the ends as shown by Tesla in his patent (Coil for electromagnets), you could insert the two connections of such a coil assembly into an oscillator to determine the resonant frequency, for oscillator I suggest a negative resistance one (because it is very simple) like a Lambda diode can give (member Lamare already showed such oscillator on this forum but it is on the web too). Once you have a good hands on first experience on such "flat" coils's resonant frequency from the measured oscillator frequency, then you can make further steps to bring that frequency down to that of the induction cooker. I say for the frequency to bring it down because I I think that those bifilar pancake coils Naudin, woopy et al has been using have a resonant frequency in the Megahertz range while the cookers work from the some ten Kilohertz to maybe some hundred Kilohertz frequencies. One notice here is in order: I believe when the bifilar pancake coil has the same resonant frequency like the cooker work with and you bring it to as close as is shown in the videoes then the mutual coupling AT RESONANCE may influence the normal workings of the cooker (because at resonant coupling energy transfer is much higher than at a non resonant coupling so far achieved) and the cooker may become very sensitive and unstable in its normal operation.

Gyula

[tika]

A tought about tesla bifial efficiency.

I originally posted this in the Gegene forum, but it belongs here more, methink.

This is just my take on this. Anyone care to comment ?

Electrically, the coil can be seen as a parallel RLC circuit:

---------+--------+--------+
         |        |        |
         /        S      ____
     R   \   L    S      ____   C
         /        S        |
         |        |        |
---------+--------+--------+

Note that contrary to a series RLC circuit, this arrangement will show a peak in impedance at its resonance frequency. This is due to the dual relationship of electrical circuits, which causes the effects measured on voltages in series circuit to be measured in the currents of the corresponding parallel circuit.

In the series circuit, large voltages spikes can be measured across the coil and across the cap when the circuit is fed an AC voltage. Which means that
in the parallel circuit large currents spikes will exist in the LC loop. Large current in the coil will bring about a very strong magnetic field. This oscillatory current and its induced magnetic field will peak at the resonant frequency, where impedance is at its highest, and thus input power is at the lowest possible for the circuit. Free real power!

It is impossible to measure current inside a bifilar coil, as this is happening on the entire length of the spires. But there is no radiant energy or 4th dimension magical vortex here. Just down to earth great engineering, like all of Tesla's inventions.

Hope this will help understand better why we are seeing this excess power and how we can get even more out of it. I predict that will be at the resonant frequency for the coil.

Source:

RLC circuit - Wikipedia, the free encyclopedia