Explain difference in Tesla pancake cioil and a regular pancake coil

[magnetman12003]

What electrical specs are different as far as voltage and current in a bifiliar wound  Tesla pancake coil and  a regular bifiliar wound  pancake coil. Assuming both wound coils are the same gauge wire and length.

[thx1138]

There is no difference. Tesla invented the bifilar pancake coil so a "regular" bifilar pancake coil is a Tesla bifilar pancake coil. Note also that the patent states the method can be used with coils other than pancake coils. It's the bifilar part that is important, not the physical layout of the coil. Note figure 1 in the patent. That is a non-bifilar pancake coil. I'm guessing he used the pancake coil in the patent because it was the simplest to illustrate.
https://teslauniverse.com/nikola-tesla/patents/us-patent-512340-coil-electro-magnets

The discovery wasn't so much about current and voltage but self-inductance. It enabled him to attain voltages in the millions of volts without being hampered by needing to attach a capacitance to the coil to reduce self inductance. From the patent: "In electric apparatus or systems in which alternating currents are employed the self-induction of the coils or conductors may, and, in fact, in many cases does operate disadvantageously by giving rise to false currents which often reduce what is known as the commercial efficiency of the apparatus composing the system or operate detrimentally in other respects. The effects of self-induction, above referred to, are known to be neutralized by proportioning to a proper degree the capacity of the circuit with relation to the self-induction and frequency of the currents. This has been accomplished heretofore by the use of condensers constructed and applied as separate instruments. My present invention has for its object to avoid the employment of condensers which are expensive, cumbersome and difficult to maintain in perfect condition, and to so construct the coils themselves as to accomplish the same ultimate object."

[conradelektro]

Look at my two videos, they explain the difference. Also read the video description:

https://www.youtube.com/watch?v=spQ9yLdb7v4

https://www.youtube.com/watch?v=fC84W0PIZoE

Self resonance frequency of monofilar coil about 9 MHz.
Self resonance frequency of bifilar coil about  4 MHz.

Self capacitance of monofilar pan cake coil 9 pF  -- calculated from 9 MHz and 34 µH
Self capacitance of bifilar pan cake coil 46 pF -- - calculated from 4 MHz and 34 µH

The inductance of the two coils (monofilar and bifilar) is about the same (34 µH), but the bifilar coil has a much higher self-capacitance.

As thy1138 says, Tesla wanted to have a higher self-capacitance (in the bifilar coil) in order to get rid of a capacitor. It was a money saving idea and nothing mythical. At Tesla's time capacitors were cumbersome and expensive.

Many people do not know that the inductance of a monifilar and a bifilar coil (of similar build, wire gauge, wire length and diameter) are about the same.

Greetings, Conrad

[Magneticitist]

as another user said, nothing.
that is of course unless you simply series your wires at one end unlike Tesla's patent then
there is a huge difference. Don't do that.

[conradelektro]

as another user said, nothing.
that is of course unless you simply series your wires at one end unlike Tesla's patent then
there is a huge difference. Don't do that.

If you stay away from the self-resonance frequency, there is no practical difference.

But if you wind a large bifilar coil with very many windings you will get quite a high self-capacitance which starts to matter in an LC-circuit. You have to add the self-capacitance to the C (capacitance) in the LC-circuit.

Usually (in coils with a moderate number of turns and of moderate size, as in my videos) the self-capacitance is very low and does not count much (in a bifilar and a monofilar coil). Therefore the self-capacitance of the coil can be ignored in a LC-circuit (C is very much higher than the self-capacitance of the coil).

But Tesla used very large coils with very many windings because he wanted rather low frequencies with a LC-circuit (in the KHz, not in the MHz) and could build a LC circuit without a capacitor. The self-capacitance of the enormous bifilar coil was enough.

Why was Tesla working with rather low frequencies? Because he used a mechanical rotating spark gap to generate the frequency (in the KHz). Nowadays one would use a transistor oscillating circuit (which is pure electronics an can go up to GHz).

Greetings, Conrad