Some tests on mono and bifilar coils

[Farmhand]

It's very important to mention a familiar theme:  If you are playing with the coils in their self-resonant mode, there may be observable differences but the whole operation at that frequency is out of the practical usable frequency range for the coil.  Is there any practical application for a bifilar (or monofilar) coil in self resonance?  Can you do anything with it?  I know it's the question that some people hate, but it's a perfectly valid question.

MileHigh

This is the fatal drawback of the speed up under load effect in my opinion, and the point I try to make often. Using the coils at a frequency over their capability to output much power due to the restriction brought about by doing so, is kinda counter productive because it also make a high input with no load as well as a reduced possible output.

It is well explained in that MIT lecture on inductance I keep linking. he shows a table, the coil begins to act like a filter. I think.

Thanes video's show clearly the restricted output because his lights don;t light right up, the generator coils can't power them due to the current restrictions induced by the higher frequencies. But it does increase the input with no load, and when a load is placed on the coils while they are over their frequency capabilities doing so "unloads" the prime mover and the speed up occurs.

The series connected bifilar coils do have their uses, as Tesla states in the patent, but that is not the point of this thread MileHigh is it. 

Cheers

[MileHigh]

Conrad:

>>>To see the increased voltage potential between adjacent wires I have to lead out two adjacent wires?

For the bifilar you lead out two adjacent wires and for the monofilar you lead out one wire only.

>>>In the monofilar coil, a loop of wire from two consecutive turns?

As shown in the diagram, you just lead out one wire.

>>> In the bifilar coil, a loop of wire from the pair of wires?

Yes.

Going back to the frequency domain, lets say for a suggested test you connect your signal generator to a 50-ohm series resistor and then connect that across the coil.  As you sweep up in frequency the AC impedance of the coil will increase.  So more and more of the voltage drop will appear across the coil as the frequency increases.  You can try different resistors.  In all likelihood you will observe the same behaviour for both coils.  When you get to very high frequencies, you may start to see slight differences between the coils.

This is a basic bare-bones test that looks at the frequency response of the two coils.  That's dependent on the inductance of the two coils and since we know that the inductance is the same therefore the frequency response characteristics should be the same.

Permit me to take the stage for a second:  Now is a golden opportunity for someone to suggest some test and/or application that exploits the slightly larger tiny capacitance that has a higher potential difference between the two half-coils of the bifilar coil.  I am talking a real test that can be explained with sufficient clarity that Conrad can consider doing.

MileHigh

[MileHigh]

Farmhand:

With respect to the patent we have a disagreement.  I say that the patent describes the properties of the coil but it does not describe any use for the coil.  For example, to say that the coil can act like a series LC resonator, but it is not a "use."

There is no reason for disagreement really.  We both agree what the patent fundamentally says.  I am sure there are many patents for things that are more akin to explaining the properties of something as opposed to stating a practical use.

Interestingly enough, I still don't think I have seen a clip where someone shows a series LC self resonant mode for a coil.  However, Gyula made reference to it and said it can be found by frequency sweeping.

MileHigh

[MileHigh]

As far as filters go, a series LC circuit is a what's called a band-pass filter.   It lets a certain range of frequencies pass power from the input to the output:

(signal source) -> (series LC) -> load resistor -> Gnd.

A parallel LC circuit in the same setup is called a notch filter because it prevents a certain range of frequencies from passing power from the input to the output, i.e."the notch."

(signal source) -> (parallel LC) -> load resistor -> Gnd.

If you know the impedances of series LC and parallel LC circuits at resonance it should all make sense.

[conradelektro]

@Farmhand: thank you for drawing my attention to your coil winding video, the bee wax paper is a good idea. I use a home made winder, see the attached photo.

@MileHigh: thank you for taking the time to explain the tap loops. One could say that it is trivial, but only after one has read your nice explanation. So often the most simple concepts lead to misunderstandings (at least I have that problem).

Greetings, Conrad