Bifilar pancake coil overunity experiment

[gyulasun]

Hi F6FLT,

Okay on your monofilar coil and not a bifilar one.

The reason I believed you had referred to a bifilar coil was because you wrote this in your Reply 135:

...
According to a measurement of a second coil of 55nF, bifilar this one, with copper strips 5 mm width, I estimate the capacitance of the first one in the photo, 1.5 cm width and tighter turns, to be more than 200nF.
...

Anyway, no problem.

I would suggest two measurement methods to arrive at your coil's self capacitance value. One is described here in Answer 6, scroll down to about the middle: https://forum.allaboutcircuits.com/threads/measure-capacitance-in-a-coil-of-wire.8660/   
I think in that measurement method capacitor C2 should have a lower value than C1.  So you need say at least a C2=100 nF and say C1=220 nF good quality capacitor for such measurements. Of course, lower values at hand would also do.

The second method can be derived from this interesting current amplifying resonant circuit shown here:
https://www.accelinstruments.com/Applications/WaveformAmp/Magnetic-Field-Generator.html   (this paper was already mentioned in this forum and at other forum I think)
This paper can also be found here:
https://www.electronicdesign.com/analog/resonant-circuit-generates-high-frequency-magnetic-field

I mean that in the circuit shown in Figure 4, capacitor Cp would be the self capacitance of your monofilar (or bifilar) coil which gives the 1.5 MHz parallel resonance as you already measured.  And capacitor Cs should be chosen so that you get a series resonance with it when the generator is set to 0.707 x 1.5 MHZ = 1.06 MHz frequency.  And the value of the Cs capacitor when it series resonates your coil at 1.06 MHz will be equal to the self capacitance of the coil.
Maybe this method is harder to use because one would need a capacitor box adjustable in the some 10 nF values in some nF steps.

Gyula

[gyulasun]

Gyulasun, as much as i understand, this was, a pulse from the signal generator, through the coil, there was a resistor in series with the coil, and the voltage was measured on that resistor. Like on the figure below i guess. So it seems to be, like resistance was charged, then when the pulse ended, it discharged. But i'm not sure whether i understood rightly. What i asked was, in the end of the negative part of the signal, there is some ringing, waving or such, i ask whether this was caused by the coil.

....

Hi ayeaye,
Thanks for making the schematic for the F6FLT coil setup, that is also how I imagined. 

Regarding your question on the negative part of the output waveform, it should come from the resonant LC circuit behaviour when the self capacitance part of the coil charges back current with an opposite polarity and the coil will have an opposite magnetic field like earlier, a normal LC resonant tank circuit behavior takes place: magnetic and electric energy changes back and forth.  No matter whether you have a distributed capacitance or inductance like in a transmission line or in such flat strip wound coils or you have a normal lumped element LC components.  And even if there is no direct resonance between the input pulse frequency and the LC circuit resonant frequency, the energy ping-pong is able to happen to a certain degree, hence a negative voltage can appear too.

Gyula

[ayeaye]

This Trinket Python shell, it's a kind of weird, but it's a good thing. You make changes, run, even go back to that page later, and the changes are there. Yet after some time, the changes are gone, and it's back again as it previously were.

The only way to make the changes permanent, is to make changes, and then fork.

I saw no easy way to get an empty Python shell to play with, so the following is the one that i made. Fork it, then change it, then fork it again.

https://trinket.io/python/ab5dff2b29

There are two ways, a convenient way, and a way that always works. The following is how to go through two input files. You can likely figure out how to modify it, to go through whatever number of files. There is one more thing though. Like len(s1) < 2, if the length of the line that we just read from file, is less than 2, right? Trinket always has only one character, line feed, at the end of the line. Now if we don't want empty line, we end reading the file when the length < 2. But if we read like an svg file, it can have empty lines in it, and we should only end when the length is < 1. I hope this was not too difficult to understand, if anyone reads at all.

f1 = open("input1.txt")
f2 = open("input2.txt")
while (True):
    s1 = f1.readline()
    s2 = f2.readline()
    if (len(s1) < 2 or len(s2) < 2): break
    #Your code goes here
f1.close()
f2.close()

The following are the scripts how they should be, i didn't make the changes in the previous ones permanent i think, though they too work.

Input part calculation.

https://trinket.io/python/93b0840917

Output part calculation.

https://trinket.io/python/7b498b9a8c

[ayeaye]

a normal LC resonant tank circuit behavior takes place

Yes that was all that i said. As in the F6FLT's last test, the negative part of the waveform was due to the capacitance, the capacitance discharging when the signal generator output went to zero. But i said that we see some waving in the negative part, and this i think was due to this equivalent LC circuit oscillating. Which was maybe the only way how the coil's inductance revealed itself in that waveform.

How the capacitive coil is different from an ordinary LC circuit, is that current doesn't have to go through all the coil for induction to start in some part of the coil. But it may also mean that the current doesn't have to go all the way through the coil to charge the capacitance by induction, and the less current through the coil, the less lenz effect there may be.

There is always input and output part. And it is determined by whether there is any external supply of power or not. Like in the circuit that F6FLT used, when the output of the signal generator is greater than zero, a power is supplied to the coil and its capacitance, and this is the input part. But when the signal generator pulse ends, the signal generator becomes like connected to the circuit ground, and all the power in that circuit then comes only from the coil and its capacitance. Thus this is the output part. There is overunity when more energy is generated during the output part by the coil and its capacitance, than consumed by the coil during the input part.

F6FLT, please increase the resistor a lot, you waste terribly lot of energy, by the calculations i made that's insane. I guess the resistor should also be such that it fills the coil's capacitance in any observable time, otherwise there is too much input energy, and it kind of floods it. Oh wait, the time constant to charge the capacitance 63%, is RC, which in your case is 47 * 200 = 9400 nanoseconds, that is 9.4 us, which is a lot greater than your 16 ns pulse, it should not charge all the coil without any delay. Now i don't know. Because of the time constant, it has time to charge the capacitance only a tiny amount during the 16 ns pulse. Which may happen instantly, i don't know. But the calculations also show that the output power in your case must be very small.

[ayeaye]

What am i doing? The only thing i provide is a method of doing experiment. No new circuits or anything.

But what was i thinking. The following is the right calculation for the input part.

vl = vs - vr
pl = vl * vr / R / 1000
e += pl

Notice there, it's vl * vr / R, not vl * vl / R as i wrote before, never do that mistake. There, vr / R is really current going through the coil.

Calculation for the output part is still the same.

pr = vr * vr / R / 1000
e += pr

The following are the correct Python scripts in Trinket, use only these, not the previous ones.

Calculation of the input part and its output.

https://trinket.io/python/8b7ea90215

Input power was 0.7622 uW

Calculation of the output part and its output.

https://trinket.io/python/e181754f5f

Output power was 0.0111 uW

As you can see, the input power is almost a hundred times more than the output power. And this is likely because the pulse length is hundreds of times less than the time constant, and during that time only a tiny amount of the coil's capacitance can be charged.

Empty Trinket script, to play with. There int(s) would be a number in the input, when there is an integer on the line, or it's float(s). Output first number of the two number csv  print(int(s[: s.find(",")]))  and the second number  print(int(s[s.find(",") + 1 : ])).

https://trinket.io/python/ab5dff2b29

The Trinket online Python can also do some plotting, with matplotlib.pyplot, but only a part of it is available. The input has to be stored in a list for that. Yes sure one can plot the lists, but the image would be rather small, and the only way to save it, seems to be screenshot. I prefer to use gnuplot for plotting, but the figure below was plotted with Trinket and Python, using the following script.

https://trinket.io/python/1c378d0174