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Author Topic: Bifilar pancake coil overunity experiment  (Read 93414 times)

Void

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Re: Bifilar pancake coil overunity experiment
« Reply #360 on: December 26, 2018, 05:26:54 PM »
Hi Brad.

What was the frequency of operation there? Was the scope set to 50nS per division? 13 MHz approx. ? ? ?
... or am I reading that wrong? Are you using non-inductive resistors for the CSR and load resistor?
It is looking like your load resistor R2 may actually be inductive, and if that is the case that could cause
the current reading across it to read considerably higher than the true resistive load current.

It is possible that Vin and Iin could be close to being in phase if the pancake coils are being driven
at a frequency that is close to a resonance point for them.

Also, see the attached picture of your latest test setup with some additions from me.
I have indicated three different currents: I1, I2, and I due to capacitive coupling back to the function
generator ground. All three of these currents are not equal in both magnitude and phase angle! These
are three different currents. The current returning to the function generator via capacitive coupling bypasses
the CSR R1. Your measurement of the input current therefore will not be accurate IMO.

It is for this reason that I said that I think using a current probe at the 'positive' output wire
of the function generator is probably the best representation of the input current for this type of setup,
assuming the current probe is reading reasonably accurately for both magnitude and phase angle.  However,
due to the complexities in making accurate measurements in this type of setup, I personally would still
not have a high degree of confidence in the accuracy of those measurements even when using the current probe.
That is just me however. :)


ayeaye

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Re: Bifilar pancake coil overunity experiment
« Reply #361 on: December 26, 2018, 05:38:11 PM »
As much as i know, current in a single closed loop is everywhere the same, and its phase is the same.

If F6FLT or someone else points out some great difficulties in measurement, yes, oscilloscope is all about accuracy. My suggestion is then, measure some simple circuit, like a one containing only a capacitor, with similar frequency and voltages. Then simulate the same in LTspice, and see how great the error is.


Void

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Re: Bifilar pancake coil overunity experiment
« Reply #362 on: December 26, 2018, 06:02:37 PM »
As much as i know, current in a single closed loop is everywhere the same, and its phase is the same.

Hello ayeaye. If you look at the diagram I attached above, it should be clear that such a circuit, where an open ended
coil is being driven from the generator, is not a 'single closed loop'. It is therefore not so straight forward
to make accurate measurements on such a setup.


tinman

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Re: Bifilar pancake coil overunity experiment
« Reply #363 on: December 27, 2018, 04:09:35 AM »
Hi Brad.

What was the frequency of operation there? Was the scope set to 50nS per division? 13 MHz approx. ? ? ?
... or am I reading that wrong? Are you using non-inductive resistors for the CSR and load resistor?
It is looking like your load resistor R2 may actually be inductive, and if that is the case that could cause
the current reading across it to read considerably higher than the true resistive load current.

It is possible that Vin and Iin could be close to being in phase if the pancake coils are being driven
at a frequency that is close to a resonance point for them.

Also, see the attached picture of your latest test setup with some additions from me.
I have indicated three different currents: I1, I2, and I due to capacitive coupling back to the function
generator ground. All three of these currents are not equal in both magnitude and phase angle! These
are three different currents. The current returning to the function generator via capacitive coupling bypasses
the CSR R1. Your measurement of the input current therefore will not be accurate IMO.

It is for this reason that I said that I think using a current probe at the 'positive' output wire
of the function generator is probably the best representation of the input current for this type of setup,
assuming the current probe is reading reasonably accurately for both magnitude and phase angle.  However,
due to the complexities in making accurate measurements in this type of setup, I personally would still
not have a high degree of confidence in the accuracy of those measurements even when using the current probe.
That is just me however. :)

Hi Void

Yes,turns out these !so called! non inductive resisters become quite inductive after 2MHz-ok below that.

Swapping it out for a 1/2 watt carbon resistor made all the magical OU disappear  :D


Brad

Void

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Re: Bifilar pancake coil overunity experiment
« Reply #364 on: December 27, 2018, 04:42:28 AM »
Hi Void
Yes,turns out these !so called! non inductive resisters become quite inductive after 2MHz-ok below that.
Swapping it out for a 1/2 watt carbon resistor made all the magical OU disappear  :D
Brad

Hi Brad. Ha ha. Ok, yes, it was kind of looking like that might well be the culprit when I
was looking over your test setup and measurement results. Have a happy new year guys!


ayeaye

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Re: Bifilar pancake coil overunity experiment
« Reply #365 on: December 27, 2018, 09:58:47 AM »
Swapping it out for a 1/2 watt carbon resistor made all the magical OU disappear  :D

Ok, thank you for finding it out. Means that we should go back to the beginning? As these circuits with a weird way of using bifilar coil, after all appeared to be no way to go. You got overunity results at very high frequencies, yes 13 MHz, inductive resistors that supposed to be non-inductive, may explain this.

Void, you should somewhat more understand the basics. The figures below are made with geda, which is a spice simulator like LTspice. See that the current has always the same phase, no matter where in the circuit. In spite that there is both a capacitor and an inductor in the circuit. It has the same value everywhere too, but i made one resistor two times greater than the other, so that both traces can be seen. See that the current somewhat leads the voltage, because in spite of the inductor, the circuit is mostly capacitive. It is true when the circuit is all connected in series (when all is one loop). It is not true about the current in parts connected in parallel in some components of the circuit.

The direction of voltages below is correct in accordance with the kirchoff's law. One may ask why is the voltage on the voltage source inverted. It is, as the movement of the assumed positive particles is from + to - in the voltage source, when the power is consumed. But the voltage on the rest of the circuit is not inverted, and this is what one should use, like when calculating power.

Indeed try to measure some simple circuit, like that on the figure below, with only a capacitor and a simple coil, with the same components that you use and the same ways of measurement. Then simulate it in LTspice and see how much it differs. That way you will see at once when some resistors are inductive or anything else is not how it supposed to be.


tinman

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Re: Bifilar pancake coil overunity experiment
« Reply #366 on: December 27, 2018, 11:46:37 AM »
Hi Brad.

What was the frequency of operation there? Was the scope set to 50nS per division? 13 MHz approx. ? ? ?
... or am I reading that wrong? Are you using non-inductive resistors for the CSR and load resistor?
It is looking like your load resistor R2 may actually be inductive, and if that is the case that could cause
the current reading across it to read considerably higher than the true resistive load current.

It is possible that Vin and Iin could be close to being in phase if the pancake coils are being driven
at a frequency that is close to a resonance point for them.

Also, see the attached picture of your latest test setup with some additions from me.
I have indicated three different currents: I1, I2, and I due to capacitive coupling back to the function
generator ground. All three of these currents are not equal in both magnitude and phase angle! These
are three different currents. The current returning to the function generator via capacitive coupling bypasses
the CSR R1. Your measurement of the input current therefore will not be accurate IMO.

It is for this reason that I said that I think using a current probe at the 'positive' output wire
of the function generator is probably the best representation of the input current for this type of setup,
assuming the current probe is reading reasonably accurately for both magnitude and phase angle.  However,
due to the complexities in making accurate measurements in this type of setup, I personally would still
not have a high degree of confidence in the accuracy of those measurements even when using the current probe.
That is just me however. :)

Yes,like i posted in reply 278,when looking at the other circuit.

I do mostly agree with what you say,although there are some points that need more study --to me anyway.

Brad

ayeaye

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Re: Bifilar pancake coil overunity experiment
« Reply #367 on: December 27, 2018, 12:09:55 PM »
Tinman, why is that capacitor drawn there in your circuit? The equivalent circuit should be something like that on the figure below, with no capacitance where you drew it. Or is it a yet another modification of the circuit?

That capacitance sure adds capacitance to the circuit loop. The only place in that circuit where the current may be different in value or in phase, is in the resistor R1, because it is parallel to the secondary winding of the bifilar coil. In all the rest of the circuit the current is everywhere the same.


tinman

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Re: Bifilar pancake coil overunity experiment
« Reply #368 on: December 27, 2018, 02:10:40 PM »
Tinman, why is that capacitor drawn there in your circuit? The equivalent circuit should be something like that on the figure below, with no capacitance where you drew it. Or is it a yet another modification of the circuit?

That capacitance sure adds capacitance to the circuit loop. The only place in that circuit where the current may be different in value or in phase, is in the resistor R1, because it is parallel to the secondary winding of the bifilar coil. In all the rest of the circuit the current is everywhere the same.

It is to indicate the small amount of stray capacitance that creates a small current loop,such as void was talking about in post 360.


Brad

tinman

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Re: Bifilar pancake coil overunity experiment
« Reply #369 on: December 27, 2018, 02:13:48 PM »

 In all the rest of the circuit the current is everywhere the same.

No
When dealing with these BIFI pancake coils,the current is different throughout the bifi coil windings,and the value at each point depends on frequency.
It will only be the same at the start and end of the coils.

Watch this video,and see what you think.

https://www.youtube.com/watch?v=2JK7PYBdMUI


Brad

ayeaye

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Re: Bifilar pancake coil overunity experiment
« Reply #370 on: December 27, 2018, 02:47:10 PM »
No, i didn't say that current is the same everywhere inside a bifilar coil. Bifilar coil is not a single branch, it is two coupled windings connected with capacitance. In addition to capacitance, a current moving to the capacitance induces current in the other winding.

Tinman, your video can be easily explained. At higher frequencies the resistance of the capacitance decreases a lot, thus naturally most goes through the capacitance and not the other way. Some things were rather interesting, like the lightness of the led-s changed quite arbitrarily, i cannot quite explain that. This is not enough though to replace my interest in overunity.


Void

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Re: Bifilar pancake coil overunity experiment
« Reply #371 on: December 27, 2018, 07:58:56 PM »
It is to indicate the small amount of stray capacitance that creates a small current loop,such as void was talking about in post 360.

Hi Brad. At frequencies in the high kHz and into the MHz range, that capacitive coupling current return
to the function generator ground can be quite significant. 100 pF at 1 MHz has an impedance of only around 1.6 K Ohms,
for example. If high voltages are being generated on the coil assembly, for example if one or both coils
is operating at resonance, a significant current (relatively speaking) can flow there. At resonance, single ended
coils can create a significant ground return current (significant relative to the input power level).
« Last Edit: December 27, 2018, 10:29:21 PM by Void »

ayeaye

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Re: Bifilar pancake coil overunity experiment
« Reply #372 on: December 27, 2018, 09:10:54 PM »
that capacitive coupling current return to the function generator ground can be quite significant.

This was essentially the first thing that i said after i saw the TinselKoala's video. There are two current paths, but he measured only one. Then Partzman said that this second return path is insignificant and i finally agreed, as this capacitance is sure much smaller than the capacitance in the bifilar coil. But to really find out, it can always be measured.


F6FLT

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Re: Bifilar pancake coil overunity experiment
« Reply #373 on: December 28, 2018, 04:03:32 PM »
Hi Brad. At frequencies in the high kHz and into the MHz range, that capacitive coupling current return
to the function generator ground can be quite significant. 100 pF at 1 MHz has an impedance of only around 1.6 K Ohms,
for example. If high voltages are being generated on the coil assembly, for example if one or both coils
is operating at resonance, a significant current (relatively speaking) can flow there. At resonance, single ended
coils can create a significant ground return current (significant relative to the input power level).

It reminded me of a recurring problem for feeding the radio antennas, due to current on the shielding braid of the coaxial cables.
The solution, which could be applied to the cables of the FG and of the scope probes, is to wrap a few turns of the cables in ferrite toroid cores. The inductance created in this way has a high impedance that prevents or reduces ground currents.
But here there is a risk: aggravating the problem by creating resonance effects, especially if the impedance is not high enough! Only a test can tell us if it works.


tinman

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Re: Bifilar pancake coil overunity experiment
« Reply #374 on: December 28, 2018, 04:25:26 PM »
Hi Brad. At frequencies in the high kHz and into the MHz range, that capacitive coupling current return
to the function generator ground can be quite significant. 100 pF at 1 MHz has an impedance of only around 1.6 K Ohms,
for example. If high voltages are being generated on the coil assembly, for example if one or both coils
is operating at resonance, a significant current (relatively speaking) can flow there. At resonance, single ended
coils can create a significant ground return current (significant relative to the input power level).

In my case,i dont think it would be of any value that would skew the measurements to much,as the max voltage across the coil was only about 13 volts peak.

Like all coils,i can make this one mostly inductive,mostly capacitive,and purely resistive,simply by changing the frequency.
See screen shots below.

Brad