Bifilar pancake coil overunity experiment

[tinman]

I was using a battery operated (so ground isolated) FG all the time as mentioned before.
I used also an isolation transformer to be compatible with TK his setup.


Anyway, latest setup from F6FLT:

Still using the 2th bifilar coil.

Math function cannot be used in this setup (1 math function at a time only for my scope).

Screenshot 1 shows the values:

CH1 = 1.786V
CH2 = 1.750V
CH3 = 868.8mV
CH4 = 44.4mA   (i added the current probe value (right before R2 in the diagram) to show the difficulty to correctly
                           measure the voltage (current) across R2 (CH1 - CH2) in this setup)

Difference between CH1 and CH2 is 36mV, but this is very debatable, see lateron.

Calculating:

Pin = CH1 * (CH1-CH2)/R2
Pin = 1.782 * (1.782-1.75)/1
Pin = 64.29mW

Pout = CH3²/R1
Pout = 0.8688²/20
Pout = 37.74mW

COP = 37.74/64.29 = 0.58

Using the current probe value of 44.4mA, then we get:
Pin   = 79.2mW
Pout = 37.74mW
COP  = 0.47


But.......

note the phase difference between CH1 yellow and CH2 blue, its 0, meaning pure resistive.
note the phase difference between CH4 green and CH2 blue, its -52° (plus 10 = -62°) which should be 0 as both are measuring the same current!!

So something is not right in this setup.

If i remove all probes (grounds) and only measure across R2 together with the current probe i DO get both signals
to be of the same value (45mA) plus of the same phase see screenshot 2.

thoughts?


Itsu

Itsu

I would do with your current probe as i did with mine-->file it on the top shelf ,and forget about it.

Your current probe is doing exactly what mine did in the higher frequencies--lagged behind actual current. This tells me that the probe is some what capacitive at the higher frequencies.

I have never liked current probes being used at these low power ratings.
Your yellow and blue trace are correct,which means your current probe (green chanel) is reading incorrectly. Maybe it is to close to one of the coils,and picking up external magnetic fields?.


Brad

[F6FLT]

I have mentioned some reasons why measurements on these types of circuits can be very tricky,

Only the drawing is tricky. L1 is connected to L2 with a capacitor. Draw the capacitor and the mystery disappears. That what I did for my LTspice model, and it reproduces perfectly my bifilar coils.

[itsu]

Itsu

I would do with your current probe as i did with mine-->file it on the top shelf ,and forget about it.

Your current probe is doing exactly what mine did in the higher frequencies--lagged behind actual current. This tells me that the probe is some what capacitive at the higher frequencies.

I have never liked current probes being used at these low power ratings.
Your yellow and blue trace are correct,which means your current probe (green chanel) is reading incorrectly. Maybe it is to close to one of the coils,and picking up external magnetic fields?.


Brad

Brad,

i don't think so, when using ONLY the current probe and ONE voltage probe across the csr, the  both show the
SAME amplitude AND phase, no lagging behind, see 2th screenshot above.

I rather think that in the multiple probe setup (1st screenshot), the blue CH2 is somehow "forced" to join up
with the phase of CH1 yellow due to the same ground points.

I would rather "believe" the current probe here then the voltage probe.

Itsu

[Void]

I have mentioned that once the scope probes are connected to the circuit and the circuit is running,
you should try moving the scope probe leads around and watch the scope display to see if the phase
difference shown between waveforms is changing when you do this. Has anyone tried this?

My guess is the electromagnetic field around coils may sometimes couple into the
scope probe leads directly which can throw phase measurements off. I have found that how
much of an issue this is depends on the exact circuit configuration and frequency of operation.
Obviously if the phase difference shown on the scope is shifting around as you move the scope probe
leads around (while the scope probes are connected to the circuit) then you can't trust the phase measurements at all.

Experienced engineers/technicians who build and test circuits like this at higher frequencies will build the circuit on a ground
plane to make the circuit more stable against stray capacitance, and keep all lead wires as short as possible, etc., and do other
things like keeping scope probe leads at right angles to coils and that sort of thing as well. Even then the measurements can be
quite difficult to do accurately. Taking accurate measurements on setups like this is an art in itself.

The bottom line is experienced OU experimenters know the importance of trying to self-loop any circuit setup that
you think might be showing OU. There is just too much room for being mislead in one way or another otherwise.

[F6FLT]

...
Difference between CH1 and CH2 is 36mV, but this is very debatable, see lateron.
...

I had anticipated this difficulty. To remove it, a differential measurement could be the solution. On my old Tektronix I could choose to display channel A-B. I don't know if it's still possible with modern scopes as yours (or my Siglent, not yet searched for that).