Some tests on mono and bifilar coils

[MileHigh]

Conrad:

In reference to your coil resonance measurements and self-capacitance calculation:

Since you are seeing such a radically different self-capacitance between the two coils you wound, I would think it merits some further consideration and testing.  I believe that others have shown only a marginal difference between the self-capacitances between two similar coils, including you yourself if I recall correctly for a different build.

My suggestion would be to measure the self-capacitance in one or two other ways to see if you get consistent results in accord with your first set of measurements. I am not saying your measurements are wrong.  Rather, I am saying that they merit being double-checked via one or more alternative methods.

MileHigh

[gyulasun]

Well the theorem seems to hold, it can tell us what resistance will show the most power for a given coil at a certain frequency. if the speed changes during tests and so forth (unlike a wall transformer) then some tuning would be needed, but the Theorem can guide us to max power output maybe. Interesting.

Cheers

Hi Farmhand,

Yes, the Thevenin theorem is useful, it reveals (among other things) that the inductive reactance of the generator coil also influences the output power when trying to use a "matched" load: in fact for AC generators a 'complex conjugate' load would represent a perfect power match. IT means a tuned case where the inductive reactance of the gen coil is compensated by an equal value capacitive reactance on the load side and there remains the DC resistance of the generator coil to be also matched for the resistive part of the load (a real power factor compensation if you like).

This condition is nicely fulfilled in this setup, because the coils reactance is surely compensated for by the 10 uF tuning capacitor and there is resonance, still Conrad found that a higher power output can be had by using a cca 420 Ohm load resistor instead of using a load equal to the coil DC resistance.  The explanation is that for a parallel LC resonant tank circuit, when the load comes also in parallel with the tank, it is the unloaded Z impedance of the tank which is to be considered as the impedance to be matched to the load. This unloaded Z impedance is governed by the Q quality factor of the tank, mainly by the coil, the Q is Q=XL/r and then the Z impedance is Q*XL. So the unloaded Q comes out as roughly 2.7 (monofilar coil with ferrite, at 95 Hz, r=77 Ohm) and the Z impedance comes as roughly 575 Ohm (this a little higher than the 425 Ohm Thevenin value but maybe still within ballpark). So perhaps the correct power-matched load would be around 570 Ohm for the monofilar coil case. 

IF you arrange the generator coil so that the load would be connected in series with the 10 uF capacitor (i.e. you would have a series LC tank into which you would insert the load) then the power matched load would really be that of the coil's DC resistance i.e. the 77 Ohm (provided that the core and capacitor losses would be negligible with respect to the loss on the 77 Ohm). This is because in a series resonant LC circuit there is no transformed Z impedance towards a load when inserted also in series into the series LC circuit, while in case of a parallel LC tank with a parallel connected load, the mainly coil's DC resistance gets transformed up by the Q of the LC tank to establish the tank impeadance which is a real resistive value at resonance.

Gyula

[Farmhand]

That makes complete sense even though I didn't look into the calculations, yet !  I hope you guys know we do learn a lot from a well worded response like that.  Thank you very much Gyula.

So it would be interesting if Conrad did try the higher resistance you calculated and also tried to get a similar power transfer via the series circuit. I applaud Conrad for his perseverance and willingness to embrace learning. It really helps others like me as well. I need to be able to calculate reactance to be expected from a given coil at a certain frequency. Would be very helpful to be able to wind to a target "output impedance".

Cheers

[synchro1]

The "Old Scientist" measures one half the resistance 5.86 Ohms in his series bifilar solenoid compared to the single wire solenoid of same wire length and gauge at 11 Ohms. I don't understand why you indicate the same resistance in both types of coil wraps in contradiction to the "Old Scientisit's" measurements, or am I missing something? The disappearance of half the Ohmic resistance in Tesla's SBC amounts to a deep mystery to me. Haven't you tested for this difference yet?



http://www.youtube.com/watch?v=uNAZ6heorEc&list=UUNbdkwT-LstmshlLDOqs7JA

@Conradelektro,

Voltage is inversely proportional to Ohmic resistance, so it would follow that the SBPC with half the Ohms would only require half the voltage to produce the same magnetic field strength. Why not retry those magnetic compass deflection experiments once more with half the voltage in the SBC pancake, and see if the field strength remains equal?  

[conradelektro]

Gyula, thank you for the Q factor calculations (I documented this method in the attached PDF file).

I tested a few more load resistors (300 Ohm, 570 Ohm, 1000 Ohm) which were connected after the pick up coil was in resonance (90 Hz) with the parallel 10 µF cap. Depending on the load resistor (short circuit up to 1000 Ohm) the speed up and the reduced power draw were more or less pronounced.

It seems that a load resistor of around 420 Ohm gives the highest output of 0.44 Watt in the load resistor (but also a considerable power dissipation in the parallel LC circuit of 0.59 Watt). A load resistor of 85 Ohm or a short circuit gives the highest speed up, the lowest power draw of the motor and an equal power dissipation in the LC circuit and in the 85 Ohm load of about 0.27 Watt.

See the attached PDF-file for all measurements.

I will now measure the self resonance and the self capacitance of the two coils with different methods (the method I already did was with an exciter coil of three turns), see this post http://www.overunity.com/14235/some-tests-on-mono-and-bifilar-coils/msg386148/#msg386148

Greetings, Conrad

For all who are not closely following  this thread, look at this post to understand the "speed up under load" experiment http://www.overunity.com/14235/some-tests-on-mono-and-bifilar-coils/msg386184/#msg386184