Tesla's "COIL FOR ELECTRO-MAGNETS".

[Magluvin]

Was thinking about how to keep the 2 wires together while winding. I remembered today I saw a guy that used an empty pen to guide and feed the wires around his star coil. I think its the guy with the Dean Martin hat and has part in the pulse motor buildoffs. Anyway, I buy this Chair Repair superglue from Ace and it comes with a couple siring looking applicators that I fitted to a piece of 1/8in pvc tube. Pic shows 1 wire and it looks like 4, 5 or 6 or maybe 10 could fit. I cannot find anything smaller at the moment. Possibly if I keep the tip bent a bit, the wires will stay together better.

Another way would be to twist the pairs as I wind. Lol, even thought of how to run the wire off the 2 spools and they are mounted to a spinning wheel. I make a jig that once the wires come off the spools, they are directed back and over the spinning wheel with spools, and the winding of the wire to the new bobbin is what spins the wire wheel to twist the wires.

But twisting them would take up space on the coil.

So we will see if the capacitance is different with this coil. if not, then I have to blame it on not enough surface area of smaller wire and capacitance suffers. Would seem strange, all that density of fine copper and little air space. If thats the case then flat or square wire would be the next best bet at getting the most capacitance.

Mags

[MileHigh]

Farmhand:

I looked at your clips and you may be observing some similar effects but it's hard to tell from the viewpoint of the watcher of the clip.  Your comments and observations about being on resonance vs. off resonance are correct like you stated, but real measurements with a scope and everything else make a difference.

Conrad has a great test setup.  For example, a typical experimenter connects a load resistor and the pulse motor speeds up past the resonance point and they call that the "delayed Lenz effect."  What about what happens when you connect a load resistor and you want to still measure what happens at resonance?  That's more interesting information.  With Conrad's setup he just has to lower the voltage to the DC motor and then run at the resonance frequency and make some more measurements.  This allows you to do a nice A-B comparison:  Behaviour with and without a load resistor at the resonance frequency.  Note you can still measure the DC motor power consumption.

Likewise, you have to consider the wire resistance of the coil relative to the resistance of the load resistor.  You can always measure the power dissipation in the load, or in the coil-load combination.  It's all relevant data that can't be ignored if you want to track where the power is going.

And impedance matching is the dominant factor in all of this.  With a pickup coil with a load resistance that varies between zero ohms and infinity ohms and no capacitor, we know that there is no power dissipation in the load resistor at either extreme because it is a complete impedance mismatch.  Likewise, we know that at the matched impedance you get maximum power dissipation in the load resistor (and in the coil.)  Something similar is happening when you throw the capacitor in the mix.  Resonance comes into play and tends to make the coil suck more power to burn off in one or both resistances, but clearly impedance matching is coming into play just the same.  Note even with a cap, if the load resistor is zero or infinity, you still get zero power transfer into the load.

Is there really and truly a "delayed Lenz effect?"  The answer is almost there, you just have to look for it.  It's such an easy experiment also.  You just put a tiny sensor coil on the other side of the spinning rotor magnet.  With some care and some experimentation you can find a way to use the sensor coil as a scope trigger and as a top-dead-center indicator relative to the real pickup coil.  Then you simply look at the current waveform for "no delayed Lenz" and "delayed Lenz."  You will be able to precisely determine if the pickup coil is in repulsion or attraction as the rotor magnet spins by, by carefully analysing the current waveform in the coil relative to the angular position of the rotor magnet.  You do the A-B comparison with the no-capacitor case at the same frequency.

Let's assume that you do the A-B comparison test and you find that there is a phase shift in the current waveform and the onset of Lenz repulsion or attraction is indeed delayed when you add a load resistor and the motor speeds up.  That's interesting but the real action is all about the overall impedance of the (coil + load resistor + capacitor).  It's the impedance match or lack of impedance match that determines the amount of power burned off in the real load resistor.  That determines the Lenz drag and that determines the rotor speed.  The phase angle of the current waveform in the pickup coil is related to the impedance but you still must look at everything if you really want to know what's going on.

The source impedance is somewhat abstract.  It's related to the rate of changing magnetic flux from the spinning rotor magnet interacting with the pick-up coil.  The magnet only has so much flux and likewise the motor can only output a certain amount of power.  It's how the pickup coil + load resistor + optional cap match that source impedance and draw power from it.

Conrad will do his thing and pursue his own line of investigation.  You can certainly appreciate that he has a great test bed and he is pretty much in control of most or all of the variables.  For me, it's great to see how he is really using his scope to monitor the current and the voltage in the pickup coil setup.  Modern scopes spit out live RMS voltage readings, it's almost too good to be true.

MileHigh

[tinman]

This reminds me of my old LAG-lenz asisted generator project's-way back then lol.
Please excuse my green understandings of days past.

https://www.youtube.com/watch?v=oKb3F61cg_s

Test data video.
https://www.youtube.com/watch?v=Tv8SGxWNELo

[conradelektro]

Hi Conrad,

When you have some time, would you make a scope shot of the voltage and current when the air core coil have the max output with the 100 Ohm load at about 200 Hz?  If the shot is very similar to what you have so far showed just in the previous post, then of course no need to make it, just mention that.  (I am interested in the phase relationship under this condition.)

EDIT: A strange thing I observe: when you have a voltage max at about 52 Hz by the scope measurement (loaded case, with bolt, series bifi, motor input 4.4V/1.68A from your video ),  the 10 uF capacitor needs 936.7 mH coil inductance to get resonance at 52 Hz.  How is it possible I wonder, the bolt makes your series bifi coil to be 520 mH.

Thanks,  Gyula

@Gyula:

Steel core: I think that the mild steel bolt causes strange effects, e.g. that the inductance is very high at low frequencies. The inductance at 100 Hz is about 520 mH and drops fast with rising frequency, and it could well be 930 mH at 50 Hz. The steel bolt is useless and introduces too many unknown factors. For Ferrit core tests I have to wind two new identical coils (one monofilar and the other bifilar) over a 10 mm Ferrite core, what I want to do anyway soon. I can not fit my 8 mm Ferrite core into the big coil I am using now. And a 6 mm Ferrite core would rattle (that is why I did not buy it).

Air core: The big problem with the scope shots is the placement of the oscilloscope probes, specially the GND of the probes (which has to have the same potential for both probes). See the attached circuit diagram, I have changed the placement of the probes and the scope shots might look more familiar to you concerning the phase shift of current.

In the original cope shots the phase of current and Voltage was 180° shifted due to the placement of the probes and therefore it was unfamiliar for you.
Original scope shots (air core) are at: http://www.overunity.com/13460/teslas-coil-for-electro-magnets/msg384192/#msg384192

Attached please find the new scope shots with the new placement of the scope probes.

- The two top scope shots show the "speed up effect". (Voltage over the motor was not changed, only the 100 Ohm load was switched on).

- The two bottom scope shots are at higher speeds (222 Hz and 281 Hz) with the 100 Ohm load still on. The Voltage over the motor had to be increase to get to these higher speeds. You see that at 222 Hz the output was higher than at 281 Hz. Starting with 200 Hz there is no increase of the output (although the motor needs ever more Voltage and Amperage).

I will test with a variable resistor as a load next (air core).

Greetings, Conrad

[conradelektro]

This reminds me of my old LAG-lenz asisted generator project's-way back then lol.
Please excuse my green understandings of days past.

https://www.youtube.com/watch?v=oKb3F61cg_s

Test data video.
https://www.youtube.com/watch?v=Tv8SGxWNELo

@tinman: I looked at your "LAG", very impressive. Could you please post a link to more information. At what stage is the project?

I did not try to build a new motor, I use an ordinary 12 V DC motor to spin a diametrically magnetised ring magnet. And I put a 10 µF cap in parallel with a generator coil placed in front of the spinning magnet.

The big 10 µF cap (in parallel with the generator coil) serves to simulate a generator coil with a massive self capacitance in order to bring the (faked) self resonance down to a low frequency (in this case 52 Hz). According to my opinion this allows to simulate the so called "reduced Lenz drag" or the "speed up under load" (what your LAG is doing).

Have a look at my video http://www.youtube.com/watch?v=vAXQBpuLu68 . I would be interested in your opinion, since you built a LAG.

Greetings, Conrad