Tesla's "COIL FOR ELECTRO-MAGNETS".

[MileHigh]

Thats not true. If there is capacitance in the coil, it should be ignored, right? If we were to put a cap across a normal coil as you say, if we pulsed it like in a pulse motor, the very first thing the circuit sees is the capacitance and the circuit charges it before much happens in the coil. But in the bifi, the charging of the capacitance happens through the windings of the coil, and since the capacitance neutralizes the self inductance till the capacitance of the coil is fully charged. Talking a DC pulse of course.

Ignoring the capacitance of the coil or not ignoring the capacitance of the coil depends on what you are doing.  If you are using the coil as a drive coil for a pulse motor or as a pick-up coil for a spinning rotor then yes, you can ignore the capacitance.  Remember I crunched Farmhand's measurements on one of his coils and noted that the capacitive energy in the coil was 1/17,000th of the inductive energy in the coil under typical conditions?

If you are talking about a small coil that's on a PCB that's part of a very high frequency analog circuit design, then you probably have to consider the capacitance of the coil.  Nobody on the forums is doing very high frequency analog circuit design.

the capacitance happens through the windings of the coil, and since the capacitance neutralizes the self inductance till the capacitance of the coil is fully charged.

What do you and Farmhand and possibly others really mean when you say "neutralizes" in this context?

Why exactly should 'we' 'assume' this? What if we didnt?

It goes back to the theme of my posting.  You want to try to direct your energies and your time to where it counts.  You mechanic says to you that you should check/change your oil every 3000 miles.  Most people might only change it every 6000 miles and not check it at all and just change their oil three or four times a year.  So do you stop your car every 100 miles and get out, check the old level and smell it and contemplate changing it?  Is that good use of your time?

In a way you can say that there are kind of "electronic fetishes" that run rampant in the free energy forums and they waste a lot of people's time.  Worrying about the minuscule transient capacitance in a pulse motor drive coil would be one of them.  Some people have battery fetishes where they believe their circuit has to be connected to a battery to work properly and a regular bench power supply will "kill the effect."  Several years ago people played with car ignition coils and they noticed that their CFL lights light up brighter when they made a connection to earth ground.  So there was a crazy belief that "power comes up from the ground."  That one is still running rampant.

MileHigh

[Magluvin]

Magluvin:

Good luck in your investigations and I will make a few comments.

When you say "charge" I am assuming that you mean current flowing through the coil to energize it.  If we assume that a series bifilar coil gets the inter-coil capacitance charged right away (which would have to be verified), and we are really simplifying things here, it's still impossible to escape the fact that it takes electrical work to energize the coil and build up the magnetic field.  There seems to be a train of thought that somehow a series bifilar coil allows the coil to energize very quickly, seemingly implying that this can be done at very little energy cost.  It's simply impossible, to build up a magnetic field takes electrical work.  That work ends up being stored in the magnetic field.  The stored energy is 1/2 L i-squared.  Note for a flywheel it's 1/2 MoI omega-squared - the same formula.

There is just no "jailbreak" for energizing a coil, be it a regular coil or a series bifilar coil, which as we know is just a different winding pattern for a regular coil.  Beyond that, I am not aware of any serious analysis of this on YouTube or elsewhere.  I don't want to be a party pooper, but to the best of my knowledge this issue simply never comes up in the real world.

The true actual dynamics of how a series biflar coil actually will actually react is not trivial at all and is probably beyond the capabilities of most forum experimenters.  It's possible that your testing will show something, and it's just as easily possible that the effects will be so small that it will be hard to discern what is causing them.

For example, look at this Spice model and analysis of a transformer:
http://fmtt.com/Transformer%20SPICE%20Model%202-14-08.pdf

This image is called, "Fig. 1. Equivalent circuit of single-phase power transformer windings."
http://ars.els-cdn.com/content/image/1-s2.0-S037877961000060X-gr1.jpg

So if you are going to get "hardcore" the actual modelling of how series bifilar coil works and reacts to an outside stimulus could get incredibly complicated.

I suppose the question is is it worth the trouble?  Perhaps just an A-B comparison between two coils with the same number of turns, one regular, one series bifilar would be a good test.   Supposing you notice a tiny current inrush on the series bifilar when you energize it and you don't see that with regular coil.  Like I already said, there is no magic bypass for the energy it will take to energize either coil.

So this possible tiny current inrush, does it mean anything?  Can you do anything practical with it?   That's the real question.

The theme behind my posting is to try to recognize what's relevant and what's not relevant when you experiment.  That is an important basic fundamental skill worth learning.  Do you spend hours and hours doing some kind of special winding for a coil or do you spend 20 minutes and just wind an ordinary coil, or do you buy a spool of wire at the electronics store and have an "instant coil?"

MileHigh

"it's still impossible to escape the fact that it takes electrical work to energize the coil and build up the magnetic field."

I realize that. Never said that less energy would be used with a bifi. Just saying it seems to get to peak much faster than a normal coil. Looking into it  still.


"There seems to be a train of thought that somehow a series bifilar coil allows the coil to energize very quickly, seemingly implying that this can be done at very little energy cost."

I dont see how energizing the coil more quickly 'implies' that there is less energy cost. But that quick to energize is not the norm for a big coil.


"There is just no "jailbreak" for energizing a coil, be it a regular coil or a series bifilar coil, which as we know is just a different winding pattern for a regular coil.  Beyond that, I am not aware of any serious analysis of this on YouTube or elsewhere.  I don't want to be a party pooper, but to the best of my knowledge this issue simply never comes up in the real world."

Well we dont know this for sure yet. And yes there isnt much serious definitions of functionality of bifi out there that match what Tesla says about it. 
"but to the best of my knowledge this issue simply never comes up in the real world"
Well there may be more than one reason for that, not just that it is useless or a waste of time. Using them in a simple pulse motor may not show all its colors. This is why Im choosing to use the Arduino to accurately time the pulses to see if the coil really produces a stronger field quicker than a normal coil.


"So if you are going to get "hardcore" the actual modelling of how series bifilar coil works and reacts to an outside stimulus could get incredibly complicated."

No more than a normal coil, right? 


"I suppose the question is is it worth the trouble?  Perhaps just an A-B comparison between two coils with the same number of turns, one regular, one series bifilar would be a good test."

Yes, and yes. Ive made another plexi bobbin for a normal coil also. Like I said earlier, to get the most difference we have to have more turns. The normal coil looses its capacity with more turns, but the bifi increases it. 

A single turn coil will only have any close proximity capacitance where the ends of the coil meet. A tiny area. A 2 turn regular coil will have the 50% difference between the 2 turns measured next to each other like a bifi, but this difference decreases with every additional turn. The bifi does not.



"Do you spend hours and hours doing some kind of special winding for a coil or do you spend 20 minutes and just wind an ordinary coil, or do you buy a spool of wire at the electronics store and have an "instant coil?" "

I mostly wind my own coils. Some are old passive crossover coils. Bifi using just a role of speaker wire, the insulation would reduce the capacitance(the actual capacitance) between windings. Been looking at different litz that use larger rectangular insulated conductors woven very neatly with very little air space between each other. Then at the ends separate them into 2 bundles to create 2 separate woven windings in 1.

Mags

[Magluvin]

I Have a reply for Farmhand to one of his posts today in the confirming delayed lenz thread, where ill show the inside of my bike motor and another little treasure that I found from spare parts at work from a VW Touareg that I will be working with soon.

Forgot to mention that I realized it was this thread that Farmhand posted. Got lost with my original second post. Pics above.

Mags

[TinselKoala]

Kenneth Corum and James Corum.

There is a lot of misunderstanding and even disinformation about Tesla, Tesla coils, and the Tesla bifilar winding patent, and series bf vs. parallel bf vs. ordinary winding, etc. The Corums get it right, but their work is highly technical and hard to find in "condensed" form.

Tesla wanted low resonant frequencies with as little wire as possible and without the expense and difficulty of large and expensive and dangerous HV capacitors. A precisely constructed and tuned, flat pancake "series bifilar" coil's greatly increased self-capacitance allowed him to achieve that goal. His purpose was to attain very fast (for those days) rise and fall times in the primary coils of his power systems. The faster the transitions in the primary, the greater the voltage induced in the secondary. This is why, for example, modern square-wave SSTC drivers are able to pump up such high secondary voltages without HV in the primary or spark gaps: the fast rise and fall times of the pulses is accomplished by the modern semiconductors and the driver circuitry.
The "ideal" Tesla coil/power transmission system might consist of a low-frequency secondary, driven by a Tesla bifilar primary, using no tank capacitor but only the coil's self-capacitance, to attain a low resonant frequency of its own, matched to the secondary. Such a coil would have to be physically large and very precisely constructed, and it's doubtful that even modern semis, like large IGBTs, would be able to handle the stress of driving it at high power levels.

There are winding schemes that have "special" effects on coils. I think these do things like change the ratio of DC resistance to the inductance attained in the coil. Take a look at some old radio RF coils or chokes. You will see all kinds of mysterious winding patterns. Even my simple loopsticks have a dual coil, separated by a specific gap, and each coil is wound in a herringbone crossover pattern, very neatly, with cotton-covered, enamelled Litz wire. You can be sure that the makers would not have bothered to do this if a simple single, random-wound coil of the same amount of wire would 'do the trick'.

[Farmhand]

Nice motor and alternator Mags, I'll have to have a close look at the pictures, thanks ! Not using one side of the magnetic field of a very low loss inductor will not waste much energy Mags, at most it will waste some space I think. If the inductor has zero Ohms DC resistance it would have almost no losses, the loss is in the heat from the resistance or how you use the coil. 

MileHigh, Some of us do experiment with high frequency stuff, and when we tune a circuit to resonance every pF of capacitance matters quite a bit in some places. ie, a few pF is nothing to the 240v input or even the 2000v out from each MOT at 50 Hz but a few pF in the elevated toroid or sphere terminal is what we tune with or to. It cannot be ignored period. If we did ignore it we would never get our big coils tuned properly and throwing large sparks continuously or any light from fluro's in the hand with small coils ect. If a resonant coil is working at around 1 mHz or so and it only has 30 or 40 pF in it's entire resonating circuit then 2 pf makes a big difference, if there was no need for resonance it wouldn't make any difference. Maybe a lot of Tesla's stuff doesn't make much sense unless the resonance aspect is considered as part of the intended working principal of the circuit. Without worrying about resonance a few hundred pF means nothing yes, no doubt about it. But if we want resonance and the capacitance is small (and the frequency high) every pF matters.

Cheers

P.S. MileHigh, By "neutralizing the self inductance" we mean "neutralizing" the effect of the delay in the flow of current because of the self inductance, which is what Tesla wrote in the patent. At resonance we can have a lot more current flow more easily through a coil, my pulse motor is a prime example when the circuit is not at or near resonance frequency the inductance restricts the flow of current as in the usual way, but when at or near resonance current flows without much regard to the inductance because the current limiting effects are neutralized. We still get the magnetic power of the high inductance coil but the current can flow more than with no resonance, that's the point. Why wait so long for the current to flow through a coil if we don't need to or try to force it.

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