Tesla's "COIL FOR ELECTRO-MAGNETS".

[Magluvin]

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'.

"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."



"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."



"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."

I remember these. Some with a tube core with an adjustable core in the vertical tube and some with 2 coils like you say but spaced apart. Found a pic shown below. Its not exactly as I remember. I had an old AM SW MW radio when I was a kid that I found in a building of an old abandoned park from the early 1900s. The wood case was lierally disintegrated. But I got that thing to work.  It had the tuning eye tube. Remember those?    I loved that radio. Learned a lot from it. Memories.

Here is a site that talks about different coils and why. English on the left. Deutsch on the right.

http://www.oldradioworld.de/gollum/hcoils.htm     


"driven by a Tesla bifilar primary, using no tank capacitor but only the coil's self-capacitance"

Hmm, just put the spark gap across the input leads?  Nice.

Thanks 

Mags

[Magluvin]

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.

No no. what I mean is that other side of the coil , for imaginary purposes, can drive another rotor without speed drop of the first rotor. Geddit?      So if you had a core that directs the N and S of the coil to just one rotor where the N of the coil is pulling on the rotor magnet and the S of the coil is pushing at the same time, you will get more motive force on the rotor.  That was all I was suggesting.


Mags

[Magluvin]

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.

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

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

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

And possibly others? lol  Tesla had the patent and he said it.  What do you think it means in your context?


"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."

Fetishes? Why dont you top it off with a used condom across the page. That would be a huge deterrent. You really dont like the idea that people work with this coil do you?

This is what I like about the idea of the coil reacting quicker for a pulse motor. There will be more of an impulse than a gradual climb in current flow when the coil is being pulsed. We are talking 'pulse' motors. A quick pulse has more impact, impulse. It pops, no waiting period, no mooshy mooshy. Like using a small sledge hammer vs a rubber mallet of the same size.
Another thing is, lets say we have a simple pulse motor. 12v batt, normal coil, rotor with magnets and a reed switch. When we close the reed, it will take some time for the field to build due to impedance. And when it finally peaks or even sustains peak for the duration of the switch closure and the reed releases and waits for the next mag pass. But once we get to higher revolutions, the pulse times will be shorter with less time for the field to build. But the fast acting bifi will be able to react more quickly with more controlled on and off times and better high rpm performance.

Now we try something different. We use a large inductor and a diode added to the circuit. What we are going to do is use the reed to charge up the new large inductor and when the reed releases, let the collapse current of the large inductor dump into the motor driver coil to run the motor. But oh, the motor driver coil will not accept the collapse current due to impedance so the reed burns instead.

But if the motor driver coil is a bifi, even a big one, it will accept that collapse current, not the 'norm', which will charge that tiny capacitance of the bifi to possibly many hundreds of volts.  and     

This is an idea I have from understanding the workings of the 'Igniter for Gas Engines' and the 'Coil for Electro-magnets', as to what is described, where we use the large inductor efficiency from the igniter to charge the bifi for a pulse at a higher potential than the batt input. We are charging the bifi capacitance with an inductor not from the battery directly, or we would lose half the energy used from the battery to charge the cap directly.    This is a much different way of doing things than we are used to.

And its way more fun than building a universal motor. Been there done that been done. Lets move on to new things. Standing still will get you nowhere.


Mags

[MileHigh]

I am just catching up!  No time to read other thread.

Farmhand:

I can never remember which is which so I had to check.   Looking up LC circuit yet again....

Wiki quotes....

The charge flows back and forth between the plates of the capacitor, through the inductor. The energy oscillates back and forth between the capacitor and the inductor until (if not replenished by power from an external circuit) internal resistance makes the oscillations die out. Its action, known mathematically as a harmonic oscillator, is similar to a pendulum swinging back and forth, or water sloshing back and forth in a tank. For this reason the circuit is also called a tank circuit. The oscillation frequency is determined by the capacitance and inductance values. In typical tuned circuits in electronic equipment the oscillations are very fast, thousands to millions of times per second.

In a series configuration, X_C and X_L cancel each other out. In real, rather than idealised components the current is opposed, mostly by the resistance of the coil windings. Thus, the current supplied to a series resonant circuit is a maximum at resonance.

The parallel LC circuit connected in series with a load will act as band-stop filter having infinite impedance at the resonant frequency of the LC circuit. The parallel LC circuit connected in parallel with a load will act as band-pass filter.

.......

I view a self-resonating coil as a parallel LC circuit.  Which would mean it blocks a signal passing through it at the resonant frequency.  I am just not sure how you are applying whatever resonance concepts to your circuit or motor.  If either form of resonance is associated with "neutralizing the self inductance" keep in mind we are talking about a pure sinusoidal excitation waveform.  You don't normally see a pure sinusoid and deviations from the pure sinusoid mean that there is other harmonic content in the waveform that is not in resonance and does its own thing.

TK:

I think the fancy coil patterns in old radios are related to their roll-off frequencies and stuff like that.  So indeed, that's a case of where it's by design for a particular purpose.  It also might not be true, and it's just a manufacturing technique.  I really don't know.

Pulling out the big guns, this guy is great and he really knows his radio circuits.  Radios are all about resonant circuits.  He also teaches a lot about electronics.  Plus, it's simply fun to see how things were designed and manufactured so long ago:

http://www.youtube.com/user/AllAmericanFiveRadio/videos?view=0&flow=grid

He does respond to questions in case someone wants to ask him about the herringbone coils.

Let me again share some thoughts about a self-resonating coil vs. an LC resonator, i.e.; two separate components.  The self-resonating coil is a kind of kludge.  You don't have a regular, ordered exchange between stored capacitive energy and stored magnetic energy.  They are intermixed with each other and if real push came to shove you would need a supercomputer crunching away to model it.  On the other hand, a LC resonator is smooth like butter.  The capacitor discharges into the coil, then the coil discharges into the capacitor.  The current flows back and forth, the voltage goes up and down.  That transfer of energy can be visualized as a rotating vector.  It's the way it's supposed to work.  In comparison to that a self-resonating coil is a different animal.  That's what I envision in my head.

Now realistically, if you scoped a self-resonating coil you would probably see a voltage waveform that was a sine wave across the ends of the coil.  At the same time it can only store a tiny fraction of the of energy of a comparable LC circuit - an inductor mated with a capacitor of comparable size.  I realize it's all relative to what you want to do.  I am just not sure what that is.  Nonetheless, a self-resonating coil is like a short faint wisp of stored energy at a crazy high frequency that disappears quickly compared to making a real loud and ringing LC resonator bell made with the same coil.

MileHigh

[MileHigh]

Magluvin:

This is what I like about the idea of the coil reacting quicker for a pulse motor. There will be more of an impulse than a gradual climb in current flow when the coil is being pulsed. We are talking 'pulse' motors. A quick pulse has more impact, impulse. It pops, no waiting period, no mooshy mooshy. Like using a small sledge hammer vs a rubber mallet of the same size.
Another thing is, lets say we have a simple pulse motor. 12v batt, normal coil, rotor with magnets and a reed switch. When we close the reed, it will take some time for the field to build due to impedance. And when it finally peaks or even sustains peak for the duration of the switch closure and the reed releases and waits for the next mag pass. But once we get to higher revolutions, the pulse times will be shorter with less time for the field to build. But the fast acting bifi will be able to react more quickly with more controlled on and off times and better high rpm performance.

The only way to get a faster reaction out of the coil is to increase the drive voltage.  The coil integrates voltage with respect to time to yield current.  How do you get a flywheel to spin up faster?  More torque.

Without increasing the voltage your impulse might charge some capacitance.  That will not give the coil any push against the rotor.  The only way to get the coil to push is to have it generate a magnetic field which leads back to the question of the drive voltage over time.

Your point about the higher RPM meaning less switch-on time and hence lower maximum current through the coil is dead on.  It's all part of the pulse motor finding a quiescent speed.  You can try to optimize stuff like Farmhand is doing and that's finding a higher quiescent speed.

The parameters are the amount of inductance, the switch timing, and the drive voltage.  Faster RPM by default limits the switch-on time, so you can experiment with the amount of inductance and the drive voltage to pump more power into the coil which pumps more power into the rotor to balance out the air and bearing friction.  Hence my fantasy of slowly cranking up the voltage to see what fails first.  Push the sucker past its design limits.

So the inductance is still a wall that you have to push against, series bifilar or not.

What we are going to do is use the reed to charge up the new large inductor and when the reed releases, let the collapse current of the large inductor dump into the motor driver coil to run the motor. But oh, the motor driver coil will not accept the collapse current due to impedance so the reed burns instead.

I will rephrase that as a question:  What happens when Coil A with current A discharges into Coil B with current B?

But if the motor driver coil is a bifi, even a big one, it will accept that collapse current, not the 'norm', which will charge that tiny capacitance of the bifi to possibly many hundreds of volts.

Exactly, but that won't push on the rotor!  But what happens after that and how does that relate to the question above?

MileHigh