Tesla's "COIL FOR ELECTRO-MAGNETS".

[gyulasun]

I answer here to Magluvin, once Farmhand created this thread on the Coil for electromagnetc topic, quote from the Confirming the delayed Lenz effect thread:

We talked about the capacitance neutralizing the self inductance the other day.
If we have a coil with a cap across it, and then we just apply a dc source across it, the cap will charge virtually instantly, but the inductor wont. This might imitate a neutralizing of self inductance of the coil, where the current flows easily through the cap. We are talking about applying DC here.

If the capacitance is 'in' the coil, well that current that charges that capacitance goes 'through the coil' neutralizing the self inductance. And if it neutralizes self inductance, then maybe we could think, does that mean that the magnetic field is neutralized also, or just the effect of impedance is neutralized and outer magnetic field is unaffected. If so then initially there could be a very intense field pulse, as compared to a slowly building standard inductive field build, depending in the inductance.

That internal capacitance is charged through a coil that can make an external field like any other coil and the impedance is neutralized. So until this capacitance is charged, this coil might be acting like a super electromagnet. Sounds like a heck of an idea to patent.

If we consider the cap connected to a coil, there probably isnt any purpose for it in the DC world. But here the capacitance is in the coil, and in my opinion, there should be a difference.

Also I stated earlier about the ability of holding power over time. Well if the field is huge in the beginning through the object being held, this may give us that stronger hold over time, instantly instead.

So you can see why I am emphatic about not testing them in series. It is not conclusive in any way. It does not show if one coil could pull more current than the other with the same voltage input. Its not correct in any way. The only thing that does is possibly show that the 2 coils can pick up the same amount of clips. But the singlefi coil in series wont allow the capacitance of the bifi to charge as it would connected to the supply alone, thus no initial magnetic pulse from the bifi.

Will see soon.     Im going more is better.

Mags

Hi Mags,

I understand what you say. Basically I agree with it, the higher the self capacitance of a coil is, the more chance the input current 'sees' a less inductive reactance to fight with in the transient time till reaching the steady-state condition.  In my tests the about 420 uH bifilar coil with its 220 pF 'embedded' capacitance surely represents a negligible problem in this respect because these LC values are too small to cause any effect for the speed of a hand-operated switch I acted with.
There must be transient phenomenas in case of any RLC circuit / network but the switch on or off speed is important because the closer you hit the resonant frequency of an RLC circuit by the switching speed, the quicker the inductive (or capacitive) behaviour of the RLC circuit vanishes and the phase of the input current in that case will be closer and closer to the phase of the current flowing via the R part of the circuit.

This is exactly what Tesla achieved in his Coil for electromagnets patent by introducing wire B and winding very close to wire A, making up for the 1000 turn example of wire A with the additional 1000 turn of wire B. This way there have been an 'artificial' capacitor created and embedded into the coil when wires A and B were connected in series as he explained. He came up with this solution to increase the coils self capacitance without the use of high voltage discrete capacitors for lowering the normally rather high self-resonances of coils.

You ask: "does that mean that the magnetic field is neutralized also?"  By no means, because even for DC currents the capacitors represent a short circuit till they get charged up and for AC or pulsed DC currents the capacitors charge up then discharge as the rate of change dictates. AND the same input current must flow via the coil wires, especially in a series connection like Tesla showed. So the input current can go through the coil(s) hence flux is created.

I may have answered your questions.

Gyula

[synchro1]

Here's lidmotor broadcasting a radio signal with an upright pancake coil.


http://www.youtube.com/watch?v=hoKDU1yGkPo


Would a 1 Mhz radio broadcast signal power a neo magnet sphere, broadcast from a SB pancake coil transmitter like Lidmotors? 1 Mhz was designated the best power range frequency by Nicola Tesla. The magnet speed would have to be raised to synchronization speed independently to meld with the broadcast sine wave.

[gyulasun]

I quote again from the Confirming the delayed Lenz effect thread:

Quote from: synchro1 on April 21, 2013, 03:27:58 PM

Thank you Gyula. The original experiment involved  shorting both coils accross a "D" cell battery. The obvious difference between the experiments is that power is free to rise to load with the battery, unlike Gyula's latest try, where the power is governd. Maybe the bifilar electromagnet will draw more input then Gyula's inputing to it, if you feed it. The original experiment allows for increased current consumption compared to Gyula's generous attempt. Enlighting regardless!

Answer from Magluvin:
That makes sense. If the supply limits current then its possible that the low ohms of the 2 coils could push those current limits on their own, possibly not letting the currents needed bi the bifi to occur. Dunno yet.  But will.  (http://www.overunity.com/Smileys/default/wink.gif)

Mags   


Folks,

I do not fully understand you. The power supply does not limit current in my tests shown.  It is true that my supply has a controllable current limiting feature up to 750 mA max output current and it was set to that upper limit all the time.  And I took out only 430 mA from it. 
It is also okay that a D battery cell has a very low inner resistance but an analog variable power supply surely have a very low output impedance, normally the emitter follower power transistor output from its emitter point, so no problem in this respect. Power is also free to rise in case of a low output impedance supply too. 

Gyula

[TinselKoala]

(snip)
I strongly disagree with you though about using a square wave to find he coil self-resonant frequency.  We are modelling the coil as a parallel LC circuit and looking for the frequency corresponding to the the highest impedance, correct?  So why would you want to pump multiple simultaneous frequencies into the parallel LC filter if you are looking for a single resonant frequency?  When you characterize any filter it is easier to do it with a sine wave representing one frequency only, and then sweep that frequency.

I am not saying that it's absolutely wrong to use a square wave, but you could get fooled and see what you think is a peak response which is happening due to a harmonic and not due to the fundamental.  It's just "cleaner" to sweep the filter with a sine wave.

(snip)

You might be interested to know how my Arduino-based inductance meter works. I illustrate its operation in a video. I also show in another video how to determine the resonant frequency of a coil.

While the resonant frequency of a tank does correspond to the highest input impedance of the circuit, that is not the parameter I am observing, because that is not the parameter of interest. I want to know the resonant frequency. Hence I look for the purity and amplitude of the _output_ signal produced in a "receiving" coil placed around or near the inductor of the tank circuit I am testing. Take a look at Farmhand's scopeshots to see how the spectral purity of the output cleans up and becomes sinusoidal, and then peaks in amplitude, at the exact resonant frequency. There is no doubt when you get to the right frequency.

But the Arduino does it a little differently, but still corresponding to the same thing, and _still_ using a sharp-edged fast risetime square wave pulse to do it. The Arduino places the inductor under test into a tank circuit with a 2 microFarad cap, then rings the tank by applying a single sharp pulse, then it isolates the tank and observes the ringdown voltage peaks, times them and determines the frequency, then finds the inductance by calculation. A tank rings down at its resonant frequency, and the higher the Q the more countable peaks you will get in the ringdown before you have to "hit the gong" with a sharp pulse again.
(But of course a properly resonant TC hits the gong on every cycle in exactly the right timing.)
http://www.youtube.com/watch?v=S6N8ys8FiA4
http://www.youtube.com/watch?v=alkfoX62Na0
Any Tesla coiler knows that the key to getting the proper HV VRSWR effect happening in the secondary, is to make the "driving pulse" in the primary to have the most rapid rise and fall times possible: a rectangular pulse, not a sine. This is why Tesla spent so much time on spark gaps, and why the spark gap is so critical to a proper performing TC. And it's why my MOT DC SGTC works so well: I use compressed air to blow out the spark gap, to decrease the rise and fall times of the primary current.

ETA: Looking at the tank directly, as in the videos above, rather than using a second pickup coil, produces the same results but for slightly different reasons.

[TinselKoala]

I believe the SB coil broadcasts on a magnetically resonant bandwidth, broadcasting a pure sine wave signal in the Mhz range as the coil powers up. This is transformed into kinetic energy by the neo magnet. This is because the magnetic L C frequency of the coil grows to match the frequency of magnetic oscillation in the magnet spinner field, determined by strength. Then the magnet spinner catches a tail wind!

Not too much to object to there; your metaphors aren't leading you too far astray. All RF is "magnetically resonant bandwidth" for some receiver configuration, after all, and it is the neo magnet that is spinning, so no problems there, and certainly frequency matching is important and affected by the speed of the spinning magnet, and "catching a tailwind" is an appropriate way to describe the pumping of energy into the kinetic system, just as "pushing the child's swing" is. Weird kind of circular, cyclinc tailwind, though.