That observation leads us to a third important point:Making the primary resonant at the same frequency as the secondary is important for efficient generation of the one spectral component that matters.

Let’s take a look at these one at a time.First, a Tesla coil’s primary needs to be driven by a signal with spectral components at the same frequency as the resonance of the secondary. Since it sounds as if you are not using any tuning capacitors in the primary circuit of the Tesla coil, you’re relying on adjusting the spark gap spacing to hit the resonant frequency of your fixed secondary. A bit of light oil is floated on top of the water to eliminate evaporation, and insulate the conductive water from the varying amount of water vapor in the air, which affects overall capacitance.I’ll talk more about my designs, if anyone asks for it; do not hesitate to do so! jocularEdit: (red) There is essentially no resonant circuit in the primary, as no significant capacity exists in it, only inter-electrode capacitance of the transformer used as a voltage source. Originally Posted by jocular Originally Posted by tk421 Originally Posted by DBitty For a physics project, my group and I are building a 2 foot tesla coil. we’ve got a nice spark gap, and there’s current going through our primary coil, however, there’s nothing going through our secondary.

Our main concern though, is that our spark gap quits sparking after just a few seconds, then our nst makes a low buzzing sound. didn’t know what to think about that until we heard it bubbling on the inside and it started smoking. umm yeah. any help would be appreciated. The need for loose coupling is why all photos of real Tesla coils (as built by Tesla, as described by Tesla, and as prescribed by Tesla) show a large spacing between the primary and the secondary.You don’t have to take my word for this. Luminous tube transformers provide a good starting point for this purpose, as they are available with output voltage of 15,000, with primary voltage needed 120. It is not driven by a pure 60Hz sinusoid, by your very own description. There are several misconceptions in your post, ranging from your definition of a Tesla coil, to a general ignorance of how coupled resonators work, and a neglect of what the spectrum of an interrupted “60Hz” drive signal looks like. Okay, Okay, I relent! But please, explain to me if given a transformer, single-phase, 120 V primary, 15 KV secondary, regulation being such that the secondary will deliver harmlessly 50 MA while short-circuited (typical gaseous tube transformer for lighting use), and I place a spark gap in series with the secondary, such that it’s short-circuit current flows back and forth through the gap at 60 HZ, what capacitance is present capable of producing harmonic frequencies of reasonably useful amplitude? jocular These are often a trouble spot.

Period. It acts much like a modulator, actually, interrupting the 60Hz mains power at a rate determined by a combination of the breakdown voltage and the reactances connected to the spark gap (it’s perhaps more intuitively appealing to say that the 60Hz mains power modulates the spark gap current). Luminous tube transformers provide a good starting point for this purpose, as they are available with output voltage of 15,000, with primary voltage needed 120.

The “60Hz” signal is just the fundamental component, and is more or less just there for the ride. Only the spectral component at the resonant frequency of the secondary does anything useful in a Tesla coil. umm yeah. any help would be appreciated. The top electrodes are connected together, while the outer “electrodes”, the foil, are all connected via the salt water.

The top electrodes are connected together, while the outer “electrodes”, the foil, are all connected via the salt water. First, stop the smoking.You won’t get anything out of the secondary unless it’s tuned to the same frequency as the primary. A bit of light oil is floated on top of the water to eliminate evaporation, and insulate the conductive water from the varying amount of water vapor in the air, which affects overall capacitance.I’ll talk more about my designs, if anyone asks for it; do not hesitate to do so! jocularEdit: (red) There is essentially no resonant circuit in the primary, as no significant capacity exists in it, only inter-electrode capacitance of the transformer used as a voltage source. I am using the definition provided by Mr. If tightly coupled, the resonances are significantly perturbed, leading to a splitting of mode frequencies, and lousy Tesla coil operation. It may be some other kind of coil, but it ain’t a Tesla coil. I use 12 oz. beer bottles filled with salt water, an electrode reaching down into it, the bottles being wrapped with aluminum foil on the outside, about half-way up; the bottles are then stood upright in a plastic basin having about 5 inches of salt water in it.

And the primary, of course, must be loosely coupled to the secondary, otherwise it will be impossible to get two synchronous resonances. Originally Posted by tk421 Originally Posted by jocular Okay, Okay, I relent! But please, explain to me if given a transformer, single-phase, 120 V primary, 15 KV secondary, regulation being philosophy essay writing
such that the secondary will deliver harmlessly 50 MA while short-circuited (typical gaseous tube transformer for lighting use), and I place a spark gap in series with the secondary, such that it’s short-circuit current flows back and forth through the gap at 60 HZ, what capacitance is present capable of producing harmonic frequencies of reasonably useful amplitude? jocular Without knowing all the details of your configuration, all I can do is make some guesses. All of the other components represent waste, essentially. To make things simple, start with two identical resonators and derive the eigenmodes as a function of coupling.

And the primary, of course, must be loosely coupled to the secondary, otherwise it will be impossible to get two synchronous resonances. If the voltage source of the primary is 60 HZ, and the secondary resonates with it’s capacitance at perhaps a million HZ, then obviously there is a vasr frequency difference.The idea is for the spark gap to interrupt primary current flow, like a switch, which allows time between “switchings” for the collapsing primaryy field to induce a voltage across the secondary coil many, many times higher, due to the turns ratio between the coils. Our main concern though, is that our spark gap quits sparking after just a few seconds, then our nst makes a low buzzing sound. didn’t know what to think about that until we heard it bubbling on the inside and it started smoking. umm yeah. any help would be appreciated. That observation leads us to a third important point:Making the primary resonant at the same frequency as the secondary is important for efficient generation of the one spectral component that matters. You can derive for yourself the equations for the mode frequencies of coupled resonators. Thus, the primary “kicks” energy into the secondary relatively slowly, compared to the resonating “tank” circuit formed by the secondary inductance and it’s paralleled high-voltage capacitors, which resonate at extremely high frequency. It’s not hard, just a little tedious (but not so much so that my freshmen can’t handle it with a little prodding).

Originally Posted by tk421 Originally Posted by DBitty For a physics project, my group and I are building a 2 foot tesla coil. we’ve got a nice spark gap, and there’s current going through our primary coil, however, there’s nothing going through our secondary. What does the actual work in a Tesla coil is not the 60Hz energy, but the higher-frequency components associated with the spark-gap-interrupted waveform. Again, you don’t have to resonate the primary, but then you don’t have a Tesla coil, and efficiency will be poor.Finally, if you couple two resonant systems together, whether you end up with a synchronously tuned fourth-order system (which is what a Tesla coil is, to a lumped approximation) or not, depends very much on the coupling strength. That can be made to work, after a fashion, but you’d get much more impressive results if you were to tune the primary explicitly, rather than relying on parasitic effects. First, stop the smoking.You won’t get anything out of the secondary unless it’s tuned to the same frequency as the primary.

How are you measuring/tuning the resonances? This may not be quite right. And the primary, of course, must be loosely coupled to the secondary, otherwise it will be impossible to get two synchronous resonances. Originally Posted by jocular Okay, Okay, I relent! But please, explain to me if given a transformer, single-phase, 120 V primary, 15 KV secondary, regulation being such that the secondary will deliver harmlessly 50 MA while short-circuited (typical gaseous tube transformer for lighting use), and I place a spark gap in series with the secondary, such that it’s short-circuit current flows back and forth through the gap at 60 HZ, what capacitance is present capable of producing harmonic frequencies of reasonably useful amplitude? jocular Without knowing all the details of your configuration, all I can do is make some guesses. That was the key contribution by Tesla — he showed how to convert low-voltage, low-frequency mains power to high voltage at a high frequency. If the voltage source of the primary is 60 HZ, and the secondary resonates with it’s capacitance at perhaps a million HZ, then obviously there is a vasr frequency difference.The idea is for the spark gap to interrupt primary current flow, like a switch, which allows time between “switchings” for the collapsing primaryy field to induce a voltage across the secondary coil many, many times higher, due to the turns ratio between the coils.

If you are using a standard NST, there is a significant amount of leakage inductance and capacitance associated with its own secondary windings, so there is a definite resonant frequency associated with the NST itself.The spark gap does interesting things to the spectral content of the current. Tesla himself.Second, let’s look at how the primary is driven. Let’s take a look at these one at a time. I use 12 oz. beer bottles filled with salt water, an electrode reaching down into it, the bottles being wrapped with aluminum foil on the outside, about half-way up; the bottles are then stood upright in a plastic basin having about 5 inches of salt water in it. If you do not satisfy that requirement, it is not a Tesla coil. How are you measuring/tuning the resonances? You can make things easier on yourself by recognizing that you can readily identify one eignemode with a common-mode (even-mode) excitation, and the other with a differential-mode (odd-mode) excitation. Either electrostatic or magnetic coupling will show what you want to show.

First, stop the smoking.You won’t get anything out of the secondary unless it’s tuned to the same frequency as the primary. Originally Posted by tk421 [There are several misconceptions in your post, ranging from your definition of a Tesla coil, to a general ignorance of how coupled resonators work, and a neglect of what the spectrum of an interrupted “60Hz” drive signal looks like. These are often a trouble spot. Thus, the primary “kicks” energy into the secondary relatively slowly, compared to the resonating “tank” circuit formed by the secondary inductance and it’s paralleled high-voltage capacitors, which resonate at extremely high frequency.

How are you measuring/tuning the resonances? This may not be quite right.

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