The bifilar pancake coil at its resonant frequency

[TinselKoala]

@Citfa,

You started this problem with me over a year and a half ago when Whoppyjump asked for an explanation of "Flyback". I explained to him back then that positive current goes into the coil, then when the input current's interrupted, the magnetic field collapses and negative current goes out.

You contacted Stephan in Berlin and asked him to lock the thread down. Now just what in the hell is your problem? What is it that you fail to understand about my explanation? Why is it impossible for you to comprehend that?

You advanced your totally preposterous theory that "Negative Current" is imaginary. That's why you're constantly berated by me!

Doubling down on a losing hand AGAIN?

The "problem" here is that you don't understand your chosen topic, and your "explanations" are bogus, simply wrong. When the magnetic field collapses in a coil, the current continues in the SAME DIRECTION out of the coil, driven by the magnetic field's collapse. We have been over and over this, you have been presented with many references and demonstrations, but you persist in your easily falsifiable claims.

Why is there a "flyback diode" across a relay coil? Why do the LEDs behave as they do in my demonstrations? Why do Mile High, Cifta, TinMan, and every other knowledgeable poster here agree on this issue, but you don't?  It is because you don't know what you are talking about.

"Negative current" is your misnomer for CURRENT flowing one way, "Positive current" is your misnomer for CURRENT flowing the other way. CURRENT in wires is the flow of CHARGE, that is, the NEGATIVE UNIT CHARGE carried by electrons. The AMPERE is the unit of CURRENT, and it is measured in COULOMBS of CHARGE per SECOND. 

[Magluvin]

Okay, so let's use Conrad's numbers for his series bifilar pancake coil from his second clip and make some inferences.

His numbers:  34 microhenries, 49 picofarads of self-capacitance and a 3.9 megahertz self-resonant frequency.

We know that air typically breaks down at 20 kilovolts per centimeter.  Let's assume the spacing between turns is one millimeter and we will simply ballpark the breakdown though the insulation as 4 kilovolts.  In other words, we are doubling the air breakdown to factor in the insulation.

Max energy stored in the self-capacitance (at peak voltage):  E = 1/2 * 49 pF * (4 kV)^2 =  392 microjoules.

How much current does that correspond to (at peak current):  i = sqrt ((2*E)/L) =  4.8 amps

So the RMS current through the self-resonating coil would be on the order of 4.8/1.414 = 3.39 amp RMS

So if we assume a 10-ohm coil the power dissipated would be on the order of 3.39^2 x 10 = 114 watts.

Obviously it is not realistic to have a hand-sized self-resonating pancake coil dissipating about 114 watts.  So let's scale everything down to 10 watts dissipation.  So the RMS current has to be about one amp and the peak current 1.414 amps.  So the inductive energy becomes 34 microjoules.  That translates into a peak capacitance voltage of 1178 volts.

That seems pretty realistic.  You have a fairly hot pancake coil self-resonating at 2356 volts peak to peak, storing 34 microjoules of energy and you are feeding about 10 watts of continuous power into it by some means to keep it resonating at 3.9 megahertz.

So the questions must be asked:  SO WHAT, and WHY?

Why would I want to store a measly 34 mircojoules of energy in a resonant cavity blazing away at 3.9 megahertz when I have to continuously pump 10 watts into the series bifilar pancake coil to sustain the resonance?

What precisely is that going to do for me?

First I have to say that you simply interpreting that the coil is 10ohms gives your offering whatever outcome you are trying to convince others of.

Why cant the coil be 1ohm? or even .5ohm? Clearly he is not using wire that would have a 10ohm outcome. Looks to be 18 to 20ga, where 10ohms on that would mean he is using some resistive wire of sorts. Im only pointing that out as you used his 34uh coil and 49pf in your example. Saying or say, assuming his coil is 10ohm just by looking at it is a pretty big misstep in my opinion and using that 10ohm example changes what the actual outcome that you show and id say its totally misleading. Take another look at those coils. Did he say they were 10ohm? How many feet of wire do you think are on those coils? lets say that we can agree that the wire looks to be even 20ga. Do you still 'feel' that the resistance would be anything close to 10ohms? When you buy a cheap stereo system for the home and it comes with 2 10ft roles of say 20ga wire and the speaker is, now a days, 4ohm, what would 10ohms of resistance in the wire do to the outcome of the speaker output?

I just measured a 100ft roll of 18ga wire. 100ft!  1.4ohm     So would you say that his coils look like there is 700ft of wire there?

Now, if the coil did have 700ft of wire in order for the resistance to be 10ohm, then that completely changes the outcome of the inductance AND capacitance of which you are using in your example, big time. So you may need to rewrite you thesis on that one.


You say that he is feeding the coil 10w to keep it going at resonance. In my experience, at resonance the input is largely minimized. Where did you get that number??

Mags

[Magluvin]

Doubling down on a losing hand AGAIN?

The "problem" here is that you don't understand your chosen topic, and your "explanations" are bogus, simply wrong. When the magnetic field collapses in a coil, the current continues in the SAME DIRECTION out of the coil, driven by the magnetic field's collapse. We have been over and over this, you have been presented with many references and demonstrations, but you persist in your easily falsifiable claims.

Why is there a "flyback diode" across a relay coil? Why do the LEDs behave as they do in my demonstrations? Why do Mile High, Cifta, TinMan, and every other knowledgeable poster here agree on this issue, but you don't?  It is because you don't know what you are talking about.

"Negative current" is your misnomer for CURRENT flowing one way, "Positive current" is your misnomer for CURRENT flowing the other way. CURRENT in wires is the flow of CHARGE, that is, the NEGATIVE UNIT CHARGE carried by electrons. The AMPERE is the unit of CURRENT, and it is measured in COULOMBS of CHARGE per SECOND.

I am in total agreement on the fact that the field collapse generates a current in the same direction of the input that built it. Could someone misinterpret a scope shot, seeing the voltage differential change at the time of input connect then disconnect as a current reversal? Maybe thats the bungle here?

Mags

[tinman]

@Tinman,

Please answer the question:

What amount of power would be required to generate 1 Tesla of magnetic flux density in an "Inductor Coil" with a measured inductance of 1 Henry?

As MH said,your question makes no sense.

The Tesla is a measure of magnetic field strength-not magnetic flux density.

It's no wonder no one wants to answer your questions--they make no sense.


Brad

[tinman]

@Citfa,

You started this problem with me over a year and a half ago when Whoppyjump asked for an explanation of "Flyback". I explained to him back then that positive current goes into the coil, then when the input current's interrupted, the magnetic field collapses and negative current goes out.

You contacted Stephan in Berlin and asked him to lock the thread down. Now just what in the hell is your problem? What is it that you fail to understand about my explanation? Why is it impossible for you to comprehend that?

You advanced your totally preposterous theory that "Negative Current" is imaginary. That's why you're constantly berated by me!

For the last time--no it dose not.

The current flowing out of the coil,when the source current is interrupted,is in the same direction it was when the source current was connected.

Please try and get this through your head,as you are the one spreading miss information with your negative current rubbish.


Brad