Just a question for the EE guy's here.
When we make a tank circuit,such as Rick is doing with all his coil's (TX and RX),do we not loose half the energy charging the cap each half cycle? I mean,if the potential energy =U = qV,and as the charge reaches the capacitor, energy stored become's Uc = (1/ 2) qV,this means that the loss in energy = U - Uc. So 50% of the energy is lost during each half cycle--as heat i would expect.
So,when we inject a pulse of current into a tank circuit,and we see that circuit ring down,is it due to loosing half the energy each half cycle to charge the cap?
It would seem to me that it would be more efficient not to have a cap in series or parallel to the coil,and just pulse the coil by itself at the right frequency. I mean,the coil will already have some self capacitance,so why add more losses by adding an additional capacitor ?.
Brad
In a tank circuit the inductor is a current source, not a voltage source. As such it charges the capacitor with zero loss and in an ideal simulation it does not ring down but can continue indefinitely. Try a simulation using zero loss inductors and capacitors and you will see. In the real world the losses are the resistance of the coil, the dissipation factor of the capacitor, (and radiated losses when the tank operates at a frequency where it can efficiently couple to the air), which can be minimal if designed with high quality components such as vacuum capacitors (very low dissipation factor) and the coil will be made with as low a resistance as possible. You are correct that that some of the losses are from heat as outlined above, but this is because the components are not ideal and have resistance and a dissipation factor. If you study how high power transmitter tank circuits are constructed, you will understand what must be done to minimize losses. Look in the ARRL handbook for more info on this. The point is, a well designed tank coil will have a very high Q and the damping ratio will be low. https://en.wikipedia.org/wiki/Q_factorhttps://www.google.com/search?q=damping+ratio+formula&ie=utf-8&oe=utf-8&client=firefox-b-1https://en.wikipedia.org/wiki/Damping_ratioBy the way you posed the question for an EE, well, I'm not a formal college educated (4 years) EE, but in addition to some 3 years technical school, and supplementary courses, I have had around 60 years hands on experience in the real world designing power equipment, sophisticated analog and digital circuits and microcomputer controlled process equipment, where I had to teach myself most of this stuff. Most of the equipment I designed is still being sold today 21 years after I retired from that industry, and making millions for my former employer, of which I get 0, I'm just not a good businessman. I know partzman's resume would be similar, as he also has designed numerous successful electronic devices and also has patents. I'm just a roll my sleeves up, hit the bench, consult the books when needed, and "git her done" kind of guy. I think this and other topics should be moved off the Rick video thread, as I'm sure he will be cut and pasting our info into his latest book for profit.
« Last Edit: 2019-07-25, 16:35:02 by ion »
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