Conrad:

When you add more turns to a series bifilar coil, you get more inter-coil voltage and more capacitance.  However, you are also getting more inductance.  It's the relative proportions between the inductance and capacitance that define a characteristic of the coil.  The coil gets bigger and the resonance frequency goes down.

In terms of relative proportions, the inductance remains the elephant, and the capacitance remains the fly on the back of the elephant.  The elephant and the fly get larger and smaller in tandem, and their relative proportions remain about the same. It's the same thing in real life.  A small stiff metal spring self-resonates at a high frequency.  A larger much much stiffer metal spring also self-resonates, but at a lower frequency.  There is an (electrical <-> mechanical) analogy that goes both ways.

Looking forward to see what you do next.

MileHigh

Normal coil  100 turns 100v  1v between adjacent turns
Bifi coil         100 turns 100v  50v between adjacent turns

Normal coil   1000 turns 100v .1v between adjacent turns
Bifi coil          1000 turns 100v  50v between adjacent turns

Normal coil    2 turns  100v 50v between adjacent turns
Bifi coil           2 turns  100v 50v between adjacent turns

The more turns a normal coil is, the less significant its capacitance becomes as the potential difference becomes less and less between the adjacent turns, and between these adjacent turns is where the capacitance is.

Normal coil   5000 turns, 1kv  .2v between adjacent turns
Bifi coil          5000 turns  1kv  500v between adjacent turns.

How many people reading here can realize the difference?     Charge a small cap with .2v and charge a larger cap with 500v.  We all should know the difference between what .2v and what 500v can do into the same resistance, or even an inductance. 2 coils, same turns, same dimensions, same wire. Just wired differently.

Mags

Quote from: conradelektro on January 13, 2014, 03:49:34 PM
@Farmhand: thank you for taking the time to explain. I think you read the patent correctly, it says just that. But one has to read attentively and with some background knowledge to get it.

Just to check that I understood correctly I make up a hypothetical example.

Let's take my two pan cake coils (the monofilar has a self capacitance of 9 pF and the bifilar has a self capacitance of 45 pF):

- the supplied or applied frequency is 4 MHz (I just make that up to have an example)

- in order to "power factor" correctly we have two possibilities:

A) we take the monofilar pan cake coil and add a 36 pF capacitor (9 + 36 = 45 pF) so that it resonates at 4 MHz

B) we take the bifilar pan cake coil which is in resonance with 4 Megahertz without adding any capacitor because its self capacitance happens to be 45 pF

- Alternative B) is cheaper because we do not need to buy a capacitor.

- if the supplied or applied frequency were 2 MHz we would need a capacitor for both of my pan cake coils in order to "power factor" correctly (from my many experiments with my pan cake coils I happen to know that we need a 100 pF cap for the monofilar and a 74 pF cap for the bifilar pan cake coil to make them resonate at 2 MHz)

Greetings, Conrad

That's how I'm seeing it. I think as MileHigh says a coil excited to parallel resonance unloaded and without losses will have an infinite impedance, however A coil excited at it's frequency where the Capacitance cancels the Inductance effects when under load would not actually be excited to resonance, just excited at the frequency of resonance, not into resonance.

I think there is a miscommunication on that. As long as the reactive power is taken into the capacitor, turned into activity and does not return to the supply there is an advantage. This is well known.

Also if the coil is at resonance with it's own L/C then no currents should go back, only the losses are replaced with real power and so the false currents are mostly removed.

Yes going by the text it says the getting rid of false currents and efficiency is the object. And any coil will do the same thing.

An electromagnet is any conductor with a current flowing through it. No kidding. Tesla includes all coils in the patent as an example of the effect of the capacitance to the inductance.

So all coils which see current are electromagnets, and the patent is about winding the coils so that when the coils are excited at the correct frequency the "effects" of self induction are cancelled, not the self induction itself, that is not cancelled only the unwanted effects of it.

..

A simple explanation of the two resonances.

In parallel LC resonance the impedance is infinity and no current flows.  So that means as the source AC voltage varies and wants to put current through the circuit, the capacitor is "pushing back" with exactly the same voltage and no current can flow.  As the source voltage drops, the capacitor voltage drops in tandem and is an equal and opposite mirror to the source voltage.

The capacitor "knows" that when the AC voltage drops below zero, it still has to "fight back" and resist the application of negative voltage from the source.  So where does the capacitor get the means to generate the equal and opposite voltage?  The answer is that the capacitor stored some energy in the inductor.  As the source voltage drops below zero the capacitor starts to "drain" the inductor of energy and accumulate the required voltage to fight back.  Or more accurately, the inductor is pumping up the voltage in the capacitor so that it has the means to fight back.

So you can look at the parallel LC circuit in resonance like a small amount of energy that cycles back and forth between the capacitor and the inductor that effectively blocks the circuit.  It fights back with the equal and opposite voltage and no current flows as a result.

Too tired for the explanation for series LS circuit in resonance.

MileHigh

Well that pre-supposes that the energy remained in the L/C and there is no load. Does it not ?

If the energy is dissipated then the supply should see an empty capacitor not the Inductance.

We are talking about when the current flows not when it does not flow.

Similar to the "resonance" per se as in an Induction cooker I think.

OK then can you draw us a test circuit to excite the coil to series resonance then please ?

I'll guess the capacitor is just in series with the input, simple I'll try to find my original small coil set and do that.

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