Russ,
I've been interested in the WFC project for about a day or so and I'd like to make a few comments for the benefit of the team. I trust that you don't find this to be too presumptive.
Firstly, nomenclature is important because it conveys detail to the reader. Much of Stans work is deliberately obfuscated so you must read between the lines.
The bifilar wound coil is not a choke; rather it is an electrostatic oscillator. This was first described by Tesla around the late 1800s.
You will find that most wire wound resistors are formed this way in order to minimise inductive reactance. The windings are essentially 180 degrees out of phase, which more or less cancels out any inductance.
The bifilar coil also exhibits a very low inductance value due to the cancellation effect, regardless of the fact that it is formed around a high permeability core.
However, the device exhibits a high interwinding capacitance, which with the stray inductance forms a resonant circuit at some frequency.
Let's recap shall we:
An inductor stores a charge in its magnetic field and when the magnetic field collapses the stored EMF (not voltage) collapses it induces an opposing current into the circuit.
A capacitor stores electrons in its electrostatic field (not current). When the electrostatic field collapses (discharges), electrons are released which tends to maintain the voltage.
In essence then, the bifilar wound coil looks more like a capacitor that doesn't block DC than an inductor. However because there is some inductance the device will resonate but it cannot oscillate due to the blocking diode - hence its name.
At resonation the voltage builds with each pulse, which if left in the on-state for a period, would cause the coil insulation to break down. Effectively, we are delivering a controlled rising amplitude pulse train to the load and you will notice that the voltage rises and then starts to fall in accordance with the Time Constant of the FET circuit.
The next pulse raises the voltage further until the capacitor (bifilar coil) is charged up and the decay process repeats.
When the frequency is changed, notice that the time is lengthened or shortened but the waveform remains the same. That's because the only thing that really changed was the FET controlled Time Constant.
Further notes:
When winding bifilar coils it is absolutely essential that the distance between the windings (if any) is kept as constant as possible across the whole coil. Any significant variance will affect your ability to reproduce any model you do get operational.
At the relatively low frequency required for this system, don't pay too much attention to skin effect in the calculations
There is some question about the AWG29 quoted for this device. Since we know that the device is being used as a voltage amplifier (intensifier unobfucsated) it is very likely that multi-coated wire was used to increase reliability. It's also likely that the polymer coating used 25 years ago was thicker as it may have been less capable. If problems become apparent the solution will be to add a few extra turns on to the coil because the interwinding capacitance will be somewhat lower.
Jon,
Capacitors in Series: (1/Ctotal) = (1/C1) + (1/C2) + (1/C3)...
Capacitors in parallel: Ctotal = C1 + C2 + C3...
Inductors in series: Ltotal = L1 + L2 + L3...
Inductors in parallel: (1/Ltotal) = (1/L1) + (1/L2) + (1/L3)...
Resistors in series: Rtotal = R1 + R2 + R3...
Resistors in parallel: (1/Rtotal) = (1/R1) + (1/R2) + (1/R3)...
Hope this helps
Cheers
Peter
Additionally the EEC in the upper coil part in parallel to the coil makes a major change for resonance behaviour because it can shortcut the upper bifilar wound coil.
bussi04
Hi,
I'd like to comment on this statement from 42n8 and may be collect feedbacks from all of you:
"The windings are essentially 180 degrees out of phase, which more or less cancels out any inductance.
The bifilar coil also exhibits a very low inductance value due to the cancellation effect, regardless of the fact that it is formed around a high permeability core."
Based on my understanding this is key to replicate Stan's job and it's probably the reason why many of us failed to achieve resonance; the reason was not the VIC circuit and components parameters but rather the VIC transformer and to be specific the way the two inductors were wounded or connected to the cell. Both Jon and recently Russ in their posts used windings 180 degrees out of phase; Jon's PWN is very basic (no PLL) but he found resonance and I could say the same for mine PWM so this seems to confirm the tricks are in the magnetic circuit and not really in the electric one. This was not clearly explained in Stan's patents but I'm convinced this is the way it should work also because we can clearly trace Stan's job back to what Tesla did in the end of 1800.
Jul.