The bifilar pancake coil at its resonant frequency

[Grumage]

Grum, thanks for posting that nice large famous photo of St. Nick sitting next to his big flat coil.

The scale of the photo makes it easy to trace the turns outward from the center.

So is it bifilar, or not?   

Dear TinselKoala.

You're most welcome.

Now, is that a hint that it needs re sizing ?   

Cheers Graham.

[MileHigh]

If only someone could come up with a practical real-world application for a series bifilar pancake coil.  It appears that they can't.  In my opinion this is all just a bunch of fuss over a Tesla patent that was never even used in anything.  I will remind you that the wording of the patent clearly states that the coil is supposed to be used for power factor correction because of the capacitance associated with the coil.  Power factor correction is real, but nobody is using series bifilar pancake coils to do it, they use capacitors.

It's just like a Bedini motor, the only practical application for it would be to power it with a wall wart, and use the motor to charge a battery.  There is no point in powering it with a battery.  And using a 555 timer with a transistor and a coil will give you a simple inductive-pulse battery charger that will outperform any Bedini motor.

I am just posing the uncomfortable issues to make you think.  If you just want to play with some coils on your bench then fine, play with a series bifilar pancake coil or a Bedini motor, just don't expect anything amazing to happen.

And of course there is a real-world analysis that could be done that I seriously doubt anybody is going to touch.  That being compare a series bifilar pancake coil with a plain ordinary cylindrical solenoid coil.  No fancy bifilar anything, just an ordinary solenoid coil.  The ordinary solenoid coil will outperform the series bifilar pancake coil in just about any application that you can think of.

The only place I am aware of where they use pancake coils, and I mean regular pancake coils and not bifilar pancake coils, is in kitchen ranges with induction cooktops.  There is no "magic" here at all, they use a flat pancake coil because its geometry is the shape of a flat pancake, and that's what they need.

<<< Induction cooking heats a cooking vessel by magnetic induction, instead of by thermal conduction from a flame, or an electrical heating element. Because inductive heating directly heats the vessel, very rapid increases in temperature can be achieved.

In an induction cooker, a coil of copper wire is placed under the cooking pot and an alternating electric current is passed through it. The resulting oscillating magnetic field induces a magnetic flux which repeatedly magnetises the pot, treating it like the lossy magnetic core of a transformer. This produces large eddy currents in the pot, which because of the resistance of the pot, heats it.

For nearly all models of induction cooktops, a cooking vessel must be made of, or contain, a ferromagnetic metal such as cast iron or some stainless steels. However, copper, glass, non magnetic stainless steels, and aluminum vessels can be used if placed on a ferromagnetic disk which functions as a conventional hotplate.  >>>

[Grumage]

Dear MileHigh.

Whilst I agree with your sentiments, there must have been " some " reason for Tesla to have built a coil of that size. Does anyone know ?

In answer to TinselKoala, I have drawn two Yellow lines, the coil seems to end in the centre with a pair.

Cheers Graham.

[evostars]

Dear evostars.

Is that one of R M Cybernetics PWM's you're using ?

yes,  it is indeed. works great.

I think the reason tesla made his coils so big,  is because he used high voltage.  the distance between the windings prevents sparks. 

[TinselKoala]

Grum, thank you for muddying the waters again. Perhaps you would take another look,
this time with your glasses on.

Start anywhere, follow the wire around the coil and see where you end up.