Tesla Bifilar Inductor

Bifilar coil - Wikipedia, the free encyclopedia

I saw that. What did I miss there?

I don't know that you missed anything. It's just a less cumbersome explanation of the device.

Patents are not written to fully disclose all the details of an invention. The Wiki article helps those less conversant in the field (such as myself) to understand what's going on.

Tesla's patent 521,340 has no technical value - perhaps historical value, showing that great inventors did make serious mistakes.

What he claims in the patent - that the additional capacitance between windings helps to neutralize the inductance of the coil is totally incorrect. He is constructing a "L-C parallel" circuit which will rezonate at some frequency and present a high impedance. Thus, the effect of the additional capacitance 'accentuates' the inductance of the coil - especially at and near resonance.

A BIFILAR inductor will have two starts and two finishes, . . . its performance will vary greatly depending on how you connect the two windings.

1. Each winding separately will have an inductance of "L".

2. If you connect the finish of one winding to the start of the other winding you will have an inductance of "4L".

3. If you connect the finish of one winding to the finish of the other winding, the inductances will cancell - result L = 0. Only the resistance of the windings remains.

Nikolay had connection #2 - where the inductance is increesd by 4. No cancellation of inductance whatsoever. Nikolay does not make a red cent from his invention.

Bifilar inductors have some great applications . . . like in LINE FILTERs . .

Here the inductor presents high impedance to common-mode signals (voltge) and a low impedance to normal-mode signals (voltage).

O.

"Self-resonance (XL=XC) was known to Tesla but he does not discuss the advantage of his invention with regard to resonant frequency, so I suppose resonant frequency is immaterial."

The bifilar coil proposed in this patent has significant parasitic winding capacitance which lowers the self resonant frequency into a range where it may be of some practical use. Tesla states (in the patent) the purpose of the invention was to reduce/eliminate the external capacitance necessary to obtain resonance at a desired frequency.

"His purpose was to neutralize the effect of self-inductance, at any frequency."

If Tesla wanted to neutralize self inductance at any frequency, he would have simply connected the bifilair coils so the currents flowed in opposite directions. Magnetic fields would cancel and self inductance (flux linkage) would be minimized.

My question is relating to a device with near field effects. The purpose is desalination. No signal transmission issues. I'm interested in the utility of the inductor of the Tesla design for pumping power into a conductive fluid with the fluid under shear.

The capacitance is for absorbing the back emf due to mutual induction between adjacent coils. The series winding geometry of the Tesla design introduces a potential between adjacent windings due to resistive loss through the length of the first coil. The coils are wound such that their currents go in the same direction, for maximum inductance when you are trying to cause an effect on a substance being hammered at RF (microhammered). The non-inductive geometry, where currents go in opposite directions, would solve the back emf problem at its source, but such a design would be weak for the microhammering application, in my opinion.