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Old 07-23-2012, 09:03 AM
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lamare lamare is offline
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Bifilar wound coils - switch series/parallel?

There appear to be interesting effects when using bifilar wound coils:

Tesla Bifilar Coil patent - Bedini Bifilar Coil usage in Schoolgirl Radiant Motor Charging devices |

Figure 1 is a standard pancake coil (many Tesla coil builders are familiar with this style). Figure 2 is a bifilar coil, the crux of the patent is where Tesla winds a dual wire and then connects the ends in a series (an interesting experiment for coil builders).

Tesla explains that a standard coil of 1000 turns with a potential of 100 volts across it will have a difference of .1 volt between turns. A similar bifilar coil will have a potential of 50 volts between turns. In that the stored energy is a function of the square of the voltages, the energy in the bifilar will be 502/.12 = 2500/.01 = 250,000 times greater than the standard coil!"
Exotic Research | Vol 2 No 2 | New Generation of Radiant Energy Devices
Tesla's US Patent No. 512,340- "Coil for Electromagnets"- is a very special coil design because, unlike an ordinary coil made by turning wire on a tube form, this one uses two wires laid next to each other on a form but with the end of the first one connected to the beginning of the second one. In this patent Tesla explains that the double coil will store many times the energy of a conventional coil.

Measurements of two coils of the same size and with the same number of turns, one with a single, the other with a bifilar winding, show differences in voltage gain. These bifilar coils can be explained solely on the basis of their electrical activity. A bifilar coil is capable of holding more charge than a single wound coil. When operated at resonance, the distributed capacitance of the bifilar coil is able to overcome the counter electromotive force (emf) normal to coils - inductive reactance.

Because of the electrical activity, a bifilar coil does not work against itself in the form of a counter - emf, the potential across the coil quickly builds to a high value. The difference between the turns becomes great enough that the energy is practically all potential, at this point, the system becomes an electrostatic oscillator.

What is very interesting, is that there appears to be a stronger magnetic field when using bifilar coils, even when using D.C.:

Bifilar Electromagnet
The same amount of voltage, from the same battery, produces twice as much energy in the bifilar wound coil as in the single wound coil. This is just one of the many techniques Nikola Tesla used to make his inventions highly efficient.

If these interesting effects indeed have something to do with inter-turn voltage differences, then this could be very useful in parametric variation machines, because the bifilar windings can be switched from series to parallel at will. In series, you get additional inter-turn voltages, which you don't get when switched in parallel...
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