Author Topic: Bifilar coil  (Read 12212 times)

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Re: Bifilar coil
« Reply #40 on: April 24, 2014, 23:35:04 pm »
Well this conversation is just going on and on...
Lets make it simple..

2 coils of = wind on a core with opposite currents of equal magnitude will not create a magnetic field.. which means no inductance.. having only the impedance of the coppers resistance.

if the currents are unbalanced and one is more than the other then you will have a inductance by the higher magnitude current carrying coil..

if currents are in the same directions for the 2 coils then they both contribute to the total B field generated in the core..

If the winds are not equal and the gauge is not the same for the 2 coils then you run into more complexity for determining which coil will produce a higher H field for a given amount of amps through the coils.

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Re: Bifilar coil
« Reply #41 on: April 24, 2014, 23:40:19 pm »
it's not as simple as that but I can be wrong well the magnetic field is stronger the closer you're in the center ... and yes things start to get complicated here but it's not as simple as adding the fields... I suggest you try it..

 I don't know what but something is fried for sure.. although I get voltage readings from the pwm output and I have a snubber for bemf... anybody knows more about this? now there's nothing when I connect the self cancelling coil and when I connect regular pancake coil it goes up to 0.2V output and it went more before I now don't hear the buzz either...  :-\

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Re: Bifilar coil
« Reply #42 on: April 25, 2014, 02:44:45 am »
magnetomotive force (mmf) = 0.4 * pi * number of turns * amps

H field = mmf/ magnetic path length (MPL)

H =  (0.4 * pi * number of turns * amps) / MPL

so here we see H field (magnetizing force field) is all about transformer dimension, number of turns and amps

B = permeability * H

and here we see B field (magnetic field) is based on core characteristics (perm) and H intensity..

permeability is the measurement of how much H is needed to make x amount of B
higher perms means the B field intensity increases more with less H  field input

EMI filters used in all modern day electronics is a filter used right at the input  of raw AC mains power for  the electronic device. typically following a emi filter is transient suppression then on to rectification to create around 180v DC

The EMI filter is 2 identical coils on one core.. that has opposite currents.. it is used to filter out imbalanced currents that typically come from radio interference.. the imbalanced current is typically HF and it encounters inductance since the imbalance trys to make a magnetic field the inductance shunts the current (filters the noise).. the balanced current does not experience inductance and only feels the resistance of the copper.. a EMI filter is a perfect example of what happens with opposite currents and what happens with imbalanced currents since its job revolves around that..


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Re: Bifilar coil
« Reply #43 on: April 25, 2014, 13:50:59 pm »
Outlawstc is correct the field is zero inductions is zero. Now i see what are you doing geon.

Basically you  have coils not canceling perfectly so they keep some inductance.

If you use a core it can be made to canceling more perfectly...

The idea of this thread was to discuss about the bifilar coil...

So maybe we could get back to that...


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Re: Bifilar coil
« Reply #44 on: April 25, 2014, 15:35:39 pm »
My idea about the bifilar coil is that it acts like a sort of transformer but it works by one coil inducing in the other opposite voltages such that they actually cancel out. in total.

My idea is to maybe create imbalance in it by adding dc component to the current... or maybe add crossing capacitors...

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Re: Bifilar coil
« Reply #45 on: April 25, 2014, 20:31:15 pm »
The fact is the bifilar coils are a mystery sometimes, sometimes we are sure about what should it do but geon is doing correct he is testing it.


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New Bifilar coil tests
« Reply #46 on: August 04, 2015, 10:58:18 am »
lets talk about it...

but before try to zero up what were wrote up to here for now...

i developed a new winding technic i would like you guys to try and see what it does...

one is just like tesla bifilar spiral... two bifilar wires forming a mono layer spiral

(much like the one Geon was posting about... but with a core) i did with copper strip and paper between and over the strips...

second is again like tesla but the bifilar is wound forming a two layer but  the secret is every layer you must flip the bifilar wires alway on the same spot...

the third

it follow the spirit of the second but the coil is spread into a bobbin forming layers.. its important that the layers have positive wire of the bifilar right over the negative.. thats why a flip every end of layer will be needed... or reduce a turn every layer could work...  maybe its better in this case

the fourth uses wires.. . they are wound in same direction but alternating layers...

there is always insulation between layers and they must be uniform and consistent..

this is my effort to increase the capacitance of coils... this coils will have the same proprieties of tesla first bifilar spiral.. which was later on discover to be a very high voltage generator... he sure knew!

basically i hope you do some tests over this coils i'm proposing and if you do we can talk about what your results.. good luck


they should be driven with a pulse width variable frequency generator with a half bridge...

i don't think more than 100 turns...

i'm thinking to use speaker bifilar bound wire.. problem is the insulation must survive the voltages involved
« Last Edit: August 04, 2015, 19:47:42 pm by sebosfato »

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Re: Bifilar coil
« Reply #47 on: August 05, 2015, 04:35:22 am »
Some times I ask myself, what if i'm just loosing my time..   

Hope not!