Bifilar Coils

[Murlin]

I was doing some reading and came across this coil design.

If I an reading this right, the inductance of the coil would be Zero.

Take 3 to 6 wires and crimp the ends together and bend them in the middle, then wrap those 6 to 12 wires around the coil jig.   It would be a bifilar coil and you would just have both leads comming from the top of the coil.

Could this coil be any good for a generator, or is it used in transformers only?

Murlin

[Flux]

Description is too vague to mean anything, it depends what the jig is.

At first sight it is a description of how to make non inductive resistors but equally well it could be formed into an inductive coil.

Non inductive windings are totally useless except for non inductive resistors, you can not make alternators motors transformers or anything else with non inductive coils.

Flux

[Murlin]

From what I understood, it was a coil kinda like this:

Except for more turns. This drawing only has one turn.

Just curious what something like that would be used for...

Murlin

[Flux]

Non inductive resistors or possibly resistance temperature detectors for use near magnetic fields are the only uses I can think of.

Flux

[Murlin]

Thanks Flux,  no need to do any with that type of coil then.

I came across some magnet wire, so I was going to do some coil experiments.

On the topic of coil geometry:

I was going to coarsly braid 3 wires together.  Then take 2 of those braids and make a test coil.

Was thinking of 23 turns of 6 in hand, 3/4 x 1 1/2 x 3 mags.

Since there will be some air gaps, I will not be able to keep the exact same size as DanB's coils on his 20 footer.

I am either going to have to make the center hole of the coils smaller or the ends of the hole longer.

Any suggestions could save me a bunch of time if anyone has any comments.

I know alot of you guys have done alot of experimenting with coils and this is my first attempt at something I know very little about.  

Thanks so much for your time.

Murlin

[willib]

there are some advantages to having both ends 'end ' at the outside of the coil.

one is your coils end up thinner.

another is there is no chance of the middle wire shorting against the rest of the coil.

[TomW]

willi;

Well, that coil shown in the graphic would have a net induced voltage of "0" since it is essentially one wrap in each direction. Or looks that way to me. One "half" would be positive and the other would be negative. Seems like that would cause cancellation measured at the leads, but I have not tested it at all. That may be a bit of an issue creating a useful coil to create electric current.

Just my opinion and could be wrong.

Cheers.

TomW

[willib]

Tom you are correct , i did not see the graphic when i made the comment.

[stop4stuff]

In an alternator, EMF is induced according to Fleming's Left Hand Rule.

Previous comments stating there'd be zero output are spot on.

In the diagram below, the red & blue disks represent north & south poles

of magnets and the small arrows represent the direction of the induced EMF,

as one can see, the direction of the EMF clashes...

heat woud be created, but no electrical output.

paul

[Flux]

You are right about everything except the heat. No emf, no current, no heat.

Flux

[stop4stuff]

really?

in one part of the coil, emf is induced in one direction, the other part, emf in the other direction... i respect your comments Flux, but are you saying that when the emf cancels the energy just disapears?

[Murlin]

Ya... non inductive resistors....Could these be used for increasing the efficiency in your stator?

Possibly absorbing some of the heat without sucking down any voltage?

Until yesterday I never heard of a bifilar coil, so I am probably thinking about stuff I have no business thinking about, lol....

[Flux]

There is no energy expended in inducing an emf. If the emfs cancel there can be no current. Without current flow no energy is used.

I have seen this argument used about cancellation in coils, it doesn't cause heat.

Flux

[TomW]

stop;

Well, i guess the fact that there is no "complete" circuit there can be no current flow. Same as a couple "D" cells placed + to + no complete circuit no current flow.

Then, again, I am not really sure how it would work in that setup? Even if the leads were shorted there probably is no current flow. Interest skull exercise that could probably lead to an entire Senior Paper if you tracked it down as to whats going on there.

Interesting stuff, regardless.

Cheers.

TomW

[TomW]

flux;

Good explanation. Big difference in inducing emf and using it.

Thanks.

Cheers.

TomW

[Murlin]

Ok well there is one thing I do not understand.

If the electrons in the copper wire are excited with the collision of magnetic flux, then wouldn't the electrons still flow to the end of the wire, following the path of least resistance?

It is my understanding that the copper atoms then act like little magnets themselves all trying to line up .

When an electron reached the center of the wire and started traveling back the other direction wouldn't it just reverse polarity and keep right on going to the end of the wire and still have some sort of energy?

Hrm very puzzling indeed...

[tecker]

You can wind bifillar ( Two in hand three in hand etc.)to increase amperage with a doable bending radius. The connection forces a cancellation .On the other hand this method makes an excellent directional magnet common to things like vertical Yoke on a cathode ray tube.

[Murlin]

Ahh ok..CRT's use them...

I will accept the principal of the voltage cancelling for now without understanding the particulars.  You could use this.

Since one uses Bifilar Coils for high current switching.  If you ran a bifilar winding with your primary coils somehow, could you switch your coils on and off by energizing the bifilar?  You wouldnt need fancy electronics to control switching, just current.

You could do all kinds of stuff with this I am thinking.  Maybe switching coils on and off as they go past the magnets could accelerate electrons faster than would be normally be done and create more power...don't mind me, just the ramblings of a mad man....

Or maybe you could switch back and forth between 2 sets of windings without the sudden shock that throwing a switch would cause?

I am thinkin' a two'fer....again....

De ja voooo....

Murlin

[tecker]

They're fun  .Little wire strethers they are . The repulsion really jumps .  

[Gordy]

Murlin,

I think I have an easy way to demonstrate what other are saying. Take a garden hose filled with water and make your coil. Now put 2 equal pumps on it to simulate the magnetic force one pump pumping to one end of the hose, the other pump pumping to the other end.   Turn both pumps on at the same time. What's going to happen ? Nothing both pumps are fighting each other.

Gordy

[Capt Slog]

I don't think braiding is a good idea, it uses far too much space.

Take a look at this....

http://www.fieldlines.com/story/2006/10/21/61110/798

It's a thing of beauty and genius!

[Murlin]

Yes, I have been watching Sammopowers posts with great interest. I love his coil winder.

There has been talk about that type of coil design being more prone to the skin afffect.

I await progress reports.

In the mean time, since I can't see that any experiments have been done with litz wire coils, I will gamble and try some.

I just don't know if I should go with a smaller hole or a longer coil to get the same amount of copper to fit in a given space.

Murlin...