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  #1  
Old 10-08-2010, 02:12 PM
wes wes is offline
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Default Bifilar Coil Inductance?

Hello, I have a quick question that maybe someone could answer here.

I know that if you have a Bifilar coil with the winding in a way so that the current goes in the opposite directions then your Inductance of that coil is close to zero (I know it will never reach 0, Impossible )

Now the part I am not sure about has to do with the bifilar coil when wound in series con-fig (I think it is series )

Here is a picture:
http://merlib.org/node/5516

it is the second one.

Would the this configuration have a lower inductance then a standard coil.

My reasoning for this is that since the coils are furthur apart, they would not be affected as much by the current flowing through the coils.

If you follow the flow of the current then you see that it travels withing the coil then exits back out and then goes back into the coil through the second winding?


So would the inductance be smaller or would it be the same as a standard coil or would it be bigger?
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Old 10-08-2010, 02:14 PM
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marshallf3 marshallf3 is offline
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Good question due to the mutual inductance.

You can compute the inductance of each coil given spacing, etc but two in perfect parallel?
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Old 10-08-2010, 06:29 PM
The Electrician The Electrician is online now
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When you have a bifilar pair like this, you can measure the inductance of one of the coils, ignoring the other; call that value of inductance L.

Now, if the two coils are connected in series aiding configuration, the inductance will be 4*L.

If they are connected the other way, series opposing, the inductance of the combination will be very small.
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  #4  
Old 10-08-2010, 07:40 PM
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Bill_Marsden Bill_Marsden is offline
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Which is why it is used to make resistors as opposed to conductors. All wires have some inductance, and by running next to each other, some capacitance. They also have resistance. The method of winding coils determines what characteristic is the predominant one used.

I'm willing to bet this is off a HHO site, because this quote...

Quote:
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!
is utter BS!. A bifilar coil with opposing windings stores no energy, the two opposing coils cancel the ability to store energy out. This is why it is predominately used for resistance. Do resistors store energy?

We have heard the same tired false arguments by all the HHO fans out there before Beenthere put his foot down.

http://www.allaboutcircuits.com/vol_1/chpt_8/12.html
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Last edited by Bill_Marsden; 10-08-2010 at 08:21 PM. Reason: Added qualification to Bifilar Coil
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Old 10-08-2010, 07:47 PM
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The two coils are not opposing, the current is still circulating clockwise, from A to B. Still I donīt see any point in this configuration apart from some different capacity.
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Old 10-08-2010, 07:48 PM
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Hello Bill,

You are probably right.
Take a look at post #106 of this thread from the energenicforum:
http://www.energeticforum.com/renewa...hematic-4.html

Lets see what beenthere thinks of it.

Bertus
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Old 10-08-2010, 08:17 PM
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Quote:
Originally Posted by kubeek View Post
The two coils are not opposing, the current is still circulating clockwise, from A to B. Still I donīt see any point in this configuration apart from some different capacity.
Look again at the second illustration, one coil is clockwise, the other counterclockwise, thereby canceling the inductance. I'm not sure what the capacitance would be. Overall I think it would have a very complex frequency response.

I thought beenthere would be interested in this thread (there is nothing wrong with it and it violates no rules), so I sent an email pointing it out.
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Old 10-08-2010, 08:25 PM
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Quote:
Originally Posted by wes View Post
Hello, I have a quick question that maybe someone could answer here.

I know that if you have a Bifilar coil with the winding in a way so that the current goes in the opposite directions then your Inductance of that coil is close to zero (I know it will never reach 0, Impossible )

Now the part I am not sure about has to do with the bifilar coil when wound in series con-fig (I think it is series )

Here is a picture:
http://merlib.org/node/5516

it is the second one.

Would the this configuration have a lower inductance then a standard coil.

My reasoning for this is that since the coils are furthur apart, they would not be affected as much by the current flowing through the coils.

If you follow the flow of the current then you see that it travels withing the coil then exits back out and then goes back into the coil through the second winding?


So would the inductance be smaller or would it be the same as a standard coil or would it be bigger?
You got it backwards, the first illustration is a true coil/capacitor circuit, the second has two coils in opposition to each other. I have seen it many times from HHO nuts. Tesla actually invented the first as a super simple way to build a resonant circuit. Components have gotten cheaper, so it is pretty well obsolete.
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  #9  
Old 10-08-2010, 09:51 PM
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Have another close look at the winding config guys, and the comment from Tesla - and think about what Tesla was up to!

His bifilar arrangement is configured to purposefully give the opposite 'low inductance' effect that you guys are thinking of.

Imagine applying a step voltage across one of the wires only, and what is generated across the other wire. Analogous to an automotive ignition coil.

Ciao, Tim
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  #10  
Old 10-08-2010, 10:23 PM
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kubeek kubeek is offline
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Quote:
Originally Posted by Bill_Marsden View Post
Look again at the second illustration, one coil is clockwise, the other counterclockwise
I think you should look again, both coils are clockwise.
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