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abudabit (Automotive) (OP)
21 Sep 09 17:17
I've never used Bifilar Winding, and had a question regarding some conflicting information.  This is for parallel bifilar winding where the current flows in the same direction in both wires.  

I've seen it said that bifilar winding 'multiplies' the inductive field.  But that doesn't seem to make sense to me, since parallel inductors reduce total inductance.

Let's say for a particular core I need 20 windings of a single wire to get X microfarads.   How many windings of each wire would be needed for a bifilar on that same core to get X microfards?

Thank you lots, my litz choices are limited so I need to do bifilar to meet my ampacity needs.
jimbofitz (Electrical)
21 Sep 09 17:29
A bifilar winding acts as a single conductor with increased cross sectional area.  It doesn't affect the magnetic field in a special way.  If you need bifilar windings of Litz wire in parallel to meet both AC and DC resistance, you can treat it as a single conductor.  The same applies for trifilar and any number of wires in hand.  

Proximity affect and fringing flux from other windings and the core gap(s) would be the inductive concerns IMO.

 
Skogsgurra (Electrical)
21 Sep 09 18:02
How do you mean? Getting microfarads out of a winding? Are you sure you don't mean microhenries?

Gunnar Englund
www.gke.org
--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

abudabit (Automotive) (OP)
21 Sep 09 18:09
Thanks Jimbo, that makes more sense.

Skogsgurra, good eye.  Yes, I meant henries.
Comcokid (Electrical)
21 Sep 09 18:49
Sometimes bifilar wire, or multi-stranded wire, where the wires have different enamel colors so that several independent windings can be wound together.

In other cases, multiple parallel wires, or litz wire will be used to wind.

First of all, using many parallel wires increases the cross-sectional area allowing for more current as jimbofitz pointed out. And, its sure is a lot easier to wind several 18 AWG wires rather than a single 12 AWG as well.

Secondly, if the transformer or coil is being used at high frequencies, then skin effect may be important. That is why sometimes you will see woven wire (litz wire) consisting of a large number of very small gauge wires being used together for a high current winding.
 

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