RE: [TCML] Bifilar coils

["Lau, Gary" <Gary.Lau@xxxxxx>]

The cited wiki page indicates that a flat bifilar-wound primary, with the two strands series-connected, was used by Nicola Tesla.  I am by no means an historical authority, but this seems like an unlikely and ill-advised way to build any kind of high voltage winding, as one typically wants to keep the two ends of a HV coil as far from one another as possible.  Primary coils for Tesla coils are never bifilar wound.

Some have suggested that a secondary winding may exhibit lower losses if two strands are wound in parallel, either side by side or one atop the other, to lower the effective resistance, but I don't think that a theoretical analysis or controlled comparison showed any improvement.

Your question about how to count the pair depends upon how the ends are connected.  In the previous paragraph, the two parallel strands are counted as a single, fat strand.  If the two strands are series-connected, then there would be twice as many effective turns and about 4X the inductance (but useless for a HV secondary).

Regards, Gary Lau
MA, USA



> -----Original Message-----
> From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On
> Behalf Of Peter Baitz
> Sent: Monday, November 16, 2009 7:04 PM
> To: tesla@xxxxxxxxxx
> Subject: [TCML] Bifilar coils
> 
> Hi all,
> 
> Questions about use of bifilar coils.
> 
> http://en.wikipedia.org/wiki/Bifilar_coil
> 
> I know this is used sometimes as a primary, but has anyone used it as a
> secondary?   Further, when making a bifilar, does one count the *pair* as the
> winding, ie. 700 turns is 700 pairs, or does one count 350 turns counting both
> additively 350+350=700  ?  I know this almost sounds trivial, but maybe it isn't?
> And does anyone know of a good bifilar calculator?
> 
> Thanks

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