Our coil has a bifilar secondary, but one copper wire is interwound with a
nylon monofilament of the same diameter (#26 and 0.015"). This is to reduce
the interturn capacitance and to provide more interturn insulation. The
total resistance of the secondary is 213 ohms. Switching the nylon for
copper has little effect on the Q, since it reduces the output voltage less
than 0.5%, according to my MicroCap program. When we wound it, we knew we
were in for trouble, so we allocated a whole day for the process. It
actually took 20 minutes, since we had no problems.
---Carl
-----Original Message-----
From: David Thomson
Sent: Thursday, March 20, 2014 9:53 PM
To: Tesla Coil Mailing List
Subject: Re: [TCML] Bifilar Coils
On Thu, Mar 20, 2014 at 9:51 AM, dave pierson <dave_p@xxxxxxxxxxx> wrote:
> Bifilar coils effectively increase the wire diameter by two. The
> difference is a higher current, lower potential output at the
> top load.
I can't think why the potential would drop?
Think (approximation only) of two secondaries
in parallel:
But there are not two secondaries. There is only one with a thicker wire
and half the turns.
> Now that I think about it, It also seems to add
> an extra dimension to the resonance in the secondary.
> Instead of having a single conductor in
> resonance, there are now two conductors in resonance.
Should be the same resonance?
It might be, but if the two conductors are electrically isolated and there
is a different capacitance in one leg than in the other, then the LC
calculation would have to change. The inductances and potentials will be
the same, but the capacitances would be different.
> I haven't tried it on my bifilar and trifilar coils,
> but it seems that putting a capacitor in line with one
> of the wires could have a unique effect. For example,
> causing the second wire to be 90 degrees or 180
> degrees out of phase with the first would
for the 180 cause: the output to go to zero as
the two secondaries cancel?
Yes, you are probably right about the 180 degree case. In fact, the phase
difference would probably need to be fairly small to still have a spark.
Dave
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