And further: No more than 3 or 4 non-overlapping turns through the
toroidal core.
Dave - WØLEV
On Thu, Oct 19, 2023 at 6:25 PM Jim Brown <jim@audiosystemsgroup.com> wrote:
> On 10/19/2023 5:46 AM, nlsa@nlsa.com wrote:
> > When applying a common-mode filter (such as toroids) to a North American
> > 220VAC line, only the two "hot" conductors should be included, correct?
> Not
> > the neutral.
>
> If it is ONLY 240V, load current is on the two "hot" conductors, but
> noise is often present on the ground, so all three should be wound
> through the toroid core. Fair-Rite #31 is the weapon of choice for HF
> and VHF through 6M.
>
> If that 240 branch circuit feeds both 240V and 120V outlets, all four
> conductors should go through the core.
>
> The best ways to wind these chokes are 1) use a suitable length of NM
> (Romex) or 2) use three or four THHN solid conductors taped together to
> go through the core, splicing to whatever conductors are used for the
> circuit. In general, the choke should be as close as possible to the
> noise source.
>
> In general, twisted pair/triplet/quad resists radiation of noise, and
> should be used when practical. I build twisted/triplet by cutting equal
> lengths of three colors of THHN stranded, putting one end in a bench
> vise, the other in a drill motor, pulling them taught, and running the
> drill motor slowly to produce the twist. Let the twisted cable sit at
> least overnight to develop memory. When released, it will untwist a bit,
> and twist ratio will not be equal from one end to the other, but that's OK.
>
> 73, Jim K9YC
>
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>
--
*Dave - WØLEV*
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