At 10:17 2/18/97 -0500, you wrote:
>Hi folks,
>>From the 1995 Handbook, page 25.24:
>
>"The Half-Turn Problem
>
> When you wind toroids, remember that
>sticking the wire through the core counts
>as "one-half turn." Wrapping the wire
>around the core and passing it back
>through the core is one and a half turns.
>You can count the number of turns by
>counting the number of times the wire
>passes through the center of the coil. For
>an intergral number turns, the leads must
>leave the core on the same side. See Fig
>25.35A."
>
>Sounds to me that if you just staple the core
>to the board, you would have one-half turn.
>(3/4?)
>What say ye, Zack?
>
>72/73 Stew KE4YH
>Dunedin, Florida Spring Training home of the Toronto Blue Jays
>
>
Doesn't sound right to me. A toroid is just a core for a transformer or
inductor. One pass of the conductor through the 'window' of the toroid is
one turn. We do this all the time in the power industry with current
transformers.
I have 'proven' this to engineers several times that it doesn't make a lot
of difference if the conductor proceeds straight in one side of the toroid
and out the other with both sides of the conductor taut and straight on
either side for several feet or if it is wrapped around the outside of the
core making a complete loop.
If I need to cut the ratio between the primary winding (which goes through
the window) to the secondary (which is wound around the core, typically from
10 to 600 turns, then I loop the conductor through the window again, and
again, it doesn't matter where the wire goes after it leaves the window, as
lond as it doesn't pass through it. At least that's the way it works at 60
Hz with high-silicon iron ribbon-wound toroids with current magnitudes up to
several thousand amps going through the window and with 5 amps in the
secondary. Incidentally, these things I describe deal with voltages from
480 to several thousand. Above 15 KV we do things a bit differently.
I suppose that there might be some immeasurable difference here, but it
ratios out with the equipment we use in this industry. Perhaps at higher
frequencies there might be some sort of case to be made for flux leakage and
loss of capability for energy transfer, but one turn simply means that the
conductor in question goes through the window once.
Dale LeDoux
Sulphur, Louisiana
Bath Electrical Systems
Power Specialists -- 480 V to 230 KV
KD5QI -- QRP-L #602
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