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Re: bi-polar (center-fed) TC
One problem that most experimenters building bi-polar center-fed
Tesla coils fail to take into consideration is the difficulty of
adjusting the coupling. If you simply slide the primary more
towards one side, you increase the coupling on one side and
decrease it on the other side.
If the experimenter fails to ground the secondary at its center,
then approaching either of the ends will cause the voltage on the
other end to change drastically. Quite often the circuit will
respond by causing sparks to fly between the primary and the
secondary at or near the center.
For these reasons it is generally better to make a bi-polar
Tesla coil that uses two distinct secondaries having the bases
both tied to a really good common RF ground. Such a bipolar
Tesla coil will have separate primaries for each secondary.
The coupling of each can be independently adjusted.
The primaries
have to be properly phased so that the tops of the two secondaries
are out of phase. You can wind the secondaries in the same direction
and the primaries in the same direction, and achieve proper
phasing by just phasing the *connection* to the primary. There
is NO need to wind any of the coils differently (although that is
just as valid a method to achieve proper phasing).
Hope this helps.
Fr. Tom McGahee