Re: Practical Magnifier Design ? ?

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: FutureT-at-aol-dot-com 

Chris,

The ratio of inductance between the secondary and resonator is an
important consideration for magnifier design.  If the ratio is low, a
higher voltage will be produced at the top of the secondary, and
excessive corona or driver flashovers are likely.  If the ratio is high
(small secondary inductance, large resonator inductance), the
coil will be better behaved, but will require a tighter driver coupling,
to obtain sufficient overall system coupling.  I've used ratios from
1:2 to 1:10 in my experimental magnifiers.  It can be seen from this
that a best compromise ratio must be used for best results.
Antonio's formulas may naturally lead to a particular ratio.

In my magnifier work, I never saw any efficiency improvement compared
to a normal 2-coil Tesla coil.  I did not do any tests over 5kW.  In one
experiment, I placed the resonator directly on top of the secondary,
thereby changing the coil to a 2-coil system, and the spark length
increased by 1".

To fully take advantage of Antonio's proposals, the gap must have
excellent quenching.  It's not clear if such quenching can be practically
achieved without excessive gap losses.  It's not clear to me if the
achieved spark length depends more on the initial resonator ring up
energy, or if it depends on the entire energy over the ring-down period.
If the initial energy is the key, then Antonio's method may provide more
of a benefit, even if the quenching is marginal.

Generally the driver is built rather large, to permit the use of thicker
wire to reduce losses, since the current is high in the driver.  The
resonator which sees a lower current, can tolerate the use of thinner
wire.  For example in one design, I used 140 turns of 18awg wire in the
secondary which was 11" diameter by 10" tall (the winding).  The
secondary was 10" diameter by 13" tall, and was wound with 24awg
wire.  This coil was run at 600 watts to 5000 watts or so.  I tried
various series quenching rotary gaps, but they gave no advantage over
a normal rotary.

The behaviour and performance of a typical magifier is very similar
to that of a normal 2-coil Tesla coil.  In some cases, the physical
layout of the magnifier design can be helpful for fitting the coil into
a particular building, etc, compared to a 2-coil classic system.

John


>But if anyone has any very practical information or a resource I could
>tap (without being too overwhelmed with "super hardcore" t! heory) I'd
>appreciate it. By practical information, I mean general rules, design
>equations, rules of thumb, construction tips, etc...)
>
>Thanks
>
>-Chris
>
>