Re: Magnifer vs. Tesla Coil

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

Original poster: "Antonio Carlos M. de Queiroz" <acmq-at-compuland-dot-com.br> 

Tesla list wrote:
 >
 > Original poster: Paul Nicholson <paul-at-abelian.demon.co.uk>

 > None of that makes much sense. Resonate at 1/8 wave? ..the 1/4 wave
 > frequency that the third coil resonates at?

I also don't see much sense in that description. To start, the
system is not working in sinusoidal steady state at one frequency.
These "wave modes" make some sense, however, if the voltage profile
along the secondary-tertiary system when the output voltage is
maximum is considered.

 > The combination of secondary and tertiary has two resonances
 > that we are interested in, you can call them 1/4 wave and 3/4 wave
 > if you want.  Adding in the primary splits the 1/4 wave resonance
 > into two modes, both 1/4 wave, but with opposite phase of primary
 > current.

If you consider the secondary-tertiary assembly as a single element,
there is some sense in saying that a magnifier operates in "3/4 wave"
mode. When the energy transfer is complete, the voltage at the top
of the third coil is maximum, and the voltage at the top of the
secondary coil is zero. Some voltage may remain around the center
of the secondary coil in a real system, but in a lumped model no
voltage remains anywhere in the secondary coil, with proper design.
And there is no need of a special relation between the inductances
of dimensions of the secondary and tertiary coils (many are possible).

 > As you increase the coupling on a TC, the level of the 3/4 wave
 > component increases - ie more and more energy goes into this (and
 > higher) modes.

A magnifier can really be adjusted to operate anywhere between the
"1/4 wave" (voltage rising continously along the secondary and
tertiary coils when the energy transfer is complete) and the "3/4
wave" mode, in the sense above. But it's not just the coupling
that causes the changes. The amount of capacitance across the
secondary coil is important too.

 > The aim of a magnifier is to split the resonant
 > inductance into two pieces such that the voltage peak of the 3/4
 > wave mode ends up sitting on the transmission line.

I would say the first zero (of voltage) of the 3/4 wave mode at the
transmission line.

 > This minimises
 > the voltage stresses along the coils.  The tuning is set so that
 > the 1/4 wave modes and the 3/4 wave mode combine to create a voltage
 > peak at the topload, simultaneous with the transmission line voltage
 > passing through zero, and the primary current and voltage passing
 > through zero.

Ok. A combination of the two modes. This may allow for the many
possibilities, each one with a different splitting of the system.
The primary voltage is zero too when the transfer is complete.

 > Antonio has provided the equivalent description to this tuning, in
 > terms of lumped values.

At http://www.coe.ufrj.br/~acmq/tesla/magnifier.html

 > So, the magnifier, if you want a definition, is a means to control
 > and exploit the 3/4 wave mode which would otherwise be a nuisance
 > if left to take care of itself - the nuisance being energy wasted
 > and racing arcs.

A nice interpretation.

Antonio Carlos M. de Queiroz