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Re: This phase shift stuff...
Tesla List wrote:
> So what kind of REAL Tesla coil system can I put together that
will show
> all that phase shift, 1/4 wave, and transmission line effect stuff?
> Perhaps, it is a forgone conclusion that the secondary voltages and
> currents are pretty much in phase within a Tesla coil (there really is a
> "little" shifting). However, if anyone has a major exception, I have the
> resources ready to pour into reproducing and studying this exception. It
> is time to put this matter to rest once and for all...
Make a coil -without- top load. It is obvious then that when voltage at
the top is maximum the current is zero. Adding more capacitance to the
top changes this situation continuously, eventually ending with an
essentially lumped model.
You can measure the voltages along the coil easily if you operate it
at low power and use a small capacitive probe actually touching the
coil.
I made these measurements some time ago, operating a coil at low
power, driving the primary (gap short-circuited) with a high-impedance
current source (a few mA) in parallel with the Lpri-Cpri tank.
With a low-frequency square current wave applied, it is easy to see
much of what is happening by observing the beat voltage waveforms
that appears over the primary, at low impedance.
It is easy to "map" the electric field along the secondary by just
sliding a finger along it, changing the distance to keep constant
distortion in the primary beat waveform. The primary can also be tuned
to other resonance modes of the secondary (ideally 3x, 5x, 7x, ...
the main resonance frequency without top load, but practically
somewhat below these values due to parasitic capacitances), and
the voltage nodes at the secondary are easy to observe by the
same "mapping" method, up to the 10th resonance mode in my setup.
Antonio Carlos M. de Queiroz