[Prev][Next][Index][Thread]

Re: This phase shift stuff...

Hi Antonio,

	A long thin secondary with no top load may be the best example to be
studied.  I worry about a probe disturbing the fields around the coil and
causing false measurements.  A physically large coil will be less
susceptible to this however.  Fiber optic probes made for the task (small)
may have very negligable efects.  A continuous sine wave may not be the
signal of choice.  Perhaps a pulse generator or arbitrary signal generator
would be the best thing to use even though that is on of the few toys I
still don't have ;-(
	
	I think the long thin secondary with no terminal is the best case where I
should be looking for phase shifting.

Thanks for the input!

	Terry



At 11:46 AM 2/17/99 -0800, you wrote:
>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
>
>
References: