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

Re: This phase shift stuff... - Plane Wave

Hi Antonio,

At 04:36 PM 2/21/99 -0800, you wrote:
>Tesla List wrote:
>
>> So it did what I thought it would.  From my other work, I suspected this
>> would be the case but I had never actually checked for the effect in this
>> detailed way.  The voltage along the secondary seems to rise and fall in
>> unison, just like a vibrating guitar string.  Even the harmonic seems to
>> act just like a vibrating string.  No phase shift effects.  Computer models
>> and calculations tell me there is a "little" phase shift (1.6 degrees) but
>> that is to small for me to measure.
>
>Why this phase shift? Losses? (see below...)

Using transmission line theory, there seems to be a small propagation
effect.  However, I would not be surprised if this little phase shift is
really not there.  Ambient electrical noise makes it hard to see very small
phase shifts to check this.  Perhaps I can find a way to measure it...
Recently, the more I look at the transmission line effects, the more they
seem to fall apart in the case of a Tesla coil...

> 
>> Antonio and I seem to have completely different results!  I did not see ANY
>> phase shift let alone a 90 degree shift.  Obviously, there is a little
>> correlation problem here!  :-) "Real science" may be needed to find what
>> the discrepancy is.  The effects are not subtle at all.  Anyone else who
>> would care to try, please do!  Antonio, if you have any ideas of what might
>> be wrong please let me know and we can work to resolve this.
>
>We were effectively thinking about different things. The -amplitude- of
>the
>voltage along a coil without top load at resonance follows (ideally) a
>90 degrees sinusoid, while the -amplitude- of the current follows a
>90 degrees cosinusoid.
>If you look at the phase relationship between the voltage at any point
>along the coil and the driving voltage, really there is -no- phase shift
>at resonance, and (in the lossless case) at any other frequency (there
>are 180 degrees phase changes at the voltage nodes at the high-order
>resonances). This happens in any lossless system, and as you could see,
>is what nature shows that really happens.
>The system behaves exactly as the rope analog.
>If there is a top load in the coil, the system continues to show no
>phase shift along the coil, but the amplitudes of voltage or current 
>along the coil, that continue to vary as a sinusoid and a cosinusoid, 
>don't reach anymore the 90 degrees variation.
>The difference between this model and the lumped LC model is that
>in the lumped model the voltage amplitude rises linearly along the 
>coil, and the current is constant along the coil.
>About what happens in a coil that is not small compared the the
>vawelength in air of the signal, I think that the behavior, at least
>in steady state, would be different only due to irradiation, that
>would be significant in this case.
>
>Antonio Carlos M. de Queiroz

I understand what you meant now.  I miss understood what you meant by the
90 degree thing...  We seem to be saying the same thing after all.  I
thought we were going to have some interesting controversy there for awhile
:-))

	Terry
References: