Re: Series resonance/Was: Waveguide TC

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

Original poster: "Malcolm Watts by way of Terry Fritz <twftesla-at-qwest-dot-net>" <m.j.watts-at-massey.ac.nz>

Hi Jolyon,

On 14 Dec 2002, at 9:51, Tesla list wrote:

 > Original poster: "Jolyon Vater Cox by way of Terry Fritz 
<twftesla-at-qwest-dot-net>" <jolyon-at-vatercox.freeserve.co.uk>
 >
 > Jim,
 >  >From what I understand an open-ended 1/4 wave transmission line is
 > series-resonant circuit; series resonant tuned circuit have 90 degree phase
 > shift between current at
 > the driven end (low impedance) and current at the terminal end (high
 > impedance).
 >
 > A lumped series-resonant circuit can be visualised as an inductor L and a
 > capacitor C
 > in series with a signal source or "generator". Surely there is a 90 degree
 > phase shift between current at the driven end and the current at the
 > "terminal" end i.e. current flowing "through" the capacitor?

How can there possibly be a phase difference if the current path is
common? There is certainly a phase difference in voltage developed
across each component.

 > There is a common belief (incorrect?) that the secondary of a TC is a
 > series-resonant
 > circuit - I might be wrong but would this not presume a 90 degree phase
 > shift between input and output-
 > whereas observations made on real TCs suggest little or no phase shift
 > between currents at the grounded and the terminal ends.
 > Is the "series-resonant secondary" like the quarterwave resonant theory
 > incorrect
 > -or is it possible to have a series-resonant tuned circuit with
 > little or NO phase shift between low-impedance input and high-impedance
 > output?
 > Or does the series-resonant voltage boosting effect involve not just the
 > secondary but
 > the primary as well -with the primary leakage inductance resonating with a
 > "transformed" value of the secondary capacitance via the magnetic coupling?

I think your problem is answered by considering what the current in
each component really is.

Regards,
malcolm