From: Paul
Date: Sat, 17 Feb 2001 18:15:21 +0000
Subject: [TSSP] Reactive part of base input impedance
Hi All,
If the base input impedance is described, in the vicinity of
f1, by
Zin = Rin + jXin
where
Xin(w) = j(wLin - 1/wCin)
= jwLin( 1 - (w'/w)^2)
and w' is 2 * pi * f1, we might be forgiven for assuming that
the equivalent input reactances are given by
Lin = Les
Cin = Ces
However the model flatly insists that the correct values are
Lin = Lee
Cin = Les * Ces/Lee
so that
Zin(w) = Rin + j(wLee - Lee/wLesCes)
= Rin + jwLee( 1 - (w'/w)^2)
I've been trying to account algebraically for Lee appearing
in here - perhaps I'm missing some obvious fundamental relationship
between the energy storage ability of a resonator and the slope
of it's reactance near resonance. Any suggestions?
Perhaps a measurement would settle the matter? Terry, I think
you're the only one with a signal generator precise enough to
do this test. This would involve simultaneously probing
base volts and base current. Note the frequency at which the
two are exactly in phase, call that f1, and then find the
frequencies either side at which the phase difference is
+/- 45 degrees. From this, together with a Q measurement, we can
work out the effective value of Lin and see whether it equals
Les or Lee. Best done on the un-probed bare small coil, as the
difference between Lee and Les is the greatest.
I've been reconfiguring the model to look at output impedance,
with the eventual goal, in the next installment of 'theory notes',
of being able to write down a thorough lumped equivalent circuit
for the secondary.
Cheers,
--
Paul Nicholson,
Manchester, UK.
--
Maintainer Paul Nicholson, paul@abelian.demon.co.uk.