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Re: Magic K values
Hi Skip,
Should have replied to this one a few days ago......
> In December Bert was kind enough to post a list of magic K values and
> their derivation.
>
> I have a question. These values are derived from parameters which are
> measured when the TC is not energized. We all know that for various
> reasons the resonant frequency of the secondary goes down while
> energized due to the fact of the ion cloud and possible other factors.
> With this in mind how can the K values be accurate? Furthermore, it
> seems to me that
> different toroidal loads on different secondaries would give different
> amounts of terminal capacitance so that one could not extrapolate values
> obtained from ststic measurements. If the numbers don't hold for
> different configurations, what good are they? I would appreciate any
> comments that the members might contribute.
k is set by the flux linkages between two inductors. The standard
formula is:
k = M/SQRT(L1.L2) where M is the mutual inductance.
It can only be changed by altering the inductance of either coil or
if the relative coil positions are changed to alter the flux linkages.
What does vary is the value of kc since it is Q dependent:
kc = 1/SQRT(Q1.Q2)
Equating the two shows the aggregate value of Q at which coupling
becomes critical.
e.g. suppose k = 0.1 and Q1 is 10. A system so set is overcoupled
for any value of Q2 above 10.
Malcolm