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Re: Method of measuring self C of secondary
Tesla List wrote:
> Original Poster: "Robert Jones" <alwynj48-at-earthlink-dot-net>
> The self C (true) or better the equation is required for simulation and
> maths models.
>
> The use of a voltage weighted C in a lumped resonance calculation or any
> calculation is totally new to me. As is the concept of a current weighted L.
You may be finding strange that the self-capacitance is not the
capacitance seen from the base of the coil at low frequency (C(0)), as
should happen if this model is valid:
o-----L-----+
|
base -> Cself
|
o-----------+
The inconsistency may be solved by adding another capacitor:
o-------+------L-----+
| |
base -> Cbase Cself
| |
o-------+------------+
Where Cbase = C(0)-Cself
In normal operation the base of the coil is grounded, and Cbase is
short-circuited. This is the condition assumed by Medhurst. It also
doesn't affect the frequency the impedance zeros (just one in this
model) seen from the base. It must be considered, however, in a
magnifier configuration, where the base of the coil is not grounded.
Note that Cbase causes an impedance pole (a maximum) at the frequency
where L resonates with the series combination of Cself and Cbase:
fpole=1/(2*pi*sqrt(L*Cbase*Cself/(Cbase+Cself))) Hz
This can be observed if you measure the impedance seen from the
base of the coil.
Antonio Carlos M. de Queiroz