# Tank Capacitance: what is the limit

```Subject:  Tank Capacitance: what is the limit
Date:   Mon, 21 Apr 1997 11:13:22 -0400
From:   Brendan Haley <bhaley-at-shore-dot-net>
To:   "'Tesla'" <tesla-at-poodle.pupman-dot-com>

Hello all-

I'm sure this question has a simple answer,  and I'm a bit tired
of

My intuition is that,  given a transformer with certain
properties (output
voltage and current),  there is an ideal tank capacitance at which the
circuit
(transformer -> cap. -> inductor(primary)) will run optimally.  My
friend however
asks me:  "Why can't you increase the capacitance indefinitely,  and
retune
your primary appropriately,  in order to achieve more current in the
tank
circuit?"

Again,  my intuition tells me that the answer is that you can't
just
arbitrarily increase your capacitance to gain current,  but I'm not sure
exactly
why.  I have a feeling it has to do with the interaction between the
capacitor
and the xfmr,  perhaps related to the impedence of the capacitor, and
the ideal
load on the xfmr.  Or perhaps is it a frequency related thing having to
do with
the LC circuit formed by the seconday of the xfmr and the capacitor.

Can anyone shed light on this,  and perhaps bolster or destroy
my faith
in my own intuition.

Also,  could anyone send me the formulas for determining  the
appropriate capacitance for a transformer, and the appropriate
inductance for
the primary,  given a desired freq.,  as this may help me figure this
out
as well.  I used to have these,  and they are probably in a book
somewhere,
on my bookshelf,  but I am having trouble finding them.

Thanks Again,

Brendan

```