Re: Tank Capacitance: what is the limit

Subject:        Re: Tank Capacitance: what is the limit
       Date:    Thu, 24 Apr 1997 07:59:28 +1200
       From:    "Malcolm Watts" <MALCOLM-at-directorate.wnp.ac.nz>
Organization:   Wellington Polytechnic, NZ
         To:    tesla-at-pupman-dot-com

Hi Brendan,

>         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?"

You can. However, the more capacitance you add, the less primary coil 
you will have. The Q of the primary will depend more and more heavily 
on the quality of the conductor used to make it. Also, for the same 
cap voltage your gap losses will increase as the primary currents 
become heavier (equivalent to losing Q). Also, the loading on the 
transformer becomes heavier. To charge a larger cap quickly needs 
less current limiting - something that is difficult to adjust with a 

My 2 cents,