Re: Tank Capacitance: what is the limit

Subject:      Re: Tank Capacitance: what is the limit
      Date:   Wed, 23 Apr 1997 19:34:30 -0800
      From:   Greg Leyh <lod-at-pacbell-dot-net>
        To:   Tesla List <tesla-at-pupman-dot-com>

Brendan Haley wrote:

> "Why can't you increase the capacitance indefinitely,  and
> retune your primary appropriately,  in order to achieve more 
> current in the tank circuit?"

There are two limiting factors:

1)  The max. AC mains power available -- In order for the coil
to perform well, it must fire at least 200 times per second.  
Given that, the total power draw will be 200 PPS times the energy 
stored in the primary cap, which is 0.5 x C x Vsquared.

2) The min req'd Q factor for the primary ckt -- the unloaded Q of 
the pri ckt should 10 or greater, otherwise the rotary gap starts
to dissapate too much power.  The Q of the pri is approximately
SQRT(L/Cpri) divided by Rgap.  Since Rgap is more or less fixed,
it can be seen that an arbitrarily large pri cap will result in
in a low Q, with most of the input power being dissapated in the gap.