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Re: Low Voltage Primary
Tesla List wrote:
>
> Original Poster: ross andrews <sflourine-at-home-dot-com>
>
> I am interested in using low voltages for the tank circut. If
one were
> to use a 240V tank circut, one would save the cost of transformers and
> caps, not to mention putting immense amounts of current through the
> primary coil. (all this stemmed from reading a paragraph about "it
> ain't the volts but the amps that matters").
Low-voltage primaries may be not a good idea:
As the energy E in a capacitor C at voltage V is E=0.5*C*Vmax^2,
each halving on the voltage results in quadruplication of the
capacitance for the same energy.
In a resonant tank (ignoring the secondary), the inductor L eventually
conducts current Imax sufficient to store all the energy that was in
the capacitor: E=0.5*L*Imax^2, or: Imax=sqrt(2*E/L)
As larger capacitance requires smaller inductance for the same
operating frequency, the current is larger if the capacitance
is larger, for the same energy E and frequency F. Combine the
last expression with F=1/(2*pi*sqrt(L*C)) and you have:
Imax=2*pi*F*sqrt(2*E*C)
The maximum inductor current is proportional to the square root
of the capacitance.
Consider also that all this current must pass through your large
capacitor, without significant inductive or resistive effects...
Antonio Carlos M. de Queiroz