Re: How to calculate power in tank circuit?

Hi Doug,

	Tank circuit does not "store" power.  It stores energy.  Power is the RATE
at which that energy is consumed.  The system resonant frequency has
nothing to do with it.

The energy in a capacitor is equal to E = 1/2 x C x V^2    Joules
The energy in an inductor is equal to E = 1/2 x L x I^2    Joules

The power (in Watts) is equal to the number of Joules the system consumes
in 1 second.  Watts = Joules / Second.

To know how much power is being used, you need to know how many times per
second the spark gap fires (BPS).

If you know the following, you can find the power the primary circuit is
sending to the system.

Capacitance of primary capacitor  Cp
Voltage the capacitor is carged to when the gap fires  Vf
How many times per second the gap fires  BPS

Then the power is  W = 1/2 x Cp x Vf^2 x BPS     Watts

So if you have a 10nF cap,  20000 Volt gap, and 120 BPS rate (very typical
15kV  60mA neon system values) you get the following:

W = 1/2 x (10 x 10^-9) x (20000^2) x 120 = 240 Watts

But if you feel "lucky" you might increase the gap to 30000 volts.

W = 1/2 x (10 x 10^-9) x (30000^2) x 120 = 540 Watts!

Twice the power!  ...Until the neon blows :-))

I have been playing with a 15kV neon system that uses big caps instead of
high voltage.  It has the following primary power.

W = 1/2 x (27 x 10^-9 x (21000) x 120 = 714 Watts.

Not sure I would recomend it to anyone yet until more testing is done....

Hopefully you see the idea.  How much of that power actually makes it into
the streamer is another much longer story.....



At 05:17 PM 1/2/99 -0500, you wrote:
>Just want to see if I have this figured out right. Is the power stored
>in a tank circuit, assuming ideal components, the maximum energy stored
>in the cap times the resonant frequency?
>So, if maximum voltage = V, capacitance = C, frequency = F, and power =
>           --Mr. Postman (Doug Brunner)
>                <dabrunner-at-earthlink-dot-net>