RE: Meter Shunts ?? - new current

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Steve Conner" <steve.conner@xxxxxxxxxxx>

>Does anyone know the exact equation to find the new current from a
>capacitor? This equation in particular I can not seem to find anywhere

I'm not surprised. I'm an EE and I've never heard the phrase "new current"
used in this kind of context before.


I can only assume that you got it from this page

http://users.tm.net/lapointe/HowItWorks.htm

which was one of the first hits that Google produced for "capacitor new
current"


In this case, the answer is related to the "surge impedance" of the tank
circuit. If you charge a capacitor C to a voltage V, then connect it to an
inductor L, the peak value of the oscillating current I will be:

I=V/Z where Z=sqrt(L/C)


This applies to a single lossless LC resonator. If you want an exact answer
for a Tesla coil with losses and two coupled circuits, you have to get back
to basics and solve the differential equations describing the system. We
normally use a simulator like Orcad PSpice for this rather than doing it by
hand.

But in practice, the surge impedance formula gives a reasonable answer for
the peak primary current in the first half cycle, so it is good enough for
estimating peak current stresses on your capacitors and such like.


Steve C.