Re: Capacitor value not clear yet.

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: Terry Fritz <teslalist-at-twfpowerelectronics-dot-com>

Hi Gerry,

Yep!! ;-))

I can never remember the simple one of the top of my head.  But I always 
seem to remember how to do it the loooong way.  Indeed, most of my math 
with cancel out leaving the nice equation you give.  But I think one has to 
go through the long math just once in their lives ;-))

Actually, the "R" does affect frequency and such too, but in our circuits, 
we neglect it since the effect is trivial.

Cheers,

         Terry

At 09:51 PM 1/12/2004, you wrote:

>Terry,
>
>Ah, math is beautiful isn't it?
>
>Max I = V / sqrt (L/C) using your values = 282.8 amps
>
>Gerry R
>
>
> > Original poster: Terry Fritz <teslalist-at-twfpowerelectronics-dot-com>
> >
> > Hi Luke,
> >
> > The primary current is a function of the primary resistance, frequency,
>and
> > inductance.
> >
> > If the resistance is 0.1 ohms and the inductance is say 100uH and we have
>a
> > 20000 Volt primary cap at 20nF, we can find the peak current.
> >
> > The inductance will have a value Zl which is generally referred to as
> > complex impedance or reactance.  This acts much like resistance.
> >
> > Zl = 2 x pi x Fo x L
> >
> > Fo = 1 / (2 x pi x SQRT(L x C)) = 1 / (2 x pi x SQRT(100e-6 x 20e-9) =
>112540Hz
> >
> > Thus  Zl = 2 x pi x 112450 x 100e-6 = 70.7 ohms
> >
> > The total impedance is Z = SQRT(R^2 + Zl^2) = SQRT(0.1^2 + 70.7^2) = 70.7
> > ohms.  The 0.1 ohms of resistance is very small compared to the 70.7 ohms
> > so it really does not make any difference here (but it does matter when it
> > comes to coil losses!).
> >
> > The peak current is the voltage divided by the impedance:
> >
> > 20000 / 70.7 = 282.88 amps.
> >
> > Cheers,
> >
> >          Terry