Re: Mot DC Ps

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

Original poster: "Luc by way of Terry Fritz <twftesla-at-uswest-dot-net>" <ludev-at-videotron.ca>

Tx Matt

You lost me after the first paragraph but R=2*sqrt(L/C) is simple if I
don't have
any real inductance except for parasitic could I use something like 10ˆ-6 H for
value of L in the equation.

Luc Benard

Tesla list wrote:

> Original poster: "by way of Terry Fritz <twftesla-at-uswest-dot-net>"
<Mddeming-at-aol-dot-com>
>
> In a message dated 2/17/01 4:15:15 PM Eastern Standard Time, tesla-at-pupman-dot-com
> writes:
>
> >
> > I have a question too when you discharge a cap though a resistance for a
> > certain value of R you have an oscillating circuit (because of parasitic
> > inductance ), if you increase the value of R to a certain point the cap
> > will just discharge whit out oscillation how do you calculate this
> > value.
> >
> > Tx
> > Luc Benard
>
> Hi Luc
>         The critical point is at R=2*sqrt(L/C). If R is greater than this
> value, no oscillation takes place. The frequency equation f=1/((2pi*sqrt(LC)
> is actually a simplifications of:
> F=sqrt(1/LC-(R/2L)^2)/2pi
>
> This follows from the circuit current as a function of time being:
>
>         I(t)=Vo/Lw * exp(-at) * Sin(wt), where a=R/2L and
> w=sqrt((1/LC)-(R/2L)^2) and Vo is the initial voltage on the capacitor.
>
> If you need a complete derivation of this, write me on or off list.
>
> Matt D.