Re: Mot DC Ps

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

Original poster: "by way of Terry Fritz <twftesla-at-uswest-dot-net>" <Mddeming-at-aol-dot-com>

In a message dated 2/17/01 11:42:58 PM Eastern Standard Time, 
tesla-at-pupman-dot-com writes: 


>
> 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 
>
>
> > > 
> > > 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 



If the frequency F of the oscillations is known for a given value of R, the 
effective parasitic L can be calculated from the equation 
F=sqrt(1/LC-(R/2L)^2)/2pi and then the critical value of R found from 
R=2*sqrt(L/C). In the absence of a way to measure F, yes, you can 
"guesstimate" L and try the resulting values of R until oscillation stops. 

Matt D.