Re: Math help...

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

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

Hi Bert

Tx that's exactly what I want, I did not know that the same
amount of power is dissipated in the resistor than in the cap,
what a short cut for calculation! 

I use the water resistor not for efficiency but it's practical
for small experimental coil were I only need a small part of the
power available but need stability from the PS.

An update on the PS circuit: I'll have the possibility to
interchange the microwave caps filter for a bigger electrolytic caps.

Tx again Bert,
cheers,

Luc Benard   

Tesla list wrote:
> 
> Original poster: "Bert Hickman by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <bert.hickman-at-aquila-dot-net>
> 
> Luc,
> 
> It can be shown that if a capacitor is charged through a resistor, and if
> the charge time is sufficient to virtually fully charge the cap (Tcharge >
> 3RC), then the series resistor will dissipate the SAME amount of energy as
> the energy that ends up being stored in the capacitor. Knowing this
> simplifies the problem a bit.
> 
> If the Energy/bang = 0.5*C*(V^2) Joules and the break rate = X
> bangs/second, then, the power transferred to the TC primary circuit will be
> 0.5*X*C*V^2 Watts, and the power dissipated by the series water resistors
> will be the SAME (for 50% efficiency by the charging system):
> 
>    Presistors = 0.5*X*C*(V^2) Watts
> 
> Because of the significant inefficiency (only 50% max), pure RC charging
> systems are seldom used for higher power pulse work, and reactive (LC)
> charging systems are preferred instead. Note that the above analysis
> assumes that the primary cap is fully recharged between breaks irrespective
> of the break rate. This means that the time between breaks must be at least
> 3*R*C:
> 
>   1/X = 3*R*C
> 
> For 400k ohm water resistors, and 120 BPS, this means that the maximum tank
> circuit capacitance can only be about 0.007 uF. If you want to use larger
> tank caps, you'll need to reduce the value of the charging resistors.
> 
> -- Bert --
> --
> Bert Hickman
> Stoneridge Engineering
> Email:    bert.hickman-at-aquila-dot-net
> Web Site: http://www.teslamania-dot-com
> 
> Tesla list wrote:
> >
> > Original poster: "Luc by way of Terry Fritz <twftesla-at-qwest-dot-net>"
> <ludev-at-videotron.ca>
> >
> > Hi guy
> >
> > I presently build a DC power supply for coil. I want to be able
> > to use it for big coil but mostly for small one, you could see
> > the circuit at:
> > http://pages.infinit-dot-net/luc2/ps_mot_3.gif
> >
> > Some of you will tell me to use a variarc for power control; I
> > have some but I choose to use variable water resistor for many reason.
> >
> > Any way I need to have an equation to know at different value of
> > power how much power will be dissipated in the variable resistor
> > and the primary circuit ( power in the V. resistance + power in
> > the primary circuit ), I already know some equation : capacitive
> > energy J=C*V^2/2, ohm law V=I*R, P=V*I, P-V^2/R, transient
> > V-(Vf-Vi)*e^-T/RC, but can't merge them in a big equation...:-((.
> >
> > What I want to have is an equation where variable are PS voltage,
> > cap value, break rate, value of my variable resistor, one of the
> > unknown will be the power dissipated in the variable resistance
> > when the SG conducted, it could be estimated like a short of the
> > PS across the V. resistance for the time the gap conduct, but an
> > approximation will do the job. The output of the equation will be
> > the power use in primary circuit and power dissipated in the
> > variable resistor.
> >
> > If one of you could help me with that or make a small excel file
> > I'll be eternally thankful ;-) .
> >
> > Cheers,
> >
> > Luc Benard
> >
> > *This post and an other one was send friday at 1:00 PM but both
> > never make it to the list...???