Re: MMC cap bank

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

Original poster: "Terry Fritz" <teslalist-at-qwest-dot-net>

Hi Jimmy,

At 01:12 PM 7/4/2003 -0700, you wrote:
>Hi Terry,
>
>I understand the I^2R thing, but isn't the RMS current
>only square root of 10 times as much? After you square
>and average it, it would be 10 times, but you still
>have to take the square root, right?

Nope.  RMS is just the "equivalent" AC current to a fixed DC current.  If I 
run 10X the BPS rate, I draw 10X the current and get 100X the heat loss 
across a resistor.


>If it really is 500 watts lost with 1000 BPS, then the
>amount of energy lost per pulse is 0.5 joules. If you
>lose 5 watts at 100 BPS, then the energy lost per
>pulse is 0.05 joules. What would cause the increase in
>loss per break?

It's not linear.  "I^2"  The graph is a steep ski slope.

>We are talking about the same energy
>per pulse right?

Yes.  Power = current squared times resistance.   Double the current, four 
times the power.  Triple the current, nine times the power...



>--- Tesla list <tesla-at-pupman-dot-com> wrote:
> > Original poster: "Terry Fritz" <teslalist-at-qwest-dot-net>
> >
> > Hi Jimmy,
> >
> > Suppose we have 10 amps RMS at 100 BPS and our caps
> > are 0.05 ohm of
> > internal resistance (typecal for a 15/60).  From
> > P=I^2R the power lost as
> > heat in the caps is 5 watts.  Now lets hook it to a
> > pole transformer and
> > run it at 1000 BPS for 100 amps RMS:
>Use my signature  Allow HTML tags [Preview]
>
> >
> > P = I^2 x R  == 100^2 x 0.05 = 500 watts.
> >
> >   The array can run all day at 5 watts.  But 500
> > watts it will die
> > fast!!  Probably like 15 seconds.
> >
> > Cheers,
> >
> >          Terry
> >
> > At 09:07 PM 7/3/2003 -0700, you wrote:
> >
> > > > Second, keep the BPS rate LOW.  Capacitor
> > current is
> > > > directionally
> > > > proportional to BPS.  3000 BPS has 10X the
> > current
> > > > of 300 BPS and 100X the
> > > > cap heating!!!
> > >
> > >Hi Terry,
> > >
> > >I "think" the heating should only be 10x as much.
> > If
> > >it were 100x then each burst would have to waste
> > 10x
> > >the power, and I don't see how that is possible.
> > The
> > >average current will be 10x as much, but the RMS
> > will
> > >only be SQRT10x as much because the duty cycle is
> > >greater. Check me on this because it's getting late
> > >for me ;-)).
> > >
> > >=====
> > >Jimmy
> >
> >
>
>
>
>=====
>Jimmy