Re: To cut or not to cut

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

Original poster: "Steve White by way of Terry Fritz <twftesla-at-qwest-dot-net>" <slwhite-at-zeus.ia-dot-net>

It seems to me that there is a single big advantage to having a variable
ballast. The first is that by turning down the current, I can reduce the
power input to the coil and thus reduce the streamer length for operation in
confined areas or for low power testing. Theoretically, the same could be do
be done by turning down the voltage control variac, but there is a practical
problem with this method: the spark gap. With reasonable spark gap spacing,
you are going to need thousands of volts to fire the gap. If you turn down
the voltage control variac too much, your gaps will not fire. Thus, by
having control over the maximum current, you can still fire your spark gaps
at 14000 volts or whatever and still operate at reduced power levels.

----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Wednesday, August 08, 2001 7:23 PM
Subject: Re: To cut or not to cut


> Original poster: "BunnyKiller by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<bigfoo39-at-telocity-dot-com>
>
> T> something I'm still trying to understand ( maybe the rest of the tesla
>
> > >  Gurus can help here) why do we
> > >  need to have a max voltage and controlled amperage? What does this
> produce?
> > >  What difference does 240V
> > >  in to a variac ( 280Vout) into an inductor that limits the current to
10 A
> > >  differ from 140V and 20A
> > >  supply??? )
> > >  the coil still sees 2800 watts approximatley..........
> > >
> > >  Scot D
> >
> > SNIPPERZZZ...
>
> >
> > John Freau
>
> Hi John...
>
> maybeee  I should rephrase the situation...
>
> what is the "added value" of having a variable current limiter  (
inductor) ?
>
> If you keep the voltage at lets say 240Vin to the piggie ( or whatever
> trannie) and
> control the current into the piggie and not vary the voltage, what I would
> see is
> the cap not getting fully charged and thus decreased streamer output.
> Wouldnt the
> same effect be produced by keeping the inductor at a constant and varying
the
> voltage via a variac?  Most variable "inductors" require moving a tapped
> line on
> the windings  ( ohh  thats right a 100 amp variac ;) ( almost linear
> control)  plus
> the range has to be very tightly controlled to keep from going into a
direct hi
> volume current flow (( the end of travel on the variac)) )  but
> seriously...  one
> has to unhook  a wire and reattach it to the next lug to change the
> inductance. OR
> we can unbolt the I section of the EI core and shim it up or down a bit to
> change
> the inductance once again...   seems like a lot of work .....  it would be
> nice to
> have a multipole switch attached to the different tap points and just
> simply flip
> the switch to the appropriate setting one wishes but...  not too often do
> we see a
> ceramic 300V insulated multipole switch rated for 75+ A.
>
> maybe Im biased I like my set inductor and Variac controller for voltage
:)  It
> allows me to increase streamer length ( up to full operating voltage) from
> 10" to
> 12 feet...
>
>
> Scot D
>
>
>
>
>