[Prev][Next][Index][Thread]

Re: As a thought experiment...



Hi Yuri,

>Original Poster: "Yuri Markov" <wmondale-at-hotmail-dot-com>
>As a thought expiriment, how would a coil function if its ordinary spark gap
>were replaced with a jacob's latter-type configuration? Has anyone tried
>this? I intend to as soon as I get my coil to work with an ordinary gap. If
>you have, I'd like to know your results. The combination would make one heck
>of a light show!

Lemme give this a stab:

First of all, letīs try to understand what a Jaccobīs Ladder is. It is
simply two pieces of wire shaped into a V. Why is this done? Well,
JL are (were) used as lightning surge arrestors. Imagine a HV line
being hit by lightning. The voltage rise is dramatical. The JL starts
to arc and clamps the voltage to a safe limit. Now comes the neat
part (making it useless for TC work): If the JL gap was simply two
pieces of parallel running wire, the arc would start, but continue
arcing, even after the voltage surge was over. To shut the arc off,
you would need to turn off the power to the power lines. Not very
effective. The V shape helps out here. The voltage rise causes
the spark to jump near the base of the V. The arc creates heat
and this causes the spark to rise. The longer the spark gets, the
higher itīs resistance becomes (and this R problem is why it
would be an extremely lousy spark gap in TC usage) . Eventually,
the arc rises so high, that it canīt be kept alive by the nominal
voltage, that the power lines supply and it cuts out. Presto, you
have saved the power lines and equipment w/o having to shut the
power off. The JL is a sort of "self-reseting" lightning arrestor.

Now in a true TC circuit, the JL effect will never really appear. To
get the arc to rise, you need a constant source of current. A spark
gap driven TC is a pulsed device. Also, if you now consider the
spark gap to be the lossiest part in a DW TC, then you donīt want
to put any further "effort" into making it even more lossy. If the arc
starts to rise, I^2R losses skyrocket and your TCīs performance
will go down.

Coiler greets from germany,
Reinhard