Re: Quenching

In a message dated 98-12-11 00:24:10 EST, you write:

<< Original Poster: "Marco Denicolai" <Marco.Denicolai-at-tellabs.fi> 
> In particular to Terry Fritz:
> If my big TC resonance frequency is, say, 62 kHz, its period is 1/62000 =
> 16 us. Two things I don't understand:
 >- you have always been telling that, for optimal operation, the spark gap
>must quench just after the primary first oscillation period i.e. 16 us
> after the bang start. (I don't remember how do you call that "period"). If
> I use a rotary gap, what happens in terms of performance if I run fast,
> small electrodes ---> spark time less than 16 us?


You want to quench at the first notch which is different than the first
oscillation.  The notch will occur after a number of oscillations when
all the energy has transfered from primary to secondary.  By quenching
here, you trap all the energy in the secondary.  The number of oscillations
that occur before the notch depends on the value of k.  (At really tight 
values of k, the first oscillation and the first notch would be the same,
but you'll never be able to quench at that point with such tight k values
using a rotary gap.)

It's hard to build a rotary gap that will forcibly quench at a certain time,
generally the mechanical dwell time is longer than the quench time, so
quenching occurs due to energy depletion from the primary and 
secondary.  When figuring the mechanical dwell time of a rotary, you
must take into consideration the "overlap" time of the electrodes, this
will make the dwell time longer.  Although in a large machine running
at a low frequency, it may be possible to forcibly break the arc.

You don't have to worry about quenching too fast with a rotary, you'll
never do it.  But if you somehow could, yes quenching at the first
oscillation would fail to transfer all the primary energy to the secondary.

If you fail to quench at the notch, energy will transfer back into the 
primary, then back into the secondary, etc, and losses will be higher
mostly due to excessive gap losses.  However, tests have shown 
similar spark lengths whether quenching occurs on 1st, 2nd, or 3rd
notch in many cases.  There is some evidence and speculation that
the longer "activity" time and/or multiple pulses that occurs with a
2nd or 3rd notch quench, is actually helpful.

John Freau

> - If after a certain time the gap quenches (i.e. opens) how current can
> keep flowing into the primary? How the primary can still oscillate? Does it
> do it through all the tank supply (across the spark gap)?
> - doesn't a limited discharge time ( < 16 us) of the primary capacitor mean
> also that I don't use all the energy stored in the primary capacitor for
> the bang?