Geometry vs Quench ?
Sent: Wednesday, September 24, 1997 3:41 AM
Subject: Re: Magnetic quenched gaps
In a message dated 97-09-23 22:10:45 EDT, you write:
> Has anyone experimented with rotary gap electrode Geometry vs Quench ?
> Could electrode geometry be designed such that extinction is naturally
encouraged >to ocurr after the first node -- make them longer (to retain
xsectArea for current and >heat) and thin to present conductor for a short
arc time at optimum cycle times ? >(or perhaps in conjunction with
> A thought from Dale.
You bring up an interesting issue. It may be Glascoe's book which
states that the rotary electrodes, as they approach each other, can
produce a pressure wave which helps to quench the spark.
It must be realized that the spark-gap arc quenches well before the
elecrodes pass each other by. There is often no correlation between
actual quench times and mechanical dwell times. This is often
misunderstood by coilers. For instance, the mech. dwell time could
be 200 uS, but the actual quench time might be 20 uS. The gap will
quench when it runs out of energy, and this is often way before the
mech. dwell time is realized. Interestingly, in some cases, a longer
mech. dwell time may result in a shorter actual quench time. This is
because the large electrodes that are used for a long mech. dwell time
may run cooler and promote faster quenching.
Regarding your suggestion of using long narrow electrodes for more
contact area, Lou Balint (not on net) has just built such a gap, and
testing will begin shortly. But any advantage will come only from the
large contact area, not from a short mech. dwell time. Lou is also
using air blowers in this gap, but has not yet added magnetic quenching,
I don't know if he'll try magnetic quenching.
Generally, rotaries do not quench by pulling out and stretching the arc
to promote quenching, rather, the arc quenches while the electrodes
are still lined up. In some cases, the arc will quench before the electrodes
even line up...they will quench as the electrodes are still approaching.
It is possible that some particular electrode geometry might assist in
the quenching process. More work needs to be done.