Re: On sparks

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

Original poster: "by way of Terry Fritz <twftesla-at-uswest-dot-net>" <FutureT-at-aol-dot-com>

In a message dated 3/26/01 5:07:04 AM Eastern Standard Time, tesla-at-pupman-dot-com 
writes:

> 
>  Just to see what would happen, I thought to extend the function of my
>  128-cycle counter so as to interrupt the primary's excitation in bursts
>  of 128 cycles over the entire 7 ms duration.  400 us on, 400 us off, etc.
>  
>  The sparks appear identical in form--jagged & branched--but they are, of
>  course, less "fat" when interrupted.  But that they appear otherwise
>  identical tells me that each burst of sparks travels essentially the same
>  path during the entire series of 400 us bursts.  I suspect that it's the
>  heated air, along the path, that induces all the repeating sparks to
>  follow along. 

Ken,

That's an interesting test.  You seem to be implying that the sparks
are still the same length as before.  This would suggest to me that
the duration of the application of current to the arcs does not seem
to make them shorter, but just dimmer or thinner.  By reversing
this thought, it seems to suggest that applying current for a longer
duration would not make the spark longer either.  I'm assuming
that since the coil is off for half the time during a burst now, that
the total average current supplied to the arc is much less overall.
Are you thinking the same way?  Am I missing some point?

Maybe it's the peak currents, rather than the average currents
that are important in determining spark length?  Any thoughts
about this in light of your experiment?

For instance if you can channel the power you "saved" by
having the coil off during half the burst time, into higher peak
powers instead, that may make the sparks longer.  Since
the MOSFETS are only "on" half of the time now, they should
be able to handle higher peak currents without burning up.

John Freau