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Re: GM HEI Coil Autopsy

Terry Fritz wrote:
> 
> Hi Ed,
> 
>         As a post I sent to the list tonight descibed...  I am now
hitting the
> coils with 1400 volts, 1.6 jouls, 180+kV output voltage and am getting 12.2
> inch sparks!  My brand new coil is still alive for tomorrows testing :-))
> This is a young coils sport!!
>         I really thought core saturation was what was keeping the "core
in place"
> coils from performing.  Perhaps there is something else that needs to be
> considered.  I haven't mentioned it on the list yet, but tuning these
> things in a Tesla coil configuration is really strange.  They always like
> to tune to 10kHz despite variations in there inductances and such from coil
> to coil.  also I suspect that primary to secondary capacitance plays a
> major role in this application.  Many mysteries as to what is going on
> inside these coils!
>         I hope to get the details of how to reproduce this out soon.  I
started
> this out as a simple beginners coil project.  However, it is now getting
> pretty darn dangerous!  I have to separate the beginner's version from the
> no holds barred get the longest spark version.  This has really turned into
> a major project!!
> 
>         Terry
> 
> At 08:17 PM 11/17/98 -0800, you wrote:
> >Terry:
> >
> >       I haven't seen evidence of core saturation when pulsing the
primaries
> >to between 550 and 600 volts peak, as the pulses are quite short.  Also,
> >the cores don't heat up much with runs of up to 30 minutes.  Should
> >publish the waveforms, but don't have a digitizing scope.  As for
> >defects in the epoxy casting, I'm sure you're right.  However, the only
> >coil I have lost to date was lost due to breakdown between the inside of
> >the secondary and the primary.  Haven't had any other primary short, and
> >no secondary shorts either.  I've run coils in air at high enough
> >voltage that they sparked between the secondary terminal and the
> >primary.  These are old coils, certainly having had a long, hot life in
> >their intended use.  As you say, if one has a bunch of old coils around
> >....... one can experiment with them at quite low cost.  Never thought
> >of removing the core and running as you are.  That really puts a stress
> >on the secondary!
> >
> >Ed
> >
> >

	At some point in your investigations please give us a schematic of your
driver circuit.  Sounds quite interesting!

Ed