Re: Transformer Protection? (fwd)

---------- Forwarded message ----------
Date: Sun, 07 Dec 1997 21:11:29 +1100
From: Peter Electric <elekessy-at-macquarie.matra-dot-com.au>
To: Tesla List <tesla-at-pupman-dot-com>
Subject: Re: Transformer Protection?

Tesla List wrote:

> From:   Alfred A. Skrocki[SMTP:alfred.skrocki-at-cybernetworking-dot-com]
> Sent:   Sunday, November 30, 1997 8:53 AM
> To:     Tesla List
> Subject:        Re: Transformer Protection?
> On Monday, December 01, 1997 3:56 PM D.C. Cox
> [SMTP:DR.RESONANCE-at-next-wave-dot-net]
> > to: Alfred & Jim
> >
> > The intended use of an automobile ignition coil is to fire a spark
> across a
> > gap of .040 inches or less.  Firing across a 1/2 to 1 inch airgap is
> quite
> > another matter for the coil.  Many coils produce higher than
> standard
> > potentials as they have to fire under high cylinder pressures,
> > never-the-less, producing a longer arc with the coil will require
> some
> > protection.  We made several such systems back in the late 60's and
> the
> > coils didn't last too long without some protection from spikes.

This is not strictly correct. While the gap maybe .040", when the spark
plug is subjected to highly compressed fuel and vapor mixture, the
voltage across the gap will rise to something approaching the 1/2"
airgap value before firing.

I have also built solid state drivers for these coils using MJ2955's in
the late 60's and I still have one of these in my workshop, still
throwing 1" long sparks!


Peter E.