Transformers

[garfield at pilgrimhouse.com]

On Fri, 29 May 1998 13:14:48 -0400, "Bruce Plecan" <nacelp at bright.net>
wrote:

>So then the primary side of the ignition system should be designed to
>take a "full hit" if the secondary goes open?.  So if like a diode is at
>the "final drive" of the ignition coil driver is needs to clip the feedback,
>and be able to withstand 30,000+ v, right?

Umm, nope it's not quite that bad, *usually*. If you have a coil that
leaks HV into the primary, normally that will hopefully be gobbled up by
a transorb on the driver's output, a few times, but if it's a real solid
repeated arc-over into the primary, you're probably lookin at an entre'
of crackin toast somewhere; the day2day protection on the primary side
from the inductive back-emf of opening the primary is normally designed
just for the primary side excursions which are in the hundreds of volts
if unsuppressed, not tens of thousands.

That's why the systems aren't really designed to "certainty of
survivability" if you leave the secondaries completely open. Instead,
the solution is "don't do that!". Ya know, the side of medicine they
refer to as "prevention". Heh. The better the coils are designed and
built, the closer they come to ideal personal lightning generators (ya
know the things Dr. Fronkensteen used on his lab rats), and with the
field collapsing instantly and more efficiently, the ONLY thing limiting
the actual PEAK of the HV spike is something breaking down somewhere.
We're talking execution chambers here, dudes. Nobody designs primary
side circuits to "certain survivability" from a rapid-fire series of
lightning strikes!

>  Autotransformer has nuttin to do with automotive useage, whodda
>thunk that.............

Yeah, ain't English wunnerful. A veritable fertile compost heap of
ambiguity! ;)

Gar