>Hi Tom
>
>On Thu, 6 Mar 2003 10:09:16 -0500 "Tom Rauch" <w8ji@contesting.com>
>writes:
>
><snip>
>
> It all sounded good until you got to here... even though it is way off
>topic and...
> I'm glad that someone recalls when sparks were made in the old way!...
>it begs correcting.
>
>
>> Many people think, for example, the peak ignition voltage in anignition
>> system is set by the turns ratio in the ignition coil. That isn't true at
>> all, the peak voltage is many times the actual turns ratio would
>produce.
>
> Wrong.
>
> The turns ratio works just as expected in that application. The
>secondary voltage is equal to the primary voltage multiplied by the turns
>ratio.
Indeed, Marv. I confirmed this with an oscilloscope. The primary V
spike is generated by the collapsing field when battery current flow
stops in the primary -- i.e., the ignition contact opening, in days of
yore. Even though the battery is only 12v, when the flow of current in
the primary stops, the collapsing magnetic field induces a few hundred
volt spike in the primary. The points' Capacitor (Typ 0.15uF) and
L-primary resonate typically c. 100KHz in a '69 BMW. The spike rings the
L-C resonant circuit for a few cycles, and the typical 100 to 1 step-up
iratio increases the few hundred V spike by a factor of 100.
>
> Note: the primary voltage is not always equal to the battery (or
>system) voltage. Do I have to explain the whole process here or... just
>let this comment initiate a worldwide ringing? :-)
>
>> Remove the capacitor in an old-style ignition, and watch the voltage
>> drop!
>
> Only because the points, which are not opened instantaneously, will
>arc (gosh, there's that arcing again...) thereby stealing the stored
>ignition coil energy out of the primary instead allowing it to exit the
>secondary where it can help make smog.
>
>
>73 & Good evening,
> Marv WC6W
>
>
>
>
>
>
>
>*
>
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- R. L. Measures, a.k.a. Rich..., 805.386.3734, AG6K,
www.vcnet.com/measures.
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