V = L dI/dT
WD8JJA
----- Original Message -----
From: "Tom Rauch" <w8ji@contesting.com>
To: <amps@contesting.com>; "Radio WC6W" <wc6w@juno.com>
Sent: Friday, March 07, 2003 6:32 AM
Subject: Re: [Amps] Arcing
>
> ----- Original Message -----
> From: "Radio WC6W" <wc6w@juno.com>
>
> > 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.
>
> Anyone checking a power transformer with a high-current ohmmeter knows
this
> effect well. When you pull the meter leads, you are lucky of you don't
blow
> the meter out or get knocked on your rear!
>
> Ford ignition coils, for the high-energy Duraspark system, which
essentially
> was a solid-state spin-off of a conventional points system, used a 38 or
40
> :1 turns ratio ignition coil. Run outside and grab the ignition lead on a
> running Ford engine from the 70's through 90's, and see if that feels
> anything like 400 volts!
>
> GM used a similar HEI system, with turns ratios in the same general area.
As
> a matter of fact you can buy a beefy replacement coil at:
>
> http://www.taylorvertex.com/catalogindex/2002TV78.PDF and up the
ratio
> to 70:1 to get 40kV spark. The HEI ignition applies less than 10v to the
> coil primary, and again is a solid state version of a points system.
>
> Your argument about the capacitor argues against your claim voltage only
> relates to turns ratio. If the voltage was only 10 volts or so upon
release,
> you would never have an extended points arc during release. The primary
has
> a 1:1 ratio with itself, yet the peak voltage can be hundreds of volts.
> Flyback transformers, switching supplies, and even tank circuits all go
into
> this mode whenever applied energy is not removed over an equally long
period
> of time. The voltage increases until the stored energy is somehow
> dissipated.
>
> 73 Tom
>
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