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Re: Ignition Coils (fwd)

---------- Forwarded message ----------
Date: Wed, 11 Jul 2007 14:06:51 -0700 (PDT)
From: G Hunter <dogbrain_39560@xxxxxxxxx>
To: Tesla list <tesla@xxxxxxxxxx>
Subject: Re: Ignition Coils (fwd)

> Daniel,
>      I think putting an ignition coil across 120 V
> AC is asking for a pile 
> of molten copper (correct me if I'm wrong guys).

OK, I'll correct you.
> They are meant for 12 V or 
> so DC input (off a condenser, triggered by the
> distributer), and get HV out, 
> by operating at resonance (like a TC, using one off
> of turns ratio alone 
> doesn't amount to much).

In an old mechanical point & condenser car ignition
circuit, self-induction can boost the primary voltage
spike to 200v or so when the points open.  A modern
capacitive discharge ignition (CDI) can pulse the
ignition coil primary with as much as 400v!  Clearly,
the car ignition coil can tolerate primary voltages
way above 12v.  The 170v peak available from a 120vac
outlet is actually a bit tame by comparison.

Using a motor run cap in series and a standard 600W
lamp dimmer to pulse the current, I've used ignition
coils to fire a spark gap for minutes at a time with
no sign of undue heating or other stress.  I have also
run one for weeks at a time, 24/7, in an open-circuit
condition as an electric fence charger.  Again--no
harm to coil, cap, or dimmer.

I agree that 120vac operation of a car ignition coil
for the purpose of exciting a Tesla coil is a
misapplication of the part.  However, coilers
routinely use components and materials in applications
for which they were never intended. It comes with the
overall weirdness of this hobby.



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