Mark,
This site has a fairly involved explanation of the effects of a condenser in
an ignition circuit. The part about the oscillation is interesting. I, for
one, never thought about that before:
http://www.mgb-stuff.org.uk/wn_ignitionframe.htm
Gary
'73
----- Original Message -----
From: "Mark Anderton" <andertonm@cox.net>
To: "Navarrette, Vance" <vance.navarrette@intel.com>; "Jim Swarthout"
<jswarth1@tampabay.rr.com>; <6pack@autox.team.net>
Sent: Monday, June 30, 2003 5:35 PM
Subject: Re: Ballast resistor question
> I think the condensor (capacitor) actually provides the path through which
> the current flows when the coil magnetic field is collapsing. If I
recall,
> you take it out and the car doesn't run.
>
> Mark Anderton
> 72 TR6
> Virginia Beach
> http://members.cox.net/andertonm/car_stuff.html
>
> ----- Original Message -----
> From: "Navarrette, Vance" <vance.navarrette@intel.com>
> To: "Jim Swarthout" <jswarth1@tampabay.rr.com>; <6pack@autox.team.net>
> Sent: Monday, June 30, 2003 7:39 PM
> Subject: RE: Ballast resistor question
>
>
> > Jim:
> >
> > You have it correct.
> >
> > The coil is an inductor, which means that energy is stored in the
> > magnetic field surrounding the core.
> > When the points open, the magnetic field collapses, and this stored
> > energy appears as a voltage across the output (*AND* the INPUT!!) The
> voltage
> > will go as high as it needs to in order to dump the stored energy in the
> form of
> > current. Hopefully this energy appears across the plug gap, and in turn
> ignites
> > the mixture in the cylinder.
> > Were it not for the condenser across the points, some (most?) of the
> stored
> > energy would appear as an arc across the *points*. This would divert
> energy from the
> > plugs (bad) and burn the points (also bad). The condenser prevents the
> energy from
> > being wasted and breaking delicate stuff that we would like to keep
around
> for a while.
> > The ballast resistor, on the other hand, is used to make the car start
> more
> > easily. It does this by allowing a 6 volt coil to be used. When the car
is
> cranking,
> > the battery is only delivering 6-7 volts. By using a 6 volt coil we get
a
> hotter
> > spark than from a 12 volt coil (at least while cranking).
> > When the motor is running, a 6 volt coil would overheat, and deliver so
> > much voltage that you would have flashover, misfiring, etc. So the
> ignition
> > switch is wired to hook the ballast resistor in series with the coil
after
> the
> > motor starts. This in turn drops the coil primary voltage down from the
> > battery voltage (now at 12 volts since the starter motor is no longer
> drawing current)
> > to the 6 volts it is designed for. You get the best of both worlds with
> > a ballasted coil. Un ballasted coils deliver a weaker spark while
> cranking, because they
> > are operating at half their rated primary voltage.
> >
> > Cheers,
> >
> > Vance
> >
> > ---------------------------------------
> > The most likely way for the world to be destroyed, most experts agree,
is
> > by accident. That's where we come in; we're computer professionals. We
> > cause accidents. - Nathaniel Borenstein
> >
> >
> >
> > -----Original Message-----
> > From: Jim Swarthout [mailto:jswarth1@tampabay.rr.com]
> > Sent: Monday, June 30, 2003 4:18 PM
> > To: 6pack@autox.team.net
> > Subject: RE: Ballast resistor question
> >
> >
> > Hmmmm,
> >
> > I had always assumed that the ,(capacitor), condenser prevented a
> > current overload at the points? Current causing the pitting of the
> > points?
> >
> > Occasionally I'm wrong!
> >
> > Anyone care to describe how an ignition coil works? After-all we are
> > converting 12V to 25,000V
> >
> > Jim Swarthout
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