Re: Re: How does battery ignition work?

Posted by RAB on May 01, 2003 at 12:46:50 from (195.93.50.7):

In Reply to: Re: How does battery ignition work? posted by Sam#3 on May 01, 2003 at 08:19:48:

Nearly right.
The coil primary (coil energy) will try to discarge thru the points as the magnetic flux generated by the interruption of the primary current(points opening). This may be of the order of a few hundred volts, but enough to arc at the points and transfer metal from one point to the other. The condensor is there to prevent this happening until the points are far enough apart so the air gap (high resistance) is able to resist the arc - just a few thou. is required. That is all the condensor does, but it is very important as it stops the points burning and prevents energy loss from the coil primary back through the points. The voltage spec. of this component is probably in the region of 500V. The secondary coil produces a step up voltage of around 15k, enough to jump a spark plug gap easily.

It may be worth noting that the current build in a coil is exponential - means the current increase in the coil winding produces a magnetic field which in turn resists that increase in current (takes a long time relatively to get to Ohm's law current) and so the points are designed to stay closed for as long as possible (dwell angle) to maximise the energy in the coil. This is not so important for tractors at, say, 2000rpm but for a V8 at 6000rpm it is very important!(thats one reason why elctronic systems were first introduced)
Sorry for such along post - the Ketteringham system was a masterpiece in its time, but is probably long past its sell by date now.
Regards, RAB

Follow Ups:

• Re: Re: Re: How does battery ignition work? Steve 05:49:35 05/02/03 (2)
  • Re: Re: Re: Re: How does battery ignition work? RAB 02:37:58 05/03/03 (1)
    • Re: Re: Re: Re: Re: How does battery ignition work? steve 18:57:44 05/04/03 (0)

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