Re: Placement of Ballast Resistor

Posted by Dwight - VA on January 18, 2006 at 00:08:45 from (65.254.173.253):

In Reply to: Placement of Ballast Resistor posted by Thomas Donahy on January 15, 2006 at 07:27:04:

Good discussion.. some of my thoughts..

The ballast resistor should always be connected in the primary circuit of the coil.

To put the ballast resistor in the secondary circuit would affect the time constant charging of the condenser (capacitor), which is essentially in parallel with the breaker points, and is the only path for current from the coil to ground when the points open. Changing the time constant will change the engineered relationship between the coil and the condenser, probably resulting in an under-performing spark.

The ignition coil IS an autotransformer, meaning the primary and secondary share some of the same windings and no part of the internal windings should be grounded to the coil shell or the coil itself would be grounded and thus useless. The high voltage spark comes from a condition in the autotransformer called inductive kickback when the points open.

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