Van S. Griffin writes:
>Scions,
> The question of typical discharge currents in a typical plug
>discharge has come up and I was wanting to shore up my memory (OK, it's
>degenerated into an educated guess); does 150 mA sound about right at the
>peak current or is it more? With all the ignition topic traffic,
>someone must have this on the top of his noggin. No sig file, Van
Well lets do some math here:
The coil draws about 1.5 Amps when running (a number I read in the Bentley
manual). The rule for transformers is the current ratio (primary to
secondary) is the inverse of the voltage ratio (primary to secondary).
Consequently, the current to the spark plug would be:
1.5 Amp x 12v / 25,000v = 720 uAmps or .72 mA.
Assuming 25,000 volt spark voltage.
Dave Massey
St. Louis, MO USA
P.S. BTW this is obviously wrong because the condenser in the primary
circuit creates a tuned circuit and when the points open the voltage
across primary windings is well in excess of 12 Volts. I don't know what
it is but I could drag my oscilloscope out to the garage and find out.
P.P.S. I seriously doubt the current is as high as 150 mA. This could
prove to be too costly in our litigious society. Heart fibrillation
occurs in the 100 - 200 mA range. I also doubt it is less than 1mA
because 1mA is the threshold of feeling. In other words one can not
feel currents under 1mA and I can attest to the fact that one can feel
the current coming out of the coil!
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