Technical information The primary ignition is so called as it forms the first part of the ignition circuit. Through the ignition coil, it drives the secondary High Tension (HT) output. The primary circuit has evolved from the basic contact breaker points and condenser to the distributorless and coil-per-cylinder systems in common use today. All of these ignition systems rely on the magnetic induction principle.
Magnetic Induction This principle starts with a magnetic field being produced, as the coil's earth circuit is completed by either the contacts or the amplifier providing the coil negative terminal with a path to earth. When this circuit is complete, a magnetic field is produced and builds until the coil becomes magnetically saturated. At the predetermined point of ignition, the coil's earth is removed and the magnetic field collapses. As the field inside the coil's 250 to 350 primary windings collapses, it induces a voltage of 150 to 350 volts.
The induced voltage is determined by: · The number of turns in the primary winding · The strength of the magnetic flux, which is proportional to the current in the primary circuit · The rate of collapse, which is determined by the speed of switching of the earth path
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