Ignition Coil: Description and Operation

Ignition Coil Schematic Diagram:

PURPOSE
The Ignition Coil transforms battery voltage into ignition voltage and delivers it in the form of a high voltage surge to the secondary ignition components.

OPERATION

The ignition coil (located in the distributor) uses the principle of mutual induction to step up battery (low) voltage to ignition (high) voltage. The ignition coil contains two sets of copper wire windings around a soft iron core.
The primary winding is made of a hundred or so turns of a heavy gage wire. It is connected to the battery through the ignition switch (+) and to the ignition control module (ignitor) (-) so that current flows through it, thus creating a magnetic field.
The secondary winding is connected to the coil output tower through the iron core. It contains several thousand turns of wire wound directly onto the iron core. The ratio of the number of wraps in the secondary winding to the number of wraps in the primary windings determines the output voltage of the coil. The ratio is approx. 1 to 110.
When current flow in the primary winding is stopped (by the ignitor breaking the circuit ground), the collapse of the magnetic field causes a high voltage (20,000 volts or more) to be induced in the secondary windings.