Ignition Coil: Description and Operation

The ignition coil is a transformer designed to increase primary voltage of 12 volts to at least 30,000 volts.

Coil View:

The ignition coil consists of a metal housing which accommodates metal plate jackets for reducing stray magnetic fields. The secondary winding is wound directly onto the laminated iron core and connected electrically to the center tower in the cap of the ignition coil via the core. Since the high tension is applied to the core, the core must be insulated by the cap and an additional insulator inserted in the base. The primary winding is located near to the outside around the secondary winding. The insulated ignition coil cap contains the terminals for the battery voltage and the connection for the DME control unit as well as the high-tension tower. The windings are insulated and mechanically locked in position with asphalt. Heat is dissipated through the metal plate jackets to the case.
The primary current which is switched on and off by the DME control unit flows through the primary winding of the ignition coil. The magnitude of the current is determined by the battery voltage at terminal 15 and the ohmic resistance of the primary winding.
The current flowing through the primary winding of the ignition coil produces a magnetic field in the coil. When the primary circuit is interrupted to the coil, the magnetic field collapses, and the movement of the magnetic field induces current in the secondary winding of the coil. Since there are many more turns of wire in the secondary winding than there are in the primary winding, the battery voltage is increased to the voltage necessary to ignite the combustion mixture.