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Distributor type Ignition System

As the name suggests, it consists of a distributor located at the nerve centre of the ignition system. The distributor triggers the ignition coil to generate the required high voltage. A distributor cap with a rotor is provided which directs the high voltage supply to the spark plug lines in firing order.

How is the high voltage supply generated?

When the ignition key is switched ON, a 12 V electrical energy is supplied from battery to the ignition coil via a primary resistor. The ignition coil has primary copper windings of more than 100 turns before exiting the negative terminal of the coil.

From the ignition coil, the current is supplied to the distributor which has two contact breaker points. One of the contact breaker points is fixed, while the other is movable and mounted on a spring loaded arm. The spring loaded arm rides on a distributor cam with lobes (number of lobes = number of cylinders in an engine). The speed of the cam is half the speed of the engine crankshaft.

When the two contact points are in contact, the current goes directly to the ground and this builds a strong magnetic field inside the ignition coil. The rotation of cam intermittently opens and closes the contact points. When the points are open, the current supply to the ground is interrupted and the magnetic field suddenly collapses in the coil. This collapse in magnetic field results in a surge of electrical voltage in the secondary winding. The high voltage supply is then supplied to the distributor cap via high tension wire.