A typical ignition coil has two sets of coils, a primary coil and a secondary coil. The primary coil is made of a thicker enameled wire, usually about 0.5-500 mm with an enameled wire of about 0.5-1 mm; the secondary coil is made of a thin enameled wire, usually about 15,000-25,000 inches with an enameled wire of about 0.1 mm. One end of the primary coil is connected to the low voltage power supply (+) on the vehicle, and the other end is connected to the switch device (disconnector). One end of the secondary coil is coupled to the primary coil, and the other end is coupled to the output of the high voltage line to output high voltage power.

The reason why the ignition coil can turn the low voltage of the vehicle into a high voltage is because it has the same form as the ordinary transformer, and the primary coil has a larger turns ratio than the secondary coil. However, the working mode of the ignition coil is different from that of the ordinary transformer. The working frequency of the ordinary transformer is fixed 50Hz, also known as the power frequency transformer, and the ignition coil works in the form of pulse. It can be regarded as a pulse transformer, which is different according to the engine. The speed is repeatedly stored and discharged at different frequencies.

When the primary coil is turned on, a strong magnetic field is generated around the current, and the core stores the magnetic field energy. When the switching device disconnects the primary coil circuit, the magnetic field of the primary coil is rapidly attenuated, and the secondary coil is Will induce a very high voltage. The faster the magnetic field of the primary coil disappears, the larger the current at the moment of current disconnection, and the higher the turns ratio of the two coils, the higher the voltage induced by the secondary coil.