The principle of the ignition coil

The usual ignition coil has two sets of coils inside, the primary coil and the secondary coil. The primary coil uses a thicker enameled wire, usually with an enameled wire of about 0.5-1 mm around 200-500 turns; the secondary coil uses a thinner enameled wire, usually with an enameled wire of about 0.1 mm around 15000-25000 turns. One end of the primary coil is connected to the vehicle's low-voltage power (+) and the other end is connected to the switching device (relay). One end of the secondary coil is connected to the primary coil, and the other end is connected to the output of the high-voltage line to output high-voltage electricity.

The ignition coil can turn the low-voltage electricity on the car into high voltage 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 ignition coil works differently from ordinary transformers, the working frequency of ordinary transformers is fixed 50Hz, also known as power frequency transformers, and ignition coils work in the form of pulses, which can be regarded as pulse transformers, which repeatedly store energy and discharge energy at different frequencies according to different speeds of the engine.

When the primary coil is connected to the power, a strong magnetic field is generated around it as the current increases, and the core stores magnetic field energy; When the switching device disconnects the primary coil circuit, the magnetic field of the primary coil decays rapidly, and the secondary coil induces a very high voltage. The faster the magnetic field of the primary coil disappears, the greater the current at the moment of current disconnection, and the larger the turn ratio of the two coils, the higher the voltage induced by the secondary coil.