Working Principle and Classification of Ignition Coils

Ignition coil is one of the key parts of engine ignition device, which provides sufficient energy for spark plug to generate enough electric spark and improve engine performance. The car ignition coil is mainly composed of primary coil, secondary coil and core.

Ⅰ. Working principles of ignition coils

1. Structural features:

General ignition coil inside the primary and secondary two groups of coils, the primary coil is usually composed of about 0.5-1 mm enameled wire wound about 200-500 turns; The enameled wire of the secondary coil is generally wound with enameled wire of about 0.1 mm for about 15,000-25,000 turns.

One end of the primary coil is connected with the positive power supply of the vehicle, and the other end is connected with the switching device (breaker). One end of the secondary coil is connected with the primary coil, and the other end is connected with the output end of the high voltage line to output high voltage.

2. Principle:

When the primary coil is connected to the power supply, with the growth of the current, a strong magnetic field is generated around, and the magnetic field energy is stored in the core; When the switching device disconnects the primary coil circuit, the magnetic field of the primary coil rapidly decays 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 disconnection, the greater the turn ratio of the two coils, the higher the voltage induced by the secondary coil, from low to high voltage is thus converted.

Similar to a common transformer, the ignition coil has a large turn ratio between the primary and secondary coils, turning the low voltage into high voltage on the car. The difference is that it repeatedly stores energy and releases energy at different frequencies according to different engine speeds, and it works intermittently.

Ⅱ. Classification of ignition coils

The commonly used ignition coil is divided into two forms: open magnetic circuit ignition coil and closed magnetic circuit ignition coil.

1. Open the magnetic circuit ignition coil

The ignition coil with open magnetic circuit is made of electromagnetic mutual inductance principle. Its structure is mainly composed of the primary coil and secondary coil on the iron core, the shell and the additional resistance outside. The magnetic circuit ignition coil can be divided into two terminals and three terminals.

2. Closed magnetic circuit ignition coil

A closed magnetic circuit ignition coil that wraps both primary and secondary windings around a mouth or Japanese shaped core. The magnetic flux generated by the primary winding in the iron core, through which a closed magnetic circuit is formed.

The advantages of the closed magnetic circuit ignition coil are less magnetic leakage, small magnetic resistance of the magnetic circuit, thus small energy loss and high energy conversion rate. Moreover, the closed magnetic circuit ignition coil adopts thermosetting resin as insulation filler, and the shell is hot-melt plastic injection molding. The insulation and sealing properties of the closed magnetic circuit ignition coil are better than those of the open magnetic ignition coil.

Small size, can be directly mounted on the distribution cover, not only compact structure, and eliminate the high voltage wire between the ignition coil and the distribution, and can reduce the secondary capacitance, so widely used in electronic ignition system.

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