When talking about capacitors in relation to cars, first of all they have in mind the ignition system.
In it, capacitors began to be used when it was contact, and they are still being used.
In the classic ignition contact systemThe capacitor is connected in parallel to the breaker. The ignition coil (reel) is an autotransformer, the conversion coefficient of which is not so great. Therefore, when the contacts of the breaker are closed, when the voltage at its primary winding increases abruptly from zero to the voltage of the on-board network, the amplitude of the pulse produced by the secondary winding is not enough to break the candle. At the same time, energy in the form of a magnetic field begins to accumulate in the coil. When the contacts are opened, this energy is released, and a self-induction voltage appears on the terminals of the primary winding, which exceeds the voltage of the on-board network by almost 20 times. But the voltage for the current is not enough - we also need a closed circuit. Without a capacitor, it would form a battery and a spark between the contacts of the breaker, which would cause the latter to wear out badly. If a capacitor is connected in parallel to the breaker, the current flows through it. On the secondary winding of the reel, a voltage arises that exceeds the self-induction voltage by the transformation coefficient, which penetrates the spark gap of the candle.
Principles of operation of electronic ignition systemsAre different. In some of them, as in contact ones, the primary winding of the ignition coil, which is fed from the on-board network, commutes, only this commutation is made by a non-contact method. In others, the voltage of the on-board network is increased approximately 20 times by the converter beforehand. This voltage is used to charge the capacitor. At the moment when a spark is required, the capacitor closes onto the reel and discharges to it, then disconnects from it and is again charged from the transducer. In systems of the second type, sparks do not occur at the time of opening, but at the moment of closure.
The use of capacitors andAuxiliary components of the electronic ignition system. These are, for example, power filters, frequency-specifying circuits of converters, and in microprocessor systems - clock generators. Low-voltage capacitors of small capacities are used here, therefore they are small-sized. But for an uninterrupted operation of the ignition system and the engine as a whole, they are no less important. If any of them suddenly disappeared, the engine would immediately stop.