When talking about capacitors in relation to cars, they primarily mean the ignition system. In it, capacitors began to be used when it was contact, and are still used.
Instructions
Step 1
In the classic contact ignition system, the capacitor is connected in parallel with the breaker. The ignition coil (bobbin) is an autotransformer, the transformation ratio of which is not that great. Therefore, when the contacts of the breaker are closed, when the voltage on its primary winding abruptly increases from zero to the voltage of the on-board network, the amplitude of the pulse generated by the secondary winding is not enough for the breakdown of the spark plug. At the same time, energy begins to accumulate in the coil in the form of a magnetic field. When the contacts open, this energy is released, and a self-induction voltage appears at the terminals of the primary winding, which exceeds the voltage of the on-board network by almost 20 times. But the voltage for the occurrence of current is not enough - a closed circuit is also needed. Without a capacitor, it would be formed by a rechargeable battery and a spark between the contacts of the breaker, which would cause the latter to wear out a lot. If a capacitor is connected in parallel to the breaker, the current flows through it. On the secondary winding of the bobbin, a voltage arises that exceeds the self-induction voltage by the transformation ratio, which breaks through the spark gap of the candle.
Step 2
The principles of operation of electronic ignition systems are different. In some of them, as in the contact ones, the primary winding of the ignition coil, powered from the on-board network, is switched, only this switching is performed in a non-contact way. In others, the voltage of the on-board network is increased in advance by approximately 20 times by the converter. This voltage charges the capacitor. At the moment when a spark is required, the capacitor is closed on the bobbin and discharged onto it, then disconnected from it and again charged from the converter. In systems of the second type, sparking occurs not at the moment of opening, but at the moment of closing.
Step 3
Capacitors are also used in auxiliary units of electronic ignition systems. Such are, for example, power filters, frequency-setting circuits of converters, and in microprocessor systems - clock generators. Low-voltage capacitors of small capacities are used here, so they are small-sized. But for the smooth 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.
