A brief description of the structure and working principle of the car charging system

The car charging system comprises a generator, battery, voltage regulator, charging indicator, related wires, etc.

1.Generator: The generator is the main power source of the car’s electric equipment. During the normal operation of the car, the generator supplies power to other electrical equipment except the starter and charges the battery. In other words, when the engine is running normally, almost all the electricity on the car is provided by the generator; when there is power left, the generator will charge the battery. The power of the general car generator is 0.8~1.5 kW, which can meet the car’s electricity demand in most cases, and is supplemented by the battery when the power generation is insufficient. Furthermore, in some small-displacement engines, when the generator generates more power and higher load, the engine will shake due to increased load, the engine will automatically increase the speed to enhance the engine power.

Most of the generators used in automobiles are silicon rectifier three-phase alternators, which use silicon diodes as rectifiers to convert alternating current into direct current. Its main structure comprises rotor, stator, brush and slip ring mechanism, three-phase bridge rectifier, bearings, fan and front, rear end caps, etc. The rotor is used to generate a magnetic field, the stator is used to send current, and the rectifier converts three-phase AC into DC pulsating voltage. Generator power generation increases with the engine speed.

2. Bbatteryis the largest electrical equipment on the car. Its main role is in the engine start, to the starter, ignition system, and other major electrical equipment power supply; in the engine does not run or low-speed operation, to a variety of electrical equipment power supply. When too much electrical equipment, power consumption exceeds the power supply capacity of the generator, the battery assists the generator to a variety of electrical equipment power supply. In addition, the battery has the role of stabilizing the voltage of the power supply system. It is equivalent to a large capacitor, absorbing the instantaneous overvoltage in the circuit to protect the electrical equipment.

Many people think that the battery is the main power supply of the car, but in fact, it is not. The generator is the real power supply of the car. When the engine works normally, the output voltage of the generator is higher than the voltage of the car battery, the generator to all electrical equipment (except the starter) power supply, while charging the battery; and the battery only when the engine starts, only with its internal storage of electrical energy to drive the starter, usually it is done as an electrical appliance exists.

3, voltage regulator: voltage regulator is used to adjusting the generator output voltage so that the generator output voltage is maintained between 13.8-14.4 volts. Because the generator’s output voltage is rising with the engine speed, if the engine speed is too high, resulting in generator output voltage is too high, it will burn the car’s electrical system and some precision electronic components. With a voltage regulator, you can avoid these problems. Nowadays, voltage regulators in cars are electronic, most of them are integrated inside the generator, and only a few are external. The vast majority of generator failure is caused by voltage regulator failure.

4, charging indicator system: charging indicator system mainly refers to the voltmeter or charging indicator on the dashboard. They are used to indicate whether the generator’s working status is normal. If the charging indicator lights up or the voltmeter pointer is lower than 24V when the car is running, it means that the generator is not charging or the charging amount is too low, and the charging system needs to be overhauled.

The working principle of the car charging system is as follows: when we turn on the ignition switch, the battery will provide excitation current to the rotor of the generator, and the rotor will produce a magnetic field; then the engine will start, driving the generator to run, and the stator winding will cut the magnetic lines of the rotor winding, producing three-phase AC current, which will be turned into DC power after silicon rectification and output to the outside; at this time, because the generator speed is low, its excitation current is provided by the battery. As the generator speed gets higher and higher, the power generation becomes larger and larger, the rotor winding current is provided by the generator’s own current. This situation is called “self-excitation.”

When the engine works normally, the generator also runs at high speed with the engine, sending out electrical energy to the car’s electrical equipment, and the excess power is used to charge the battery. When the battery is full, the voltage regulator disconnects the excitation current of the rotor, and the generator stops generating electricity; when the battery voltage decreases to a certain value, the voltage regulator reconnects the excitation current, and the generator resumes generating electricity. This process is repeated repeatedly to ensure the normal operation of the car’s electrical equipment and keep the battery in a fully charged state. In order to ensure that the car can generate electricity even at low speed, the general generator speed is 2.5~3 times the engine speed, so even if the engine is idle, the generator can generate electricity normally.

The common failures of car charging systems are not charging, overcharging and undercharging, etc. The causes of the failures are just two: poor line contact and generator failure. Generally speaking, the generators nowadays are highly integrated and cannot be disassembled and repaired under normal circumstances but can only be replaced as a whole. The car charging system in the use of the process shall not use the generator output instantaneous grounding (latching) method (pilot method) to determine whether the generator generates electricity and shall not remove the battery and other major electrical equipment when the generator is generated is running at high speed. So as not to produce surge voltage breakdown of precision electronic components. In daily maintenance, we must often check the connection between the generator and the battery to ensure that the connection is solid and reliable, with no rust at the joints. In addition, we must often check the tension of the generator belt. If the belt is too loose, it will cause the generator speed to be too low for power generation. If the belt is too tight, it is easy to cause damage to the belt and generator bearings.


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