The principle of automatic regulation of automotive generators
The automatic regulation principle of automotive generators mainly achieves voltage stability through electromagnetic induction and magnetic field current control. The following is the specific mechanism:
Electromagnetic induction regulation mechanism
The generator automatically adjusts its power generation according to the electricity demand. When the battery power is insufficient or high-power electrical appliances are used, the generator increases the power generation by enhancing the magnetic field current. When the battery is fully charged, the magnetic field current is automatically reduced, only maintaining the basic power demand.
Principle of voltage regulation
The magnetic flux is changed by automatically adjusting the magnetic field current to ensure the stability of the output voltage. When the generator's rotational speed changes, causing voltage fluctuations, the regulator detects an abnormal signal and adjusts the magnetic field strength by changing the excitation current, thereby restoring the voltage to the set range. For instance, when the rotational speed increases, reduce the excitation current to prevent overvoltage; when the rotational speed decreases, increase the excitation current to maintain voltage stability.
Different types of regulators
Youdaoplaceholder0 relay regulator : By controlling the on-off of the relay contacts to regulate the magnetic field circuit, automatic voltage regulation is achieved.
Youdaoplaceholder0 Electronic regulators (such as internal grounding type/external grounding type) : They use components like transistors and voltage stabilizing diodes to control the magnetic field current through circuit on-off.
This system can efficiently balance power generation and electricity demand, avoid energy waste and extend the service life of equipment.
The car generator is the main power source of a vehicle. Its function is to supply power to all electrical devices (except the starter) while the engine is running normally, and at the same time charge the battery.
Based on the three-phase stator winding of a common alternator, the number of turns of the winding is increased and the connection terminals are led out, and a set of three-phase bridge rectifier is added. At low speeds, the original winding and the added winding are output in series, while at higher speeds, only the original three-phase winding is output.
The working principle of the overall alternator
When the external circuit energizes the excitation winding through the brush, a magnetic field is generated, magnetizing the claw poles into N poles and S poles. When the rotor rotates, the magnetic flux alternately changes in the stator windings. According to the principle of electromagnetic induction, alternating induced electromotive forces are generated in the three-phase windings of the stator. This is the power generation principle of an alternator.
The rotor of a DC excited synchronous generator is driven by the prime mover (i.e., the engine) to rotate at a speed of n(rpm), and the three-phase stator winding induces an alternating current potential. If the stator winding is connected to an electrical load, the motor will output alternating current. The alternating current is converted into direct current through the rectifier bridge inside the generator and then output from the output terminal.
An alternator is divided into two parts: the stator winding and the rotor winding. The three-phase stator windings are distributed on the casing at an electrical Angle of 120 degrees to each other, and the rotor winding is composed of two pole claws. When the rotor winding is connected to direct current, it is excited, and the two poles form the N pole and the S pole. The magnetic field lines start from the N pole, pass through the air gap into the stator core and then return to the adjacent S pole. Once the rotor rotates, the rotor winding will cut the magnetic field lines, generating a sinusoidal electromotive force in the stator winding that differs by 120 degrees of electrical degree, that is, three-phase alternating current, which is then converted into direct current output by the rectifier element composed of diodes.
When the switch is closed, the current is first provided by the battery. The circuit is:
Positive terminal of the battery → charging indicator light → regulator contact → excitation winding → grounding → negative terminal of the battery. At this point, the charging indicator light will come on because there is current passing through it.
However, after the engine starts, as the generator's rotational speed increases, the terminal voltage of the generator also keeps rising. When the output voltage of the generator is equal to that of the battery, the potential at the "B" and "D" terminals of the generator is the same. At this time, the charging indicator light goes out due to the zero potential difference between the two ends. It indicates that the generator is operating normally and the excitation current is supplied by the generator itself. The three-phase alternating current electromotive force generated by the three-phase winding in the generator is rectified by a diode and then outputs direct current to supply power to the load and charge the battery.
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