Structure and Principle of Automobile Alternator

The automobile generator is the main part of the automobile power supply, which is responsible for supplying power to the components and charging the battery when the vehicle is running. Automobile generators can be divided into direct current generators and alternating current generators. Since alternating current generators are superior to direct current generators in many aspects, direct current generators have been eliminated. All automobiles currently use alternating current generators. This article focuses on the basic principles and structure of Alternator for trucks.

1. The basic principle of automobile alternator

Automobile alternators are also based on the principle of electromagnetic induction. When the magnetic flux is cut by a conductor moving in a magnetic field, an induced electromotive force is generated in the conductor. If we try to make the magnetic flux and the conductor produce relative cutting motion, the electromotive force can be generated in the conductor. This phenomenon is called "electromagnetic induction". The basic principle of the generator is the electromotive force generated by electromagnetic induction to generate electrical energy (voltage and current). Although a single conductor moving in a magnetic field can generate electromotive force, it is very small. If the two conductors are connected end to end, a secondary electromotive force will be generated, resulting in a double electromotive force. When a conductor in the form of a coil rotates in a magnetic field, it will generate a large electromotive force, thereby forming voltage and current. Based on this principle, the generator rotates the coil in a magnetic field to generate electrical energy, and the generated current is an alternating current that changes in size and direction.

As the coil generates more power, the coil generates heat more easily due to the action of the current. Therefore, installing the coil on the outer layer of the generator is beneficial for cooling. Therefore, all AC power generating coils (stator core) is in the outer layer, and the rotating magnets (rotor core) are in the coil.

Alternator For Trucks

2. Main functions of automobile alternator

01 power generation

The rotation of the engine is transmitted to the pulley with a multi-slot belt, and the electromagnetic rotor is rotated to generate an alternating current in the stator coil.

02 rectification

Because the electricity generated in the stator coil is alternating current, it cannot be used for direct current electrical devices installed on vehicles, so the rectifier is used to convert alternating current into direct current.

03Adjust the voltage

The regulator is used to adjust the voltage of the generator, and the voltage can be kept stable even when the generator speed or load changes.

3. Generator structure

It is mainly composed of rotor, stator, brush, rectifier, front and rear cover, fan, pulley, etc.

01 Rotor

The function of the rotor is to generate a rotating magnetic field. The rotor is composed of claw poles, yokes, field windings, slip rings, and rotor shafts, as shown in the figure.

02 stator

The stator is also called the armature. Its function is to generate alternating current, which is composed of the stator core and the stator winding.

03fan

It is installed on the rotating shaft outside the front cover to cool the generator when it is working.

04 Rectifier

The function of the rectifier is to convert the three-phase alternating current generated by the stator winding into a direct current output; secondly, it can prevent the current of the battery from flowing back to the generator. It generally has six silicon diodes connected to form a three-phase bridge full-wave rectifier circuit.

05 Brush

The brush is used on the commutator or slip ring as a sliding contact body for introducing and exporting current. It has good electrical, thermal, and lubricating properties, and has a certain mechanical strength, and the instinct of commutation sparks.

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