Car dynamo (generator): its components, function, how it works, and types? (2024)

The dynamo or the generator is one of the most important components of the car. For the car to work, it needs electricity, so there is a car battery that is the main source of electricity in the car, but it is nothing more than a store of electricity. This store will run out by use, so the car battery is designed of the rechargeable type.

The battery is recharged, but the battery does not charge itself, and here it was necessary to have a charging system, this system is the dynamo and it takes advantage of the movement of the engine when it rotates and converts it into electrical energy that charges the car battery and for this reason the battery continues to work for years.

In this article, we will learn more about the dynamo of the car, how it works, what its components are, and whether the dynamo in all cars is of the same type, or are there different types of dynamo?

car dynamo

The vehicle needs a current source to start the engine at the beginning of the rotation and after the rotation, the battery at the beginning of the rotation provides the electrical current necessary to start the engine rotation, but the battery is a storehouse of electrical energy and needs to be recharged after it is consumed.

As well as the large number of electrical devices that depend on electricity, it was necessary to provide a means that secures the current continuously during the rotation of the motor.

Therefore, a special device called the "generator" charging circuit was found, which recharges the battery and also supplies the electric current to various electrical devices according to the different operating conditions of vehicle driving.

Definition of Generator

A generator is a machine that converts mechanical energy into electrical energy by magnetic induction (generating coils for a magnetic field) according to Faraday's theory.

Farad's theory

That is, if a conductor cuts a magnetic field, an electromotive force is generated in this conductor, and the direction of the current can be determined by Fleming's right-hand rule.

Fleming right-hand rule

If the fingers of the right hand (thumb, forefinger, and middle) are made perpendicular to each other, and the thumb points to the direction of movement of the conductor and the index finger points to the direction of the magnetic lines, then the middle one points to the direction of the current inferred by the conductor.

Dynamo function in the car

Generator functions

Supplying all electrical devices in the car with the necessary current to operate them.

Charging the battery with a constant voltage (while the engine is running) when the electrical appliances are fully loaded.

Charging the battery at low speeds.

By converting the kinetic energy that it derives from the motor through the pulley into an electric current.

The generator must have the following characteristics:

Withstand stresses, shocks, and vibrations.

Small size.

Easy maintenance.

Types of alternators in the car

The electric generators used in cars are divided into two types

DC generators (which are like the electric current from a battery)

Alternating current generators (which is similar to the electrical current in homes)

DC generators

They are sometimes called "conventional DC generators", as the use of a lead-acid battery led to the development of this type of generator. This type of generator continued to work for a long time in vehicles, was able to meet the requirements for which it was used, and remained Existing within the charging system in vehicles until its presence has now disappeared. The performance of DC generators was linked to the presence of some defects, which led to their development and replacement by alternating current generators.

alternating current generators

In the recent period, there has been an increase in the requirements of electrical and electronic systems and circuits in modern vehicles of the electrical energy needed to operate them, and frequent, arduous and sometimes adverse changes in driving conditions have occurred.

Together, these conditions led to severe requirements for the charging system, and only the design of alternating current generators or the so-called "three-phase generator" was able to meet them, and its production was launched on the market in 1963 AD.

The name of the alternating current generator was shortened to (Alternator), which is a merged word from the two words “alternating current” and “alternator”.

Advantages of alternating current generators over direct current generators

Alternators were installed on the vehicle because of their design advantages over DC generators. Variable current generators are distinguished from direct current generators as follows:

Less mass and smaller size for the same capacity.

Moving parts are few.

Generates power even at low speeds.

Less maintenance.

Longer service life is given.

Battery recharge speed.

The life of carbon brushes (dynamo charcoal) is longer due to the small current passing through them.

The generator can be rotated in both directions while observing the fan adjustment.

Relatively high rotational speeds are allowed due to the quality of the rotor design.

car dynamo components

Car dynamo (generator): its components, function, how it works, and types? (1)
car dynamo components

The defects that appeared in the performance of the DC generator led to thinking about its development and the search for an alternative that could avoid these defects and turn them into advantages. Research and development reached an alternator, or the so-called "three-phase alternator" or three-phase (Alternators).


Car dynamo (generator): its components, function, how it works, and types? (2)

It is a moving part and it consists of clawed electrodes mounted on the generator shaft and coiled inside the excitation coils. These coils control the density of the magnetic lines and are among the factors affecting the generated current. These coils are fed by carbon brushes, where one is negative and the other is positive, from the current coming from the regulator, which controls the current according to the rotational speed and according to the current produced in the generator.


Car dynamo (generator): its components, function, how it works, and types? (3)


It is a non-rotating stator made of thin strips of coated steel to increase magnetic conductivity and overcome cyclonic currents. It also contains three conclusion coils connected in the form of a star or delta or, depending on the manufacturer, wrapped on the stator. The variable current that goes to the diodes is generated in it to convert it from alternating current to direct current.

Diodes (unifiers/silicons)

As is well known, diodes allow current to pass in one direction only. And because the deduction coils produce an alternating current that cannot be used to charge the battery or operate various electrical devices, so diodes were installed, where there are six diodes in the generator, three of which are on each coil one positive and three negative connected with the deduction files so that one negative.

All of them are placed on a holder, and this holder dissipates the heat generated by the diodes while adjusting the current.

Carbon brushes (dynamo charcoal)

Car dynamo (generator): its components, function, how it works, and types? (4)

Carbon brushes (dynamo charcoal)

Ces balais sont en carbone pour résister aux frottements et aux hautes températures, et ils ont la capacité de conduire le courant électrique. Il y a deux balais, l'un positif et l'autre négatif, car ils transfèrent le courant du régulateur aux bobines d'excitation en mettant en contact les balais de charbon avec les anneaux de cuivre à surface douce.


Les points de connexion dans les groupes électrogènes diffèrent d'une entreprise à l'autre en termes de nombre, par exemple :

Le générateur allemand a quatre points

Le né américain a trois points

Le générateur japonais a six points

Fan, pulley, belt, and grenade bearings for the generator

Car dynamo (generator): its components, function, how it works, and types? (5)

Roulements de ventilateur, de poulie, de courroie et de grenade pour le générateur

The pulley and the fan are installed on the generator shaft, which takes its movement from the engine through the generator belt. The fan cools the parts of the generator by pushing air into the generator so that it will not be damaged as a result of the high temperature resulting from friction between the parts. The fan may be internal or external, forming on the rotating member. As for the generator, its specifications differ from one car to another according to the design of the vehicle and generator manufacturer. As for the pomegranate bearing, it facilitates the movement of the rotating parts. And there are pomegranates in the generator, front and back.

generator body

The body of the generator is usually made of aluminum or its alloys, and it includes the various parts of the generator inside it.

charging lamp

It works to determine the validity of the generator for work and the charging lamp works on the battery voltage. As for its capacity, it is low. The lamp is lit when the vehicle’s ignition switch is opened and continues to light until the generator begins the process of generating current, after which the lamp turns off as evidence that the generator is in good condition. The terminals of the charging lamp are connected to the battery through the operating switch and the terminal The other is a connector between the alternator and charge regulator.


The generator derives its movement from the engine, which rotates at variable speeds. Therefore, the voltage (volts), the intensity of the current (amps) and the power generated are constantly changing, and the amount of current drawn during the night is different from that during the day and in the summer from the winter, and in addition to that, the state of charging the battery is variable Therefore, the generator must give a constant voltage, despite the change in the speed of rotation of the motor, so the generators are provided with a regulation group that regulates this process, and there are many types of regulators, but they are in agreement in their essence, some of which are installed inside or outside the generator of the electromagnetic or electronic type.

How does a car dynamo work?

When the vehicle's ignition switch is opened, the current comes from the battery to the lamp, and it lights up (this indicates that there is no charging process) and then to the charging regulator, where the units do not allow it to enter the generator, but the current flows to the generator through the charging regulator to the rotating member through the carbon brushes and completes its flow to Negative line.

When the generator rotates after the engine rotates, a current is produced in the conclusion member as a result of the rotation of the rotating member and cutting the magnetic field lines. This current is an alternating current, and the current flows through the units that convert the alternating current into a direct current capable of charging the battery.

Condition The lamp is extinguished due to the negative line being cut off from the lamp circuit, which is evidence that the generator has started the charging process. When the engine speed increases, the battery is fully charged and the current generated inside the generator increases, so the regulator then organizes and adjusts the charging process according to the operating conditions of the vehicle.

And due to the different operating and driving conditions of the vehicle, there are multiple cases of the alternator charging stages of the vehicle’s battery, which are as follows:

First, the amount of voltage is less than the charging rate

This condition occurs when the vehicle is running and the generator voltage is less than the battery voltage, so a current flows from the battery through the charging lamp, which lights up as an indication that the generator has not reached the charging rate, and the electric current cycles by passing through the contact points to the coil and then to the alarm coils through the point (DF) and then It completes its cycle to the negative (ground) line. In this case, it is not possible to pass an electric current from the battery to the conclusion member in the generator, as the units prevent its passage. (The unit allows the current to pass in one direction only).

Secondly, the amount of voltage is equal to the charging voltage

This case occurs at a slow speed, where the voltage is equal to the charging rate, so the current flows from the generator through the units to the positive battery, and the alarm coils are fed through the (+D) terminal to the contact points and then to (DF). It is noted that there are three groups of units, two groups of which charge the battery and the third group is for alarm current.

Third: The voltage of the generator is slightly higher than the voltage of the battery:

This situation occurs at the average speed of the vehicle, so the generator voltage exceeds the charging voltage, so the current passing through the units works to the end (+D) and then to the regulator core (coil), so the magnetism works to pull the core that pushes the regulator vane and puts it in the middle between the contact points, so a current is forced The alarm passes through the resistance to (DF) to the positive of the alarm coils, so the resistance reduces the voltage of the alarm current, and thus the generator voltage decreases, and the vane remains oscillating to adjust the charging voltage.

Fourth: The voltage of the generator is much higher than the voltage of the battery:

This situation occurs at high speed, where the voltage of the generator increases a lot, then the magnetic field in the regulator core coil intensifies, which pulls the core more and pushes the vane until it comes into contact with the contact patterns connected to the negative of the generator (-D), so that the vane connection becomes negative, and thus the alarm coil of the rotor is under the influence Two negative contacts, so there is no current to alert.

This type of regulator is used in small passenger vehicles, and one of its most prominent defects is damage to the contact points, so it was replaced by electronic regulators made of semiconductor materials.

Car dynamo (generator): its components, function, how it works, and types? (6)
Car dynamo (generator): its components, function, how it works, and types? (2024)
Top Articles
Latest Posts
Article information

Author: Mrs. Angelic Larkin

Last Updated:

Views: 5704

Rating: 4.7 / 5 (47 voted)

Reviews: 86% of readers found this page helpful

Author information

Name: Mrs. Angelic Larkin

Birthday: 1992-06-28

Address: Apt. 413 8275 Mueller Overpass, South Magnolia, IA 99527-6023

Phone: +6824704719725

Job: District Real-Estate Facilitator

Hobby: Letterboxing, Vacation, Poi, Homebrewing, Mountain biking, Slacklining, Cabaret

Introduction: My name is Mrs. Angelic Larkin, I am a cute, charming, funny, determined, inexpensive, joyous, cheerful person who loves writing and wants to share my knowledge and understanding with you.