Things you need to know about alternator

Most vehicle users never understand the secret behind self-charging automobiles, well, you’ll get to know about alternators here. You should know battery can get faulty, but alternator should be asked when it gets low. It’s a charging system that boosts the engine battery power.

Alternators are found are front of the engine, driven by the crankshaft. there are different types and designs. The one’s with permanent magnet for a magnetic field is known as magneto while alternators in power stations driven by steam turbines are called turbo-alternators. Nevertheless, the primary function of alternators in any mechanical application is for charging their electrical devices.

what is alternaltor

Early vehicles use separate drive belt to drive the alternator’s pulley. But in modern cars, a serpentine belt or one belt drives all components using the crankshaft power. Most alternators are installed using a bracket that bolts a specific point to the engine. One of the brackets is in a fixed position, while the other is adjustable so that the drive belt can be properly tightened.

Today we’ll be looking at the definition, functions, parts, diagram, types, working principles, and worse symptoms of an alternator used in an automotive engine.

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Alternator Definition

An alternator can be defined as an electrical generator that converts mechanical energy into electrical energy. The work is done in the form of an alternating current. The electrical components consist of a rotating magnetic field with a stationary armature, making it design less complex and cheap.

An automotive charging system consists of three major parts that include batter, voltage regulator and alternator. Without any, these three, charging system is incomplete, though alternators now carry voltage regulators. The alternator works with the battery to generate power the electrical components of the vehicle like the interior and exterior lights, etc.

Well, alternators get their names from the term alternating current (AC) as they produce power through electromagnetism. This electromagnetism is formed through the stator and rotor relationship. This will further have explained below this article.

Functions of Alternators

Below are the functions of alternators

  • The primary function of an alternator is to charge a car battery so that other electrical components in the car can be powered.
  • The charged battery provides the electricity needed for the starter motor to start the car. And
  • When the car is running, alternators generate energy to feed the electrical system and the battery.

Alternators function as generators as they work the same ways. The pulley turns and creates direct current (DC). During the rotation, an alternating current (AC) passes through a magnetic field that creates the electrical current.

Major Components of an Alternator

Below are the components of an alternator and their functions:


The voltage regulator is a part that controls the amount of power supply from the alternator to the battery. It controls the charging process as it’s designed with various functions and work depending on their applications.


The rectifier is used to convert alternating current (DC) produce to direct current (DC) during the charging process.


The rotor is a part that spins inside the alternator and rotates the pulley and drives belt system along. It acts as a spinning electromagnet.

Slip Rings:

The slip rings are a means of obtaining direct current and offering power to the rotor.

Slip Ring End Bearing:

Alternator bearings are designed to support the rotation of the rotor shaft.


A stator is an iron ring that contains several coils of wire wound around it. the part of the stator serves as the body of the alternator, creating an electrical current when a magnetic field is made.

Drive End Bearing:

The drive end bearings also help to support the rotation of the rotor shaft.


The pulley is a part connected to the rotor shaft and the drive belt system. Though the rotation is obtained from the engine transferred by the drive belt to the pulley. The rotation causes the charging process.

Alternators contain some functional tiny components in them, though we’ve explained few essential. but inside the electrical device, we can find a diode rectifier or rectifier bridge, voltage regulator, slip rings and brushes. We can also find the rotor field winding, finger poles, field winding, stator, etc.

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There are several terminals or connecting point at the back of an alternator serving various purposes:

IG Terminal – is the ignition switch that turns on the voltage regulator.

S Terminal – is a connecting point that senses battery voltage.

L Terminal – it closes the circuit to the warning lamp.

B Terminal – is the main alternator output terminal. It’s connected directly to the battery.

F Terminal – is a full-field bypass for a regulator.

diagram of a car alternator

Types of Alternators

Alternators are classified in many ways depending on their designs and applications. Below are the 5 types of alternators based on their applications:

Automotive Alternators – are found in modern automobiles.

Diesel-electric Locomotive Alternators – used in diesel-electric multiple units.

Radio Alternators – used for low band radio frequency transmission.

Marine Alternators – used in marine applications

Brushless Alternators – used as the main source of power in electrical power generation plants.

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AC generators (alternators) are also categorized base on design:

Smooth Cylindrical Generators:

The smooth cylindrical types of generators design as used for a steam turbine driven alternator. The rotor is made of smooth solid forged steel cylinder designed with a certain number of slots milled out to accommodate field coils. It rotates at a very high speed, as it can contain 2 to 4 poles turbo generator, running at 36000 rpm or 1800rpm respectively.

Salient Pole Types:

These types of alternators are used as a medium and low-speed alternator. It contains a large number of projecting poles with their cores bolted onto a heavy magnetic wheel. The magnetic wheel is of cast iron or steel of good magnetic quality. These generators look like a big wheel but are mainly used for low-speed turbine such as in hydel power plant. But they are categorized by their large diameters and short axial lengths.

Working Principle

The working of AC car alternator is quite simple and less complex. It contains two windings such as a stator (stationary outside winding) and a rotor (rotating inner winding). The voltage regulator supplied voltage to the rotor winding which energizes and turns it into a magnet. Via a pulley, the rotor is rotated by the engine through a drive belt.

As the magnetic field is produced by the rotating rotor, it induces AC electric current in the stationary stator winding. The diodes help to convert the AC current into DC current the vehicle’s electrical system requires. Generally, voltage regulators are built-in in the alternator. They controlled the out voltage.

Automobile alternators are relatively small and lightweight, constructed with an aluminium outer housing. this light metal does not magnetize, which is why dissipates heat produce during the process and because the rotor assembly produces a magnetic field. There is a vent on both the front and back of the alternator, it also helps in the heat dissipation.

As the engine is running, the crankshaft turns the drive belt that spins the alternator pulley. And as the alternator rotates the current is produced. This is why it’s said that alternators transfer the engine’s mechanical energy of the engine into electrical power for the car components.

Water video of alternators working:

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Symptoms of Bad and Failing Alternator

Below are common symptoms of a bad and failing alternator:

One of the most common symptoms that often occur in a vehicle charging system is the battery icon warming light in the dashboard will be on while driving. Conventionally, the warning light will be on when the car ignition is on but will off as soon as the engine is started. Staying on indicates there is an issue with your engine charging system. A professional need to examine the engine, since the warning light does not directly say the alternator is the problem. But alternator is the common problem for such a sign.

In a weak charging system, you will see the dashboard lights and headlights dim at idle but become brighter when the engine is revved. This issue can be caused by a weak alternator, failing battery, poor battery connection or loose serpentine belt. A buzzing or whining sound from the alternator is another symptom of failing alternators. This could be caused by a faulty bearing inside the alternator.

Most common alternator problem include worn contact rings, worn carbon brushes, or a failing voltage regulator. Rebuilding the alternator, the bearings, voltage regulator, brushes and some smaller should are typically replaced with new ones.

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In conclusion, alternators are a great component in the automotive charging system. We saw it functions, parts, working. We’ve also seen its types and some bad signs or symptoms of a failing alternator.

I hope you enjoyed the reading, if so, kindly comment, share, and read some other post to gain more knowledge. Thanks!

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