Alternator Parts Name and Their Functions

Almost all praise goes to the battery when a car starts. The battery typically helps start the engine and supplies the power needed to operate a car’s electronics even when the car is off. However, the battery needs enough charge to do this, which can only be provided by the alternator. The alternator, often called an electrical generator, helps convert mechanical energy to electrical energy and uses this energy to charge the battery and power car appliances while the car is in motion.

The alternator, however, comprises different components to help carry out its function effectively. So in this article, we will discuss alternator parts name and their functions. But first, let’s look at the different types of alternators out there.

types of alternator

Types of alternator

While an alternator serves the same purpose, it comes useful in different fields. Hence, diverse alternator types. So there are different types of alternator out there.

Automotive alternator

These alternators are used in vehicles to charge a vehicle’s battery and power its electrical accessories. The alternator can, however, do this only when the engine is running.

Because the alternator supplied enough power, even when the car has stopped, the battery will still have some charge to start your car again and power the accessories. A non-functioning car alternator will surely cause battery problems.

Marine alternators

Marine alternators are used in marine applications such as boats, yachts, etc. These types of alternators are built to adjust well to salty water environments. They are also explosion-proof, so they won’t cause sparks that can ignite the air-fuel mixture in the equipment compartment. The bigger the marine application, the more likely they would use two or more alternators.

Diesel-electric alternators

These types of alternators are used by diesel electrically operated trains. Here, the diesel engine turns on the alternator, which supplies electricity to the traction motor to power the train. However, while this type of alternator helps in powering trains, the traction motor can also be used in moving hybrid and pure electric passenger cars.

Radio alternators

This type of alternator was very rampant in the days of radio transmission.

They are used for transmitting frequency in low-band radio and are very useful in communication over a long distance. Back in the day, these alternators were costly to build; however, they soon became irrelevant as vacuum tube transmitters were introduced by the end of world war-1.

Brushless alternators

Brushless alternators are used to generate electrical power in power plants. The alternator is connected to the grid, which invariably supplies the electricity. These types of alternators come in handy as the main power sources for commercial and residential buildings.

Parts of an alternator

The alternator consists of many components to ensure it works as intended.  So here are some of the major parts of an alternator and its functions.

car alternator parts


The rotors are a group of magnets inside the alternator. They are driven with the help of a belt and are responsible for generating a magnetic field inside the copper wiring. The alternator rotor function by rotating at a constant speed with the help of a connected pulley to create this magnetic field.


The stator is an iron ring that has special wire coils wound around it. This component is responsible for creating an electrical current called (alternating current) when magnetic fields are made. It works directly with the rotor shaft.

Diode assembly (rectifier)

Batteries and car accessories work on a current called DC (direct current). However, the current generated by the stator is called alternating current(AC), which batteries can’t use. This is where the diode assembly comes in handy. The diode assembly helps convert alternating current to direct current so the battery or car accessories can use it.

Voltage regulator

It’s been explained that the alternator supplies the battery with an electric current to keep it working. However, this supply needs to be moderate, hence the voltage regulator.

The voltage regulator regulates the current supplied from the alternator to the battery. This way, the battery gets just the right amount of energy needed. So typically, the voltage regulator controls the charging process.

Slip ring

The slip ring serves as a medium of getting direct current and also comes in handy in supplying the rotor power.

Slip ring end bearing

An alternator consists of several bearings, one of which is the slip ring end bearing. It helps in providing support for the rotation of the rotor shaft.

Drive end bearing

The drive end bearing, like the slip end bearing, also helps to support the rotor shaft rotation.


The brushes help transmit electric current to the rotor field or wiring field. From where the magnetic field is created, invariably generating an alternating current.


The pulley is attached to the rotor shaft and drives belt system and typically helps in the rotation that causes the charging process. Power is typically transferred from the drive belt to the pulley to start the rotation that starts the charging process.

parts of an alternator and their functions


Q: What are the three main parts of an alternator?

The alternator no doubt comprises different parts that help it function optimally.  There are, however, some very important ones. So what are the main parts of an alternator? The three main parts of an alternator are the rotor, stator, and diode.

While the rotor constantly rotates to build a magnetic field, the stator helps create the alternating current. The diode, on the other hand, helps convert the alternating current to direct current for the battery and car accessories.

Q: What is an alternator assembly?

An alternator assembly is everything that makes up an alternator. This includes both the external and internal parts. Typically, the parts that work to produce the current and others that seal the alternator. This may include the plastic cover, regulator, rectifier, S.R.E bracket, bearing, bearing cap, terminals, wirings, stator, D.E bracket, rotor, pulley, and pulley cap.

In some modern alternators, a cooling fan helps keep the alternator cool. So when we talk of an alternator assembly, we talk about everything put together to make it function as an alternator— generating the power needed to run applications.

Q: Is an alternator AC or DC?

An alternator is AC. The alternator’s rotor, through constant rotation, generates a magnetic field that invariably helps the stator generate electric current. This current it generates is known as an alternating current.

However, because batteries and car accessories work on DC (direct current), the diode assembly helps to convert AC into DC for battery and car accessories to use.

Q: What are the 4 wires on an alternator

The four wires on an alternator work collectively to power the alternator and regulate its output to the battery. They include the main positive, main negative, field, and sense wires.

The main negative wire is connected to a car’s chassis and lowers the electrical interference, invariably enabling a good connection in the sense wires. The main positive wire is linked to the output port located behind the alternator; its job is to send electrical current from the alternator to the battery.

The sense wire is connected to the voltage regulator battery flank and helps the regulator detect the alternator’s voltage and uses this information to regulate the alternator output. Lastly, the field ignition input wire is connected to the ignition warning light and helps to notify drivers when the alternator isn’t functioning properly.

Q: What are the two main functions of an alternator?

The alternator first generates current by converting mechanical energy from the engine to electrical energy. Then supply this energy to charge your battery and power your car’s accessories. However, the alternator can only do this when the vehicle runs since it uses the engine’s mechanical energy to generate electricity.

So the longer you drive, the better charge your battery gets. However, when the car is parked, the battery powers your car’s accessories. If the alternator fails, and maybe you’re able to start the car, it won’t get long before the battery runs out of charge and stops. Hence, the importance of a functional alternator.


Alternator parts name are crucial to know how an alternator works. It typically consists of several parts to function optimally, the voltage regulator and three main parts that do most of the job.  This includes the rotor, stator, and diode assembly. Generally, the alternator helps charge the battery and provides electricity to run your car accessories when the car is in motion.

With the alternator out, it won’t be long before your battery runs out of charge and causes the car to stop. So it will be appropriate to diagnose what’s wrong with the alternator and fix it. Depending on the type of alternator and which component is faulty, alternator parts price could be anywhere between $3 and $70.


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