What is an Alternator? | How does Alternator work?

The battery is one of the most important parts of the vehicle. It runs the stator motor to start the vehicle engine. An alternator uses to charge the battery. The alternator takes mechanical power from the engine and transforms it into electrical power to charge the battery. This article mainly explains the working, function, and parts of the car alternator.

What is an Alternator?

An alternator is an electrical generator that transforms mechanical power into electrical power in the form of AC (alternating current).

The alternator uses a rectifier to transform the output alternating current into a direct current. The resulted DC is used to charge the battery of the vehicle.

alternator

The alternators are most commonly used in the latest vehicle models.  

In vehicles, the engine shaft connects to the pulley via a drive belt. The pulley further connects to the alternator. As the engine shaft rotates, it turns the pulley which further turns the shaft of the alternator.

When the shaft or rotor of the alternator turns, it produces alternating current (AC). The rectifier further converts AC into DC and transfers output DC power to the battery. The battery further uses this DC to run the starter power.

The alternator is located at the engine front and is run by the engine crankshaft. The alternators are available in different designs.

The magneto alternator is one of the most famous alternators. It is equipped with a permanent magnet for the magnetic field. However, the main function of the alternator in all mechanical applications is to charge the electrical units of the system.

Therefore, alternators are used in nuclear power plants, hydel power plants, and thermal power plants to convert mechanical power into electrical power to deliver electricity to the power system.

Functions of Alternator

The alternators take mechanical energy from the engine and convert it into electrical energy to charge the battery. An alternator performs the below-given functions:

  1. The main function of the alternator is to charge the vehicle battery. The battery power further uses to run the starter and other electrical parts in the vehicle.
  2. When the vehicle is in motion, the alternators produce energy to power the electrical systems and battery.

The alternators work in the same way as generators. When the engine turns the shaft of the alternator, it produces AC (alternating current) which further converts into (direct current).

Working Principle of Alternator

The working of the car alternator is very simple and easy to understand.

Working of alternator

The alternator has two windings, i.e., a rotor and a stator. The rotor rotates inside the winding while the stator remains stationary outside the winding.

As the voltage regulator delivers voltage to the rotor winding, it starts rotating in a magnet.

The car engine shaft connects to the pulley via a drive belt. The pulley further connects to the alternator. As the engine shaft rotates, it turns the pulley which further turns the shaft of the alternator.

When the shaft or rotor of the alternator turns, it produces alternating current (AC). The rectifier further converts AC into DC and transfers resulted DC power to the battery. The battery further uses this DC to run the starter power.

Read More: Working and types of AC Generator

Types of Alternators

The alternator has the following major types:

1) Types based on alternator use

  • Marine alternators: They commonly use in marine applications.
  • Automotive alternators: These types of alternators are usually used in the latest vehicles.
  • Radio alternators: They use to transfer low band radio frequency transmission.
  • Brushless alternators: They use in electricity production powerplants as the major source of power.
  • Diesel-electric locomotive alternators: These types use in diesel-electric multiple devices.

2) Types Based on alternator Design

  1. Salient pole rotor
  2. Smooth cylindrical Rotor

1) Smooth Cylindrical Generators

The smooth-cylindrical generator is designed for alternators driven by steam turbines. The rotor of this generator consists of a solid, smooth-forged steel cylinder with a specific number of slots designed to house the field coils.

These rotors have a very high rotating speed. This rotor is designed for a 2 or 4-pole turbine generator rotating at 36000 rpm or 1800 rpm, respectively.

2) Salient Pole Types

The salient pole alternator uses as a low to medium-speed alternator. These alternators have a large number of salient poles, the core of which is bolted to a heavy magnetic wheel. Magnet wheels are made of steel or cast iron with excellent magnetic properties.

Components of the Alternator

The alternator has the following components:

  1. Regulator
  2. Rectifier
  3. Rotor
  4. Slip Rings
  5. Slip Ring End Bearing
  6. Stator
  7. Drive End Bearing
  8. Pulley

Alternator Components

1) Regulator

A voltage regulator uses to control the current flow from the alternator to the battery. It also handles the charging process of the battery. This part performs a different function according to the nature of the application.

2) Rectifier

When the engine turns the alternator, it produces alternating current. However, a car battery needs a direct current (DC) to be charged. The rectifier converts the AC into DC and charges the battery.

3) Rotor

The rotor is one of the most important parts of the alternator. It contains multiple blades. It rotates and turns the pulleys and driving belt system. The rotor works like a rotating electromagnet.

4) Slip Rings

The slip ring is a method of generating DC (direct current) and powering the rotor.

5) Slip Ring End Bearing

These types of bearings are intended to rotate the rotor shaft.

6) Stator

It is an iron ring around which multiple coils are wound. Some portion of the stator acts as the housing of the alternator. It generates an electric current when the magnetic field is generated.

7) Drive End Bearing

The drive end bearing also assists in rotating the rotor shaft.

8) Pulley

It connects to the drive belt system and rotor shaft. When the engine crankshaft rotates, the drive belt takes rotation by the engine and transfers it to the pulley.

The rotation of the pulley plays a big role in generating the electric current, which further uses to charge the battery.

Symptoms of a Bad Alternator

The alternator plays a big role in the efficient working of the vehicle. As the alternator goes bad, it doesn’t properly charge the vehicle battery due to that vehicle engine doesn’t start.

A bad or faulty alternator produces one of the below-given signs:

  1. Burning rubber or Wires smell
  2. Overly or Dim bright Light
  3. Whining or Growling Noises
  4. Dead Battery
  5. Frequent Stalling or Trouble Starting
  6. Malfunctioning or Slow Accessories
1) Overly or Dim bright Light

As the alternator goes bad, it doesn’t supply voltage to the electrical parts of the battery or supplies inconsistent voltage. This often manifests the under-performing or over-performing devices, e.g., headlights that are either too weak or too bright.

The blinking light or lights that change unsteadily from dark to light and vice versa is also a sign of bad alternators.

2) Dead Battery

A dead battery is one of the most common signs of a bad alternator. The battery has a specific service life. As it dies, it doesn’t work and doesn’t supply current to the electrical parts of the vehicle.  

During the operation of the engine, a faulty alternator cannot fully charge the battery and drains it faster than normal. One of the best methods to check if the problem is with the alternator or the battery is to jumpstart the vehicle.

3) Malfunctioning or Slow Accessories

The faulty alternators damage the electrical accessories of the vehicle. When the alternator doesn’t provide sufficient power to the battery and other electrical components of the vehicle, then they will ultimately slow down or fail.

For example, when you observe that the window rolls up and down process takes more time than usual, warmers feel “off,” the speedometer or other gauge starts to lose control, then there may be a problem with the alternator.

4) Frequent Stalling or Trouble Starting

As mentioned above, the inability to start the engine might mean that the alternator is not producing enough power to charge the battery. This means that as you turn the ignition key, you will hear a clicking noise, not the roar of the engine.

However, if the vehicle stalls regularly while driving, this may indicate that the spark plug is not receiving adequate current from the alternator to continue the engine operation.

However, the vehicle may start stalling due to many other reasons, such as a bad spark plug, bad head gasket, damaged cylinder block, or low coolant.

5) Whining or Growling Noises

The whining noise is a sign of bad alternators. As the alternator goes bad, your vehicle may start generating growling noise from under the hood.

This whining noise occurs as the belt that spins the alternator pulley is misaligned or rubbing against the pulley sides. In such a condition, you must immediately contact a specialist to fix the problem. If you ignore the issue, it may lead to expansive repair.

6) Burning rubber or wires smell

An unpleasant smell of burnt rubber or wire may indicate that some components of the alternator have been worn out.

When the vehicle alternator is overloaded or cords are damaged or frayed, it may generate a burning smell like an electrical fire. The overloaded alternator attempts to transfer excess power through the cords due to that the cords heat up in an unsafe state.

Alternator vs Generator

The main differences between the alternator and generator are given below:

GeneratorAlternator
A generator is a machine that converts the mechanical energy of the main engine into a direct current or alternating current.An alternator is a machine that converts the mechanical electricity of the main engine into AC power.
The output power of the generator is not much stronger than the alternator’s output power.The output power is more than the generator output power.
It has the ability to produce either direct current or alternating current.It can only produce AC.
It contains a rotating magnetic field to produce a low-voltage, constant, and high-voltage magnetic field.It contains a spinning magnetic field.
The generator has the ability to charge a fully dead battery.It can’t charge a fully dead battery.
The generator output voltage remains constant.The output voltage of the alternators is variable.
It is less efficient.It is more efficient than the generator.
Generators must be polarized after installation.It doesn’t need polarization.

FAQ Section

Where Is the Alternator located in a Car?

The alternator is located in front of the engine and is driven by the driven belt of the engine. It connects to the engine crankshaft. When the crankshaft rotates, it transfers rotation to the alternator.

When the alternator receives power from the crankshaft, it moves magnets on a special surface cable and wired known as the conductor.

How do you tell if it’s your battery or your alternator?

If the car battery is not charging, it means that there is a problem with the battery or the alternator. If your vehicle battery dies immediately after starting the vehicle, it means you have a bad alternator. If the battery is charged but can’t start the car, there is a problem with your battery.

What does an alternator do?

An alternator takes mechanical power from the vehicle engine and converts it into electrical power in the form of AC (alternating current). The alternator uses a rectifier to transform the output AC power into DC power. The resulting DC power is used to charge the battery of the vehicle.

How to reduce the eddy current losses??

You can decrease the eddy current losses by laminating the core and insulating it from each other with the help of a varnish or a paper.

What are the signs of a bad alternator?

Following are the common signs of a bad alternator:

  1. Burning rubber or Wires smell
  2. Overly or Dim bright Light
  3. Whining or Growling Noises
  4. Dead Battery
  5. Frequent Stalling or Trouble Starting
  6. Malfunctioning or Slow Accessories

How much does it cost to get the alternator replaced?

The replacement process of the alternator usually takes two to three hours. The replacement cost of the alternator varies according to the labor cost, vehicle model, and the type of brand. If you use OEM parts, you can expect to pay from $190 to $360 for a new alternator.

How long does it take to replace an alternator?

In general, it will take about two hours for you to replace an alternator on your own, though this could vary somewhat depending on your knowledge of car mechanics. If you take your car into a shop in order to have the alternator replaced, the timing may vary somewhat, and you may have to leave the car for the day.

Can you drive a car with a bad alternator?

Technically yes. If you have a bad alternator or you’re just starting to experience car alternator problems, you can still drive it; however, it’s best not to. If your alternator has stopped working entirely, you have minimal time before your car stalls and won’t restart since you have a dead battery.

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