Alternator parts and function

The alternator is a main part of the charging system. The alternator produces electrical energy while the engine is running to charge the battery. When the engine is off, the battery can be used as an electrical power source to power the starter motor and make the engine runs.

There are two main functions of the alternator to the charging system. The first is to generate electrical power to run all of the car's electrical systems. The second is to generate currents to recharge the car battery.

A certified technician can repair most alternators because alternator parts can be replaced separately; even carmakers recommend replacing them as an assembly. This article will give you information on alternator parts and functions to understand why we can replace those parts.

1. Pulley

The first alternator part is a pulley. The pulley function is to rotate the rotor assembly as the engine is running. Yes, the pulley works as a connector between the rotor assembly and the engine through a drive belt were known as an alternator belt or serpentine belt.

There are three types of alternator pulleys, solid pulleys, one-way clutch pulleys (OWCs), and overrunning alternator decoupler pulleys (OADs). Even though they have different types, the function remains the same; rotating the rotor assembly as the engine runs.

2. Housing

The second alternator part is housing. The housing function is to protect the inner parts of an alternator and become a household of them like stator, bearings, rectifier, etc.

The housings are split into two parts, front housing, and rear housing. Front housing is located near the pulley, while the rear housing is at the opposite. Between them, there is a stator assembly body.

3. Bearings

The third alternator part is the bearings. The bearings function is to make the rotor assembly rotate freely. They are attached in front of and at the end of the rotor shaft. They support the rotor shaft, so the rotation runs smooth and freely.

These bearings sit on the alternator housing. The front bearing is attached to the front housing, and the rear bearing is attached to the rear housing.

4. Rotor assembly

The fourth alternator part is rotor assembly. The rotor assembly function generates a magnetic field by electromagnetic force built up because the electric current flows from the battery through the rotor coil.

When the rotor assembly is spinning, the magnetic field will cut the stator coil. As the magnetic field cuts the stator coil, the stator coil generates electrical energy. The faster the rotor rotations, it's increasing the electric current induced in the stator coil.

The rotor assembly is built from several parts, such as

Rotor shaft; the shaft that will rotate the rotor assembly. It is connected to the bearings and on the rear end shaft.
North claw poles; the north claw poles changed to be the north pole electromagnetic when the electric flow through the rotor coil.
South claw poles; the south claw poles changed to be the south pole electromagnetic when the electric flow through the rotor coil.
Rotor coil; A coil rolled between the rotor shaft and the rotor claws (north and south claws). This coil is connected to the slip rings.
Slip rings; rounded shapes cooper were connected to the rotor coil. The slip rings make the electric current flows while the rotor shaft is spinning.
Cooling fan; the cooling fan function is to cool down the air temperature inside the alternator.

5. Stator assembly

The fifth alternator part is stator assembly. The stator is a stationary set of windings that surrounds the rotor. The stator assembly function generates electric current as the rotor assembly (being electromagnetic) cuts the stator coil. The coil builds in rounded shapes so the rotor assembly can rotate inside the stator coil.

Two types of coil connections were used inside the stator coil, Y connection, and delta connection. In a Y connection type stator, the wire ends from the stator windings are connected to a neutral junction. The circuit looks like the letter "Y." A Y-type stator provides a good current output at low engine speeds.

In a delta connection type stator, the wires are connected end-to-end so that the circuit looks like a triangle. Delta-type stators are used in high-output alternators.

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6. Rectifier

The sixth alternator part is a rectifier. The rectifier converts current from alternating current (AC) to direct current (DC) during the charging process.

Since the stator windings generate an alternating current, they cannot be used in most car electrical systems. So, to convert the alternating current to be direct current, an alternator is equipped with a rectifier built from 6 or more diodes.

7. Voltage regulator

The next alternator part is the voltage regulator. The voltage regulator controls the amount of power distributed from the alternator to the battery to control the charging process. As we mentioned before, "more faster the rotor rotations, it's increasing the electric current were generate in stator coil," so the voltage regulator is used to control the output voltage.

Suppose the alternator output voltage is below 14.5 volts. In that case, the voltage regulator responds by increasing current through the field coil of the rotor. It causes the voltage to increase. And suppose the alternator output voltage is at or above 14.5 volts. In that case, the voltage regulator will decrease the current through the field coil of the rotor, so it causes the output voltage to decrease.

Today's modern cars use an IC regulator type attached inside the alternator and built-in with a carbon brush connected with the rotor assembly slip rings. In contrast, the olds used an external voltage regulator.

8. Protective cap

The last alternator part is the protective cap. The protective cap is used to protect the rectifier components were placed outside of the rear housing. This protective cap is dependent on the alternator makers. Some makers did not use a protective cap. Still, they put all parts inside the alternator and just leaving the terminal +B and socket.