How Does an Alternator Work ?

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Working Principle of Altenator - charging system serves to generate electrical energy to supply all the electrical needs of the vehicle. This system uses a component called "Altenator" to produce electricity. Then, how does the altenator work?

The principle of altenator is same with a generator that generates home electricity. But the difference, this altenator will generate AC power. The altenator generate electricity by changing the rotary movement (kinetic) to electrical energy.

How does the Altenator Working Principle?


As we mentioned above, the altenator works by converting energy from motion (kinetic) to electrical energy. This process uses electromagnetic force.

The altenator uses Faraday's law which states that if a conductor in the middle of a varying magnetic field and bypassing the magnetic force's line, an electric force will be formed at the end of the conductor.

In other words, the electricity is obtained from the intersection of the magnetic force lines between the two components, hereinafter called the Stator (conductor) and Rotor (the provider of magnetic field).

In an altenator there are three main components

1. Stator Coil

The stator is a static coil, the coil is located around the rotor coil. Its function as the conductor that will keep the electron field from the rotor when the magnetic force intersects. This stator has two ends as the source of current and current output.

2. Rotor Coil

The rotor is a rotating coil (spinning). The function is as a provider of the magnetic field and intersects the magnetic force line. The rotor coil will be connected to altenator pulley. When the engine is on, The pulley spin, and the result is a electricity movement in the stator coil.

3. Diode Bridge

The diode bridges are ranges of diodes arranged in several phases to create a one way curent (DC). The altenator produces AC current while the vehicle needs DC current, and it is this component that is responsible for rectifying the current.

How does an altenator work?


When the ignition key is ON then the electricity from the battery will flow to the rotor coil and there is magnetism around the rotor coil. (the position of the coil rotor is inside the stator coil).

When the engine cranking, then the engine pulley will rotate. The pulley rotation of the engine will rotate the altenator pulley, consequently the rotor coil that connected to the altenator pulley will also spin. The rotation of the coil rotor causes the intersection of the magnetic force line because previously the magnetic field has been generated when the ignition key is ON, so that when there is movement of the rotor, then the flow of electricity will be generated.

The amount of electric voltage that is present in the stator coil is influenced by the RPM rotor. If the RPM of the rotor is low, then the resulting electric voltage will also be low. But, when the RPM is high, then the voltage will also be high.

The Diagram of magnetic lines intesection

Visible clearly, when the rotor coil rotates the rotor poles will vary every 180 degrees of rotation. This is what causes the resulting current is AC (Alternate Curent)

The output of the stator coil is two, ie ground and B +.  The ground output will be directly connected to the car body, while the B + ouput from the stator will be connected directly to the diode bridge for rectification. The rectification process will be done automatically because the diode does have a function to block the current from one direction. So that, when the curent passing the diodes, the curent is only passing in a direction (tipicaly DC).

In an altenator there are at least 3 terminals, namely the F and N terminals used to adjust the rotor voltage. And the B terminal is connected directly to the starter and battery main cable.

The electricity that has passed through the diode bridge, is DC but can not be used directly. This is because the car's electricity is only resistant to a maximum 14 Volts. While the altenator can produce more if the RPM is high. So there needs to be additional components named regulator.