What is an Alternator? How does it Work?

The alternator is an electric generator that converts mechanical energy into electrical energy, particularly in the form of alternating current (AC). It is an essential component of almost all vehicles with an internal combustion engine.

The alternator also distributes the electricity to the vehicle and recharges the batteries. It is approximately the size of a coconut and mounted at the front of the engine.

The alternator keeps your car alive when you are driving. It powers the electronic components of cars such as electric steering, headlights, power windows, wipers, radio, and dashboard instruments. Moreover, the alternator also has applications in radio frequency transmission, electrical power generating plants, etc.

As the alternator is important for the charging system of cars, it is better to learn about its components and understand its operation if your car is not starting.

The alternator consists of many components which work together to provide the right amount of power to the vehicle. Construction of alternators may vary depending on the manufacturer, but every alternator contains these components:

The rotor is an electricity-producing component of the alternator. It consists of an electromagnet mounted on a shaft, which is basically a set of conductive copper wires wrapped around a magnetic metal. A magnetic field is created around the wires by applying a voltage to them. So, a rotor has a series of alternating north and south poles. Moreover, the rotor is rotated by a drive belt pulley system while the vehicle engine is running.

This is the stationary part of the alternator, which houses the rotor. Rotor safely spins inside the stator without touching it. The stator comprises three coil windings, uniformly spaced at intervals of 120 degrees around the shaft, with one end of each winding is joined together. The spinning of the rotor around stationary coil windings in the stator produces an induced voltage across the stator due to the rotating magnetic field.

As the name indicates, the Voltage regulator governs the energy produced by the alternator. It is a device that keeps an eye on the battery voltage level. The voltage regulator can be of different shapes and sizes. The main purpose of the voltage regulator is to adjust the electromagnet energizing voltage to keep the stator output voltages constant. This is essential because high voltage can damage the battery and other electrical devices.

The diode rectifier converts the produced AC voltage to DC. The rectifier has six diodes present on a heatsinking material to protect them from heating up. These diodes allow the current to flow in a single direction only. A diode consists of two terminals, cathode, and anode. The current will flow through the diode when the anode is more positive than the cathode. On the contrary, the current will not flow when the anode is more negative than the cathode. When AC voltage is applied to a circuit with diodes, we get DC voltage, and this conversion is called rectification.

The alternator can really heat up during its operation and needs to be cooled down for efficient working. They are built with vents and aluminum casing to dissipate the heat, but rotating fans are also installed to provide additional cooling. The older models have external fan blades, while the latest ones come with internal cooling fans.

As we have discussed earlier, an alternator converts mechanical energy into electrical energy and provides your car with all the electricity it needs. Let’s see how exactly this device works:

The working principle of an alternator is identical to that of electromagnetic induction. According to this law, a conductor, a magnetic field, and mechanical energy are required for the production of electricity.

It all begins with the engine. The advanced automobiles have the serpentine belt to drive the alternator by engine’s crankshaft, while older vehicles tend to have a separate pulley running through the crankshaft to the alternator. The movement of the belt provides mechanical energy to spin the rotor within the stator. This spinning of electromagnets of the rotor over copper windings of the stator creates a magnetic field that ultimately generates an AC voltage captured by the stator.

The vehicle cannot use AC electricity because it can flow in different directions. However, it is necessary to convert the AC into DC because car batteries work on a one-way direct current. That’s why, prior to the voltage regulator, the AC electricity is fed to a diode rectifier to turn into DC. After this, the voltage regulator distributes the electricity to the vehicle and regulates the battery’s amount of power.